characteristics of the WIC and Medicaid populations differed considerably
across the study states, and such differences are important factors in the
assessment of the effects of WIC participation.

Specifically, in 1987, the characteristics of the Medicaid-eligible
populations differed considerably across the five study states. Medicaid
beneficiaries in Minnesota were predominantly white and married, were
somewhat older, and had more years of education than those in the other
four states (Devaney et al., 1990). In addition, because of differences in
the income-eligibility standards across the states, the Medicaid populations
in the study states were not comparable socioeconomically. In 1987, the
poverty income threshold for a family of three was $9,056; across the five
study states, the Medicaid income eligibility thresholds ranged from 33
percent of the poverty level in Texas ($2,988 for a family of three) to 88
percent in Minnesota ($7,969 for a family of three). The other three
states had income eligibility thresholds between 40 and 50 percent of the
poverty level. The differences in Medicaid income eligibility across the
states during the study period are likely to have a significant effect on the
study findings and must be considered when the implications of the
analysis findings are assessed. A priori, one would expect that the benefits
of WIC program participation would be greatest among the most severely
disadvantaged women. This expectation is consistent with the apparently
smaller program impact in Minnesota. ‘

The incidence of very low birthweight is also significantly related to the
adequacy of prenatal care, as shown in Appendix Tables A.1-A.3. In all
five states, receiving inadequate versus either adequate or intermediate
levels of prenatal care is associated with a higher likelihood of very low-
birthweight. These findings are consistent with the earlier WIC/Medicaid
study findings that the adequacy of prenatal care is significantly related to
improved birth outcomes, above and beyond the effects of prenatal WIC
participation (Devaney et al., 1990). However, the estimated effects of
receiving intermediate versus adequate levels of prenatal care vary in both
sign and magnitude across the states. In Minnesota, the incidence of very
low birthweight is significantly higher for women receiving intermediate
versus adequate levels of prenatal care, while the opposite is true in
Texas. With the exception of South Carolina, the incidence of very low-
birthweight is significantly higher for women with missing values for the
adequacy of prenatal care index relative to women with adequate levels
of prenatal care.

15



TABLE 3

AVERAGE MEDICAID COSTS AND INFANT MORTALITY

BY BIRTHWEIGHT: MEDICAID NEWBORNS

Very Low Moderately Low Normal
-- Birthweight: Birthweight: Birthweight:
<1,500 Grams —_1,500-2,499 Grams 22,500 Grams
Florida
Average Medicaid Costs $17,677 $5,417 $1,911
Infant Mortality Rate 210.8 16.7 4.7
Minnesota
Average Medicaid Costs $35,106 $10,231 $2,849
Infant Mortality Rate 294.1 44.4 6.1
North Carolina
Average Medicaid Costs $17,315 $4,645 $2,012
Infant Mortality Rate 261.3 25.9 75
South Carolina
Average Medicaid Costs* $20,207 $4,676 $1,702
Infant Mortality Rate 306.1 28.7 7.0
Texas
Average Medicaid Costs $22,224 $7,427 $2,466
Infant Mortality Rate? . 186.3 22.8 4.5

SOURCE: WIC/Medicaid newborn database.

NOTE: Medicaid costs are maternal and newborn costs from birth to 60 days after birth. Medicaid
costs were prorated for claims that extended beyond the first 60 days after birth. Infant
mortality rate is the number of deaths to infants less than 1 year of age (except in Texas)

per 1,000 live births.

*Hospital costs only.

°In Texas, the infant mortality rate refers to deaths to infants less than 6 months of age.



APPENDIX

ESTIMATED PROBIT COEFFICIENTS FOR MODELS OF
VERY LOW BIRTHWEIGHT AMONG MEDICAID NEWBORNS



The estimated number of very low-birthweight births prevented by
prenatal WIC participation by 30 weeks ranges from 191 births in Florida
to 352 births in North Carolina, with intermediate values of 231 births in
Texas and 247 births in South Carolina. Estimated Medicaid cost savings
from the reduction in the incidence of very low-birthweight newborns are
substantial, and are equal to $2.3 million in Florida, $4.5 million in North
Carolina, $3.8 million in South Carolina, and $3.4 million in Texas.



SUMMARY

In summary, prenatal WIC participation in Florida, North Carolina,
South Carolina, and Texas is associated with reductions in the incidence
of very low-birthweight newborns. For women enrolling in the WIC
program by 30 weeks gestation, the estimated reduction in the percent
of live births that were very low birthweight is .6 percentage points in
Florida, 1.7 percentage points in North Carolina, 2.1 percentage points
in South Carolina, and .9 percentage points in Texas. (For women
enrolling by 32 weeks gestation, the estimated reductions in the percent
of live births that were very low birthweight ranges from .7 percentage
points to 2.3 percent percentage points.) While these numbers may
seem small, it is important to remember that very low birthweight is
itself a rare event, and, consequently, these participant-nonparticipant
differences represent large differences in the incidence of very low
birthweight. As shown in Table 6, with the exception of Minnesota,
the estimated number of very low-birthweight births prevented by
prenatal WIC participation by 30 weeks ranges from 191 births in
Florida to 352 births in North Carolina, with intermediate values of 231
births in Texas and 247 births in South Carolina.

As a rough approximation to the savings in Medicaid costs from
participation in the WIC program during pregnancy, the reduction in the
number of very low-birthweight births associated with prenatal WIC
participation can be multiplied by the difference in average Medicaid costs
between very low-birthweight and low-birthweight newborns.! The last
row of Table 6 presents these figures and indicates substantial savings in
newborm and maternal Medicaid costs from birth to 60 days after birth
associated with the reduction in the percentage of very low-birthweight
newborns. Estimated Medicaid cost savings are $2.3 million in Florida,
$4.5 million in North Carolina, $3.8 million in South Carolina, and $3.4
million in Texas.

lThese calculations assume that all very low-birthweight newborns
prevented were moderately low-birthweight newborns. It is likely that at
least some of these births were normal-birthweight newborns, in which
case the savings in Medicaid costs would be larger than those presented
in Table 6.

16



TABLE A2

ESTIMATED PROBIT COEFFICIENTS FOR A MODEL OF THE EFFECT OF
WIC PARTICIPATION BY 32 WEEKS GESTATION ON THE INCIDENCE OF LOW BIRTHWEIGHT

(Standard Errors in Parentheses)

ree
North South
Explanatory Variables Florida Minnesota Carolina Carolina Texas
Intercept -2.163" -2.336 -1.996 4771" -1.893 *
(.102) (171) (101) (147) (076)
Prenatal WIC Participation by 32 -171" -.032 -326* -397" -251"
Weeks Gestation (037) (.068) (.040) (.054) (.044)
Newborn Characteristics
Male -.045 085 -.045 031 -011
(.034) (065) (037) (052) (.038)
Multiple Birth 1.109 926" 1.164" 1.038 1.135"
(.062) (113) (.068) (097) (067)
Mother Characteristics
Age 18-19 -.032 1s -.048 -.094 -126
(.068) (129) (070) (092) (071)
Age 20-34 -.057 -.047 -.004 -174" -.068
(.064) (126) (068) (.084) (.062)
‘Age 35 and over 028 ~.249 137 065 157
(120) (258) (138) (165) (114)
Black® 258° 193 207" 088 -.016
(042) (100) (047) (.069) (050)
Hispanic? -.019 - ~ - -.184 °°
(.074) (047)
Native American - ~322 ~ ~ -
(168)
Asian - -.304 - - .
(198)
Other race/ethnici 110 - - - -364°
(213) (146)
Not married 032 -.039 -.050 070 -010
(042) (078) (048) (065) (.042)
Kessner Index inadequate 305" 340° 515 194 257"
(.048) (106) (.060) (.072) (.052)
Kessner Index intermediate -.064 -.059 222" ~.108 -122°
(041) (084) (043) (182) (.049)
Kessner Index unknown 308 345° 303" -102 244°
(.084) (093) (104) (.063) (068)
Previous live births (number) 004 -.090 -102" ~ -.082*
(014) (.034) (.020) (016)
Pregnancy terminations < 20 ~- 249 - - -
weeks (142)



REFERENCES

Devaney, Barbara, Linda Bilheimer, and Jennifer Schore. "The Savings in Medicaid Costs for
Newborns and Their Mothers From Prenatal Participation in the WIC Program, Volume 1."
U.S. Department of Agriculture, Food and Nutrition Service, Office of Analysis and
Evaluation, October 1990.

"The Savings in Medicaid Costs for Newborns and Their Mothers From Prenatal
Participation in the WIC Program, Volume 2." U.S. Department of Agriculture, Food and
Nutrition Service, Office of Analysis and Evaluation, 1991.

Hughes, Dana, Kay Johnson, Sarah Rosenbaum, and Joseph Liu. The Health of. ‘America’s Children:
Maternal and Child Health Data Book. Washington, D.C., Children’s Defense Fund, 1989.

McCormick, Marie. "The Contribution of Low Birth Weight to Infant Mortality and Childhood
Morbidity.". The New England Journal of Medicine, vol. 312, no. 2, January 10, 1985: 82-90.

National Center for Health Statistics. "Advance Report of Final Mortality Statistics, 1986." Monthly
Vital Statistics Report. vol. 37, no. 6, Supplement, DHHS Pub. No. (PHS) 88-1120. Public
Health Service. Hyattsville, MD, September 1988.

. "Advance Report of Final Natality Statistics, 1987." Monthly Vital Statistics Report. vol.
38, no. 3, Supplement. Public Health Service. Hyattsville, MD: 1989.

Newacheck, Paul. Estimating Medicaid-Eligible Pregnant Women and Children Living Below 185% of
Poverty. Washington, D.C.: National Governor's Association, 1988.

Shapiro, S., M.C. McCormick, B. Starfield, J. Krischer, D. Bross. "Relevance of Correlates of Infant
Deaths for Significant Morbidity at 1 Year of Age." American Journal of Obstetrics and
Gynecology, vol. 136, 1980: 363-373.



Estimated probit coefficients do not have an intuitive interpretation
except to show the direction of the effects of the independent variables
on the likelihood or probability of very low birthweight. However, the
estimated coefficients can be used to calculate the predicted probability
of very low birthweight with and without prenatal WIC participation.
These predicted probabilities are constructed by computing for each
observation the predicted probability that the newborn is very low
birthweight when the WIC participation variable is set equal to 0
(nonparticipant) and when it is set equal to 1 (participant). These
probabilities are then averaged and multiplied by 100 to obtain the
predicted percentage of very low-birthweight newborns with and without
the WIC program. These predicted percentages of very low-birthweight
newborns, as well as the estimated probit coefficients of prenatal WIC
participation, are presented in Table 5. Detailed probit results are
presented in the appendix to this memo.

With the exception of Minnesota, prenatal WIC participation is associated
with a significant decrease in the probability of very low birthweight. (See
Table 5.) The predicted percentages of very low-birthweight newborns for
prenatal WIC participants are roughly half the predicted percentages for
nonparticipants. Using the variable for WIC participation by 32 weeks,
the estimated reduction in the percentage of women who gave birth to
very low-birthweight Medicaid newborns ranges is .7 percentage points in
Florida, 1.1 percentage points in Texas, 2.0 percentage points in North
Carolina, and 2.3 percentage points in South Carolina. When the cutoff
for WIC enrollment is lowered to 30 weeks gestation, the estimated
effects of prenatal WIC participation are reduced slightly, ranging from .6
to 2.1 percentage points, but are still statistically significant. As expected,
the specification that includes all prenatal WIC enrollees as participants
leads to the largest estimated differences in the percentage of very low
birthweight between WIC participants and nonparticipants. However, as
discussed above, these differences are at least partially attributed to
gestational age differences between WIC participants and nonparticipants.

While these results suggest that prenatal WIC participation is associated
with reductions in the percentage of very low-birthweight Medicaid
newborns, significant differences are found in the magnitude of the WIC
effects across the study states. The estimated effects of prenatal WIC
participation by Medicaid beneficiaries on the incidence of very low
birthweight were greatest in North Carolina and South Carolina, while no
Statistically significant effect was found for Minnesota. Interstate
comparisons of study findings must be made cautiously, however, since the

13



identify WIC prenatal participants were not available for births in an
earlier period.

Data from the states’ WIC data systems were used to determine whether
a Medicaid-covered mother was receiving WIC benefits while she was
-pregnant and, if so, the costs of providing the WIC food packages. For
the WIC/Medicaid study, prenatal WIC participation was defined as the
following: for Florida, Minnesota, and North Carolina, if the woman
redeemed at least one food instrument during the nine months prior to
birth; for South Carolina, if she was issued a food instrument during the
nine months prior to birth; and, in Texas, if she had a WIC certification
date sometime during the nine months prior to birth. As discussed in
detail below, the analysis of very low birthweight summarized in this memo
considers alternative definitions of prenatal participation in assessing the
effects of WIC participation on the incidence of very low birthweight.

Data from the Vital Records birth certificate files retained for the study
included: sex, number, duration of gestation, and birthweight of
newborns; age, race, ethnicity, education, and marital status of mothers;
indicators of prenatal care; and number of previous live births and
previous pregnancy terminations. The adequacy of prenatal care was
measured with a modified Kessner Index. The Kessner Index combines
information on the timing of entry into prenatal care with the number of
visits recorded and the length of pregnancy. For a full-term pregnancy,
adequate prenatal care is defined as nine or more visits, with the first visit
occurring during the first trimester of pregnancy, and inadequate care is
defined as four or fewer visits. Intermediate care for a full-term
pregnancy encompasses all levels of prenatal care in between the two
extremes. Adequate prenatal care for preterm births (births of less than
37 weeks gestation) requires a decreasing number of visits as the length
of gestation decreases.

To conduct the analysis of the effects of prenatal WIC participation on
Medicaid costs and birth outcomes, the data on Medicaid costs, WIC
participation, and birth outcomes and prenatal care adequacy were
combined for each Medicaid-covered birth. Overall, the WIC/Medicaid
analysis database includes nearly 105,000 Medicaid births. The proportion
of these births occurring to WIC participants varied across the study
states, ranging from nearly one-half of the Medicaid births in Texas to
almost three-quarters of the Medicaid births in South Carolina.



TABLE A3 (continued)

North South
Explanatory Variables Florida Minnesota Carolina Carolina Texas
Mother Characteristics (continued)
Education < 9 years -.068 47 015 066 -
(087) (218) (.096) (127)
Education 9-11 years -.089 -1S1 ~044 ~.024 -
(.062) (117) (.066) (094)
Education 12 years -.038 059 -.042 ~.024 -
(058) (106) (.060) (089)
Education missing - 264 389 752" -
(137) (366) (228)
Urban 039 -079 060 -.087 -
(.056) (073) (038) (.053)
Prenatal care from public health -.202°* ~ - ~ -
clinic (.060)
Sample Size 11,547

SOURCE: WIC/Medicaid newborn database.

NOTE: The dependent variable is equal to one if newborn birthweight is less than 2,500 grams (5.5 pounds), and equal to zero otherwise.

The unit of observation is the newborn.

*(**): Significant at the .05 (.01) level, two-tailed test.

*Racial/ethnicity groups varied across states. In North Carolina and South Carolina, a small number of women classified neither as white
nor black are included with biack women. In Texas, "black" means "black, nonspanish,” "Hispanic" means "Mexican," and "Other

race/ethnicity" means "other Hispanic.” In Florida, "other race/ethnicity" means "Native American or Asian."



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OVERVIEW OF
THE WIC/
MEDICAID
STUDY

VERY LOW BIRTHWEIGHT AMONG MEDICAID
NEWBORNS IN FIVE STATES: THE EFFECTS
OF PRENATAL WIC PARTICIPATION

This report summarizes the findings from an analysis of very low
birthweight among Medicaid newborns and the effect of prenatal WIC
participation on the likelihood of very low birthweight. The analysis
extends the work conducted under the WIC/Medicaid Study, and is based
on newborn analysis files for five states--Florida, Minnesota, North
Carolina, South Carolina, and Texas.

The report is organized in four sections: the first section provides an
overview of the WIC/Medicaid study; the second section describes the
WIC/Medicaid database; the third section discusses a key analytic issue--
the definition of prenatal WIC participation; and the final section presents
descriptive and multivariate results. An appendix contains tables with
detailed analysis results.

The WIC/Medicaid study examined the relationship between prenatal
WIC participation, Medicaid costs from birth to 60 days after birth, and
a variety of birth outcomes. The birth outcomes included newborn
birthweight, gestational age, the likelihood of low birthweight, and the
likelihood of a preterm birth for Medicaid beneficiaries.

Five states were included in the WIC/Medicaid study--Florida, Minnesota,
North Carolina, South Carolina, and Texas. The study period included all
Medicaid births in 1987 for Florida, Minnesota, North Carolina, and South
Carolina, and all Medicaid births from January through June 1988 in
Texas. As shown in Table 1, the five study states exhibited some striking
contrasts in birth outcomes and perinatal risk factors. Minnesota had
birth outcomes that were more favorable than those of the other study
states. Both its infant mortality rate and percentage of low-birthweight
infants (birthweight of less than 2,500 grams, or 5.5 pounds) were the
lowest of the five states and were lower than the rate for the nation as a
whole. In contrast, all of the three southeastern states--Florida, North
Carolina, and South Carolina--had infant mortality rates that were higher
than the national average. Texas is an extremely large state, accounting
for roughly 8 percent of all U.S. births. In 1987, its infant mortality rate
was below the U.S. average, although a relatively high proportion of
women received late or no prenatal care.



TABLE 5

RESULTS OF AN ANALYSIS OF VERY LOW BIRTHWEIGHT

Percentage of Very Low Birthweight Newborns
Probit Coefficient Without WIC With WIC Difference
Florida
Prenatal WIC Participation -.299°"* 2.7% 1.4% 1.3%
(036)
WIC Participation by 32 Weeks “171 23 16 a
(037)
WIC Participation by 30 Weeks -.130" 22 16 6
(.037)
Minnesota
Prenatal WIC Participation -221" 19% 11% 8%
(067)
WIC Participation by 32 Weeks -.032 15 14 a
(.068)
WIC Participation by 30 Weeks 0005 14 14 0.0
(.068)
North Carolina
Prenatal WIC Participation -.462 49% 19% 3.0%
(039)
WIC Participation by 32 Weeks -326 * 40 20 20
(.040)
WIC Participation by 30 Weeks -.287" 38 21 17
(.040)
South Carolina
Prenatal WIC Participation -515" 49% 16% 3.3%
(054)
WIC Participation by 32 Weeks -.397°" 40 17 23
(054)
WIC Participation by 30 Weeks -.363" 38 17 21
(054)
Texas
Prenatal WIC Participation -.386 2.7% 11% 1.6%
(043)
WIC Participation by 32 Weeks -.251" 24 13 il
(.044)
WIC Participation by 30 Weeks -.228"* 23 14 9
(044)

SOURCE; WIC/Medicaid newborm database.

*(**): Significant at .05(.01) level.

14



WIC/MEDICAID
DATABASE

birthweight and very low-birthweight newborns relative to newborns that
are not low birthweight. One study found that, relative to normal-
birthweight newborns, low-birthweight newborns were 40 times more likely
to die in the neonatal period and very low-birthweight newborns were 200
times more likely to die in the neonatal period (Shapiro et al., 1980).

Given the severe consequences of very low birthweight, an important
policy question is the extent to which very low birthweight can be avoided.
The objective of this study is to examine the determinants of very low
birthweight among Medicaid newborns and to assess the effects of
prenatal WIC participation on the incidence of very low birthweight. The
major goal of the prenatal WIC program is to improve the nutritional
status of participants through the provision of food supplements, nutrition
education, and health and social service referrals to low-income pregnant
women. Prenatal WIC participation may affect the probability of very low
birthweight in two main ways. First, the provision of food supplements
and nutrition education during pregnancy may lead to increased
birthweight, and increases in birthweight should result in a lower
percentage of very low-birthweight newborns. Second, the health and
social service referrals provided by the WIC program staff are expected
to result in increased use of prenatal care, which may have independent
effects on the birthweight distribution of WIC participants.

The database constructed for the WIC/Medicaid study served four
major purposes: (1) to identify Medicaid mothers and newborns, (2) to
provide information on Medicaid costs from birth to 60 days after birth,
(3) to determine whether the mother participated in the WIC program
while she was pregnant, and (4) to provide information on birth
outcomes and on the use of prenatal care. In each state, the analysis
database was constructed from the linkage of three main state data
files--the Medicaid paid claims and eligibility files, the WIC program
files, and the Vital Records files.

Medicaid eligibility and paid claims files served two purposes: (1) to
identify Medicaid-covered births, and (2) to provide data on Medicaid
costs for the analysis. The analysis sample includes all Medicaid-covered
births that occurred in 1987 in Florida, Minnesota, North Carolina and
South Carolina, and those in the first six months of 1988 in Texas. In
Texas, the study is based on all Medicaid births that occurred during the
period from January 1988 through June 1988, since the data necessary to



TABLE Al

ESTIMATED PROBIT COEFFICIENTS FOR A MODEL OF THE EFFECT OF
PRENATAL WIC PARTICIPATION ON THE INCIDENCE OF VERY LOW BIRTHWEIGHT

(Standard Errors in Parentheses)

pT
North South
Explanatory Variables - Florida Minnesota Carolina Carolina Texas
Intercept -2.087 * . 2.214" -1.900 -1.683 ** -1.829 "
(103) (amy (102) (148) (077)
Prenatal WIC Participation -.299 °° -221"" -462"" -515 * -.386 "*
(036) (.067) (039) (054) (043)
Newborn Characteristics
Male -.045 079 -048 029 -013
(035) (.065) (038) (.052) (038)
Multiple Birth 1.107 * 873" 1.160" 1.029 ** 1.142"
(.062) (113) (.068) (.098) (067)
Mother Characteristics
Age 18-19 -.034 017 -051 -.093 -.135
(.068) (130) (071) (093) (071)
Age 20-34 -.056 -.048 -.008 -176" 077
(.064) (126) (.068) (084) (.063)
Age 35 and over 038 -.244 7 054 149
(120) (258) (139) (.166) (114)
Black* 265" 208 * 226" 092 0003
(042) (.200) (047) (.069) (050)
Hispanic* -.020 - ~ ~ 7154"
(074) (.048)
Native American - -302 - ~ -
(167)
Asian - -.264 - - -
(.200)
Other race/ethnicity* 127 ~ - - -.336*
(213) (147)
Not married 033 -.030 -.087 on ~014
(043) (075) (048) (.065) (042)
Kessner Index inadequate 278° 296" 488" 197" 237"
(048) (105) (.060) (072) (.052)
Kessner Index intermediate -.060 -.069 467" -035 ~125°
(416) (.084) (103) (183) (050)
Kessner index unknown 287° 34" 229" -.093 236"
(.085) (092) (047) (064) (.068)
Previous live births (number) 001 -.088 -105 - -.053 *
(014) (034) (.020) (016)
Pregnancy terminations < 20 - 243, - - -
weeks (143)



Contract No: 53-3198-0-033
Subcontract No: 1-524-4790
MPR Reference No: 7939-082

VERY LOW BIRTHWEIGHT AMONG MEDICAID
NEWBORNS IN FIVE STATES: THE EFFECTS
OF PRENATAL WIC PARTICIPATION

Submitted to:

U.S. Department of Agriculture
Food and Nutrition Service

Office of Analysis and Evaluation
3101 Park Center Drive, 2nd Floor
Alexandria, VA: 22302

Project Officer: Dr. Janet Tognetti
Task Leader: Dr. Janet Tognetti

March 1992

Author:

Barbara Devaney

Submitted by:

Mathematica Policy Research, Inc.
P.O. Box 2393

Princeton, NJ 08543-2393

(609) 799-3535

Under Subcontract to the Research
Triangle Institute

Contract Amount: $574,095

Subcontract Amount: $218,255

Fully Competitive



TABLE 2

INCIDENCE OF VERY LOW BIRTHWEIGHT AMONG MEDICAID NEWBORNS BY GESTATIONAL AGE

North South
Florida Minnesota Carolina Carolina Texas
Total
Number of Very Low Birthweight Newborns 778 218 597 294 510
Percent of Live Births 22% 19% 29% 25 % 2.0 %
Gestational Age
Unknown
Number of Very Low Birthweight Newborns 60 4 48 4 68
Percent of Live Births 6.0% 65 % 15 % 49% 4.6%
< 28 Weeks
Number of Very Low Birthweight Newborns 238 69 210 103 175
Percent of Live Births 61.4 % 98.6 % 153 % 81.1 % TBS %
- 28-30 Weeks
Number of Very Low Birthweight Newborns 221 57 141 78 113
Percent of Live Births 48.6 % 79.2% 48.0 % 39.9 % 37.4 %
31-32 Weeks
Number of Very Low Birthweight Newborns 108 13 68 40 3
Percent of Live Births 18.5 % 171% 19.4 % 16.9 % 18.4 %
> 32 Weeks
Number of Very Low Birthweight Newborns 151 38 130 2 81
Percent of Live Births 5% A% 7% 1% 4%

SOURCE: WIC/Medicaid newborn database.

NOTE: Very low birthweight is birthweight less than 1,500 grams, or 3.3 pounds.



PRENATAL WIC
PARTICIPATION

As discussed above, the primary WIC participation variable used in the
WIC/Medicaid study is a simple binary variable that equals one if the
woman participated in the WIC program any time during her pregnancy
and equals zero otherwise. One potential problem with this
specification is that it constrains the effect of prenatal WIC
participation to be the same regardless of when during pregnancy
women enrolled in the WIC program. WIC participants included some
women who enrolled early in pregnancy and some who enrolled late in
pregnancy. The pregnancy outcomes are likely to be more favorable
and Medicaid costs less for the group of later WIC enrollees relative to
early enrollees in the WIC program for reasons that are related mostly
to longer pregnancy durations rather than to WIC participation. In
addition, for the later enrollees, there is the potential for an
overstatement of the effects of prenatal WIC participation since birth
outcomes for late WIC enrollees with longer gestational ages are
compared with the birth outcomes for nonparticipants, some of whom
had low-gestational age births and did not have the opportunity to
enroll later as prenatal WIC participants.

This issue of the timing of prenatal WIC enrollment is particularly
important in the context of an analysis of very low birthweight. As shown
in Table 2, although very low birthweight among Medicaid newborns is a
rare event, ranging from 1.9 percent of Medicaid births in Minnesota to
2.9 percent in North Carolina in 1987, the percentage of Medicaid
newborns that were very low birthweight is strongly related to gestational
age. The vast majority of newborns born at less than 28 weeks gestation
were very low birthweight. In fact, all but one Medicaid newborn in
Minnesota with gestational age less than 28 weeks was very low
birthweight. For newborns born from 28 to 30 weeks gestation, between
40 and 80 percent were very low birthweight. In contrast, the incidence
of very low birthweight for Medicaid newborns with gestational age
greater than 32 weeks was quite low, at roughly .5 percent of such births.

Given this strong relationship between very low birthweight and
gestational age, it is inappropriate to include late prenatal WIC enrollees
as WIC participants. That is, WIC participants who enroll after 32 weeks
will be very unlikely to have very low birthweight newborns simply because
their pregnancies are longer, and it would be incorrect to attribute the
effect of the duration of pregnancy on very low birthweight to WIC
participation.



The data on perinatal risk factors presented in Table 1 are, for the most
part, consistent with the birth outcomes of the five study states. In
particular, Minnesota had very favorable birth outcomes and had both the
lowest percentage of women with incomes below poverty and the lowest
percentage receiving late or no prenatal care. In contrast, South Carolina
~had the highest percentage of women of childbearing age below poverty,
a higher than average percentage receiving late or no prenatal care, and
the highest rates of infant mortality and low birthweight. Such differences
across the study states are very important to consider in interpreting the
WIC/Medicaid study results.

The principal findings from the WIC/Medicaid study indicate considerable
Medicaid cost savings for prenatal WIC participants (Devaney et al., 1990
and 1991). The estimated savings in maternal and newborn Medicaid
costs during the first 60 days after birth associated with prenatal
participation in the WIC program ranged from $277 in Minnesota to $598
in North Carolina, with intermediate values of $347, $493, and $565 in
Florida, Texas, and South Carolina, respectively. The associated ratios of
Medicaid cost savings to WIC program costs ranged from 1.77 in Florida
to 3.13 in North Carolina, indicating that for every dollar spent on the
prenatal WIC program, the associated savings in Medicaid costs for
newborns and mothers during the first 60 days after birth were between
$1.77 (Florida) and $3.13 (North Carolina).

In all five study states, prenatal WIC participation by Medicaid
beneficiaries was associated with increased birthweight and a lower
incidence of low birthweight. The average increase in birthweight related
to prenatal WIC participation by Medicaid beneficiaries ranged from 51
grams in Minnesota to 73 and 77 in Florida and Texas, respectively, to 113
and 117 grams in South Carolina and North Carolina, respectively. In
addition, the estimated reduction in the percentage of Medicaid mothers
who had low-birthweight newborns (birthweight less than 2,500 grams, or
5.5 pounds) attributable to prenatal WIC participation ranged from 2.2
percentage points in Minnesota to 5.1 percentage points in North
Carolina and South Carolina.

One birth outcome not examined in the WIC/Medicaid study is the
incidence of very low birthweight among Medicaid beneficiaries. Very low
birthweight is newborn birthweight less than 1,500 grams (3.3 pounds).
Low birthweight in general, and especially very low birthweight, is a
primary determinant of infant mortality and morbidity (McCormick, 1985).
Neonatal and infant mortality rates are considerably higher for low-



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17



TABLE A.2 (continued)

Explanatory Variables

Florida

Minnesota

North
Carolina

South
Carolina

Mother Characteristics (continued)
Pregnancy terminations > 20
weeks

Education < 9 years

Education 9-11 years

Education 12 years

Education missing

Urban

Prenatal care from public health
clinic

-063
(087)

((062)

-037
(.014)

~.037
(056)

-.194
(060)

139°
(035)

147
(218)
153
(117)
060
(206)
260
(137)

-079
(073)

146
(.028)

020
(100)

-.042
(,066)

-040
(060)

067
(127)

022
(.095)
021
(.090)
742°
(229)

062
(.053)

Sample Size

SOURCE: WIC/Medicaid newborn database.

NOTE: The dependent variable is equal to one if newborn birthweight is less than 2,500 grams (5.5 pounds), and equal to zero otherwise.

The unit of observation is the newborn.

*(**): Significant at the .0S (.01) level, two-tailed test.

*Racial/ethnicity groups varied across states. In North Carolina and South Carolina, a small number of women classified neither as white
In Texas, "black” means “black, nonspanish,” "Hispanic" means "Mexican," and "Other

nor black are included with black women.

race/ethnicity" means "other Hispanic." In Florida, “other race/ethnicity" means "Native American or Asian.”



VERY LOW BIRTHWEIGHT AMONG MEDICAID
NEWBORNS IN FIVE STATES: THE EFFECTS
OF PRENATAL WIC PARTICIPATION

EXECUTIVE SUMMARY

This study is an analysis of very low birthweight among Medicaid
newborns and the effect of prenatal WIC participation on the likelihood
of very low birthweight. The analysis is an extension of the work
conducted under the WIC/Medicaid Study, and is based on newborn
analysis files for five states--Florida, Minnesota, North Carolina, South
Carolina, and Texas. The study period included all Medicaid births in
1987 for Florida, Minnesota, North Carolina, South Carolina, and all
Medicaid births from January through June 1988 in Texas.

Very low birthweight is defined as birthweight of less than 1,500 grams,
or 3.3 pounds. Very low birthweight in the five study states was a rare
event, ranging from 1.9 percent of Medicaid newborns in Minnesota to 2.9
percent in North Carolina during the study period. However, very low-
birthweight newborns were very expensive and had infant mortality rates
that far exceeded those of newborns that were not low birthweight.
Average maternal and newborn Medicaid costs from birth to 60 days after
birth for very low-birthweight newborns were roughly 3 to 4 times the
average for newborns that were moderately low birthweight (1,500 to
2,499 grams) and 9 to 12 times the average for newborns that were not
low birthweight (2,500 grams and over). Infant mortality rates for very
low-birthweight Medicaid newborns ranged from 210.8 infant deaths per
1,000 live births in Florida to 306.1 in South Carolina, compared to a
range of 16.7 to 44.4 for moderately low-birthweight newborns and 4.5 to
7.5 for normal-birthweight newborns.

In Florida, Minnesota, North Carolina, and South Carolina, prenatal WIC
participation is associated with a significant decrease in the probability of
very low birthweight. The predicted percentages of very low-birthweight
Medicaid newborns for prenatal WIC participants are roughly half the
predicted percentages for nonparticipants. For women enrolling in the
WIC program by 30 weeks gestation, the estimated reduction in the
percent of live births that were very low birthweight is .6 percentage
points in Florida, 1.7 percentage points in North Carolina, 2.1 percentage
points in South Carolina, and .9 percentage points in Texas.



TABLE 4

INCIDENCE OF VERY LOW BIRTHWEIGHT AMONG MEDICAID NEWBORNS

North South
Florida Minnesota Carolina Carolina Texas

Total

Number of Very Low Birthweight Newborns 778 218 597 294 510

Percent of Live Births - 22% 19% 29 % 25 % 2.0 %
WIC Participation
Prenatal Participants

Number of Very Low Birthweight Newborns 278 110 250 131 127

Percent of Live Births . 14% 14% 18% 15 % 1.0%
Nonparticipants

Number of Very Low Birthweight Newborns 500 108 347 163 383

Percent of Live Births 33% 29% 5.4% 5.2% 2.9 %
Participants by 32 Weeks

Number of Very Low Birthweight Newborns 269 a1 227 126 124

Percent of Live Births 15% 1.4% 18 % 16 % 12%
Nonparticipants by 32 Weeks

Number of Very Low Birthweight Newborns 509 127 370 168 386

Percent of Live Births 28 % 25 % 44% 43% 25%
Participants by 30 Weeks

Number of Very Low Birthweight Newborns 259 89 27 123 119

Percent of Live Births 16 % 14% 18 % 16 % 13%
Nonparticipants by 30 Weeks ‘

Number of Very Low Birthweight Newborns 519 129 370 im 391

Percent of Live Births 2.7% 24% 44% 4.1% 24%
Race/Ethnicity of Mother*
White

Number of Very Low Birthweight Newborns 242 144 168 57 118

Percent of Live Births 16% 1.6% 22% 1.9% 2.0 %
Black

Number of Very Low Birthweight Newborns 481 29 429 237 165

Percent of Live Births 29% 2.6 % 3.3% 27% 23 %
Hispanic

Number of Very Low Birthweight Newborns 49 - - - 159

Percent of Live Births 15% - - - 1.4 %
Marital Status
Married

Number of Very Low Birthweight Newborns 230 137 162 1 228

Percent of Live Births 18% 2.0 % 25 % 2.0 % 19%
Not Married

Number of Very Low Birthweight Newborns 547 81 435 223 280

Percent of Live Births 24% 1.6 % 3.1% 2.7% 21%



Multivariate
Analysis of Very
Low Birthweight

generally lower than average rates. With the exception of Minnesota,
married mothers had lower rates of very low birthweight than unmarried
mothers, although in Texas the difference was quite small. Differences
observed by age were also small, although the rates of very low
birthweight were generally lowest for women aged 20-34 years. As
-expected, plurality is strongly related to the incidence of very low
birthweight, with multiple births considerably more likely to be very low
birthweight than singleton births. Between 9.6 and 18.3 percent of
multiple births among Medicaid beneficiaries were very low birthweight,
as compared with between 1.7 and 2.5 percent of singleton births.

Substantial differences in the incidence of very low birthweight are
observed for women who differ in the adequacy of prenatal care. In
particular, women who received inadequate levels of prenatal care had
higher rates of very low birthweight than women who received either
intermediate or adequate levels of prenatal care. Interestingly, women
with missing data on the adequacy of prenatal care (because of missing
data on either gestational age, number of prenatal care visits, or the
timing of the first prenatal care visit) also had higher than average rates
of very low birthweight.

The multivariate analysis examines the relationship between the
likelihood of very low birthweight and prenatal WIC participation. The
dependent variable for the analysis is dichotomous, equal to one if
newborn birthweight is less than the cutoff for very low birthweight
(1500 grams) and equal to zero otherwise. Probit, a maximum
likelihood estimation procedure for dichotomous dependent variables,
is used to estimate the state-specific very low-birthweight models.

As discussed previously, different specifications of prenatal WIC
participation were used in the analysis: (1) participation at any time
during pregnancy, (2) participation by 32 weeks gestation, and (3)
participation by 30 weeks gestation. Because the vast majority of very
low-birthweight newborns are also low-gestational age newborns, the first
specification, which includes late WIC enrollees as participants, is
expected to confound WIC effects with gestational age effects and to lead
to an overstatement of the relationship between prenatal WIC
participation and the likelihood of very low birthweight. The results from
this specification are presented primarily to provide a comparison with
more conservative definitions of prenatal WIC participation.

12



Table

TABLES

Page
BIRTH OUTCOMES AND PERINATAL RISK FACTORS:
U.S. AND STUDY STATES .........- 2. eee e eee eee eee 2
INCIDENCE OF VERY LOW BIRTHWEIGHT AMONG
MEDICAID NEWBORNS BY GESTATIONAL AGE .........--+-- 7
AVERAGE MEDICAID COSTS AND INFANT MORTALITY
BY BIRTHWEIGHT: MEDICAID NEWBORNS ..........--+--+-- 9
INCIDENCE OF VERY LOW BIRTHWEIGHT AMONG
MEDICAID NEWBORNS .........--2 0000 ee eee eter rere 10
RESULTS OF AN ANALYSIS OF VERY LOW BIRTH-
WEIGHT ...... 0.2 cece eee eet eee eeenee 14

ESTIMATED SAVINGS IN MEDICAID COSTS FROM
THE PREVENTION OF VERY LOW-BIRTHWEIGHT
MEDICAID NEWBORNS .........- 000 e eee e eee eee eres 17

iii



TABLE A.1 (continued)

North South
Explanatory Variables Florida Minnesota Carolina Carolina Texas
Mother Characteristics (continued) a
Pregnancy terminations > 20 - 139 042 - 214
weeks (035) (035) (059)
Education < 9 years -.056 147 033 083 ~
~ (087) (221) (097) (129)
Education 9-11 years -.081 166 ~.032 -017 ~
(.062) (117) (067) (.096)
Education 12 years -033 065 -031 ~014 -
(058) (107) (061) (.090)
Education missing ~ -260 379 703 * ~
(137) (374) (.230)
Urban 030 -.086 042 -077 -
(056) (073) (.038) (.053)
Prenatal care from public health -.159 ~ ~ -
clinic (061)
Sample Size 11,773

SOURCE: WIC/Medicaid newborn database.

NOTE: The dependent variable is equal to one if newborn birthweight is less than 1,500 grams (3.3 pounds), and equal to zero otherwise.
The unit of observation is the newborn.

*(**): Significant at the .05 (.01) level, two-tailed test.
*Racial/ethnicity groups varied across states. In North Carolina and South Carolina, a small number of women classified neither as white

nor black are included with black women. In Texas, "black" means "black, nonspanish," "Hispanic" means "Mexican," and "Other
race/ethnicity" means "other Hispanic." In Florida, “other race/ethnicity" means "Native American or Asian."



CONTENTS

Page
OVERVIEW OF THE WIC/MEDICAID STUDY ..........--- 022s eee ee eee eee 1
WIC/MEDICAID DATABASE ..... 2.02 een eet een n nee 4
PRENATAL WIC PARTICIPATION .. 1... 00-1 e eee eee eee e eee 6
EMPIRICAL RESULTS ... 0.0.60 n een e nee eee 8
SUMMARY 2.02... cece teen eee n ene e tenet eee 16
REFERENCES .. «2. eee ete e ene ee eee 18

APPENDIX A: ESTIMATED PROBIT COEFFICIENTS FOR MODELS OF
VERY LOW BIRTHWEIGHT AMONG MEDICAID NEWBORNS



TABLE A3

ESTIMATED PROBIT COEFFICIENTS FOR A MODEL OF THE EFFECT OF
WIC PARTICIPATION BY 30 WEEKS GESTATION ON THE INCIDENCE OF LOW BIRTHWEIGHT

(Standard Errors in Parentheses)

North South
Explanatory Variables Florida Minnesota Carolina Carolina Texas
Intercept -2.186 -2.356 -2.023 “1.797 -1.905 **
(102) (171) (101) (146) (076)
Prenatal WIC Participation by 30 -130 7 0005 287 * 3637 -.228 *
Weeks Gestation (.037) (068) (040) (054) (044)
Newborn Characteristics
Male -.044 086 -.046 031 -011
(034) (.065) (037) (052) (.038)
Multiple Birth 1.105 * 933" 1.164" 1.046 1.133"
(.062) (113) (067) (097) (067)
Mother Characteristics
Age 18-19 -031 016 -.046 -.094 -123,
(.068) (129) (070) (092) (070)
Age 20-34 -.0S7 -.047 -.001 171" -.066
(.063) (126) (.067) (083) (.062)
Age 35 and over 024 -.250 148 061 159
(119) (259) (138) (465) (113)
Black* 256 "* 189 203° 087 -019
(042) (100) (046) (.069) (.050)
Hispanic* -.018 - - - -.189*
(074) (047)
Native American - -327 - - -
(168)
Asian ~ -313 - - -
(198)
Other race/ethnicity* 103 ~ - - -.370"
(.214) (146)
Not married 032 ~041 ~.051 O71 -.008
(042) (075) (048) (065) (042)
Kessner Index inadequate 316° 350° 529" 194" 260"
(.049) (.106) (.060) (072) (051)
Kessner Index intermediate -.064 -.056 219" -.096 -123°
(041) (084) (.043) (181) (049)
Kessner Index unknown 314" 353" 330" --106 -245"*
(.084) (093) (104) (.063) (.068)
Previous live births (number) 005 -.090 -101 - -052
(014) (034) (019) (016)
Pregnancy terminations < 20 - 250 - - -
weeks (142)
Pregnancy terminations > 20 - 139° 146° ~ 204 **
weeks (.035) (028) (058)



EMPIRICAL
RESULTS

Descriptive
Analysis of Very
Low Birthweight

To account for the relationship between gestational age and the incidence
of very low birthweight, we consider two alternative definitions of prenatal
WIC participation: (1) WIC participation by 32 weeks gestation, and (2)
WIC participation by 30 weeks gestation. Specifically, participants who
enrolled in the WIC program after 32 weeks gestation in the first case and
30 weeks in the second case were considered nonparticipants.

This section describes the results from descriptive and multivariate
analyses of very low birthweight among Medicaid newborns. The
descriptive analysis examines the incidence of very low birthweight and
selected characteristics of very low-birthweight newborns, low-
birthweight newborns, and normal-birthweight newborns. The
multivariate analysis examines the relationship between very low
birthweight and prenatal WIC participation when other factors are
controlled for.

As discussed above, very low birthweight in the five WIC/Medicaid
study states was a rare event, ranging from 1.9 percent of Medicaid
newborns in Minnesota to 2.9 percent in North Carolina during the
study period. However, very low birthweight newborns were very
expensive and had infant mortality rates that far exceeded those of
newborns that were not very low birthweight, as shown in Table 3.
Average maternal and newborn Medicaid costs from birth to 60 days
after birth for very low birthweight newborns were roughly 3 to 4 times
the average for newborns that were moderately low birthweight (1500
to 2499 grams) and 9 to 12 times the average for newborns that were
not low birthweight (2500 grams and over). Infant mortality rates for
very low birthweight newborns ranged from 210.8 infant deaths per
1,000 live births in Florida to 306.1 in South Carolina, compared to a
range of 16.7 to 44.4 for moderately low-birthweight newborns and 4.5
to 7.5 for normal-birthweight newborns.

Descriptive data on the incidence of very low birthweight are presented
in Table 4. The percentage of Medicaid newborns who were very low-
birthweight was lower for prenatal WIC participants than for
nonparticipants, regardless of the measure of prenatal WIC participation.
In all five states, Medicaid mothers who did not participate in the WIC
program during pregnancy were approximately two to three times as likely
to have had very low-birthweight newborns as WIC participants. The
incidence of very low-birthweight also varied by race, with blacks having
higher than average rates of very low birthweight and Hispanics having

8



TABLE 4 (continued)

North South
Florida Minnesota Carolina Carolina Texas
‘Age of Mother
< 18 Years of Age
Number of Very Low Birthweight Newborns 94 20 mn 50 66
Percent of Live Births 22% 2.2% 32% 33% 23%
. 18-19 Years of Age .
Number of Very Low Birthweight Newborns 120 52 108 61 87
Percent of Live Births 20 % 2.6 % 28 % 2.6 % 18 %
20-34 Years of Age :
Number of Very Low Birthweight Newborns 537 141 381 173 329
Percent of Live Births 22% 1.7% 2.8 % 23% 1.9 %
35 Years and Older
Number of Very Low Birthweight Newborns 27 5 7 10 2B
Percent of Live Births 23% 1.0% 35% 3.6 % 3.0 %
Kessner Index
Unknown
Number of Very Low Birthweight Newborns 56 B 21 8 64
Percent of Live Births 48% 45 % 55% 3.7% 3.1%
Inadequate
Number of Very Low Birthweight Newborns 222 31 124 96 162
Percent of Live Births 4.2% 27% 6.6 % 4.7 % 3.2%
Intermediate
Number of Very Low Birthweight Newborns 250 45 109 141
Percent of Live Births 15 % 11% 3.2% 19% 13 %
Adequate
Number of Very Low Birthweight Newborns 250 64 182 81 143
Percent of Live Births 19% 13% 18% 2.2% 1.8 %
Plurality
Singleton
Number of Very Low Birthweight Newborns 647 189 494 250 415
Percent of Live Births 19% 1.7% 25 % 2.2% 1.7%
Multiple Birth
Number of Very Low Birthweight Newborns 131 29 103 44 95
Percent of Live Births 14.7 % 9.6 % 183 % 15.3 % 14.4%

SOURCE: WIC/Medicaid newborn database
NOTE: Very low birthweight is birthweight less than 1,500 grams, or 3.3 pounds.

*Racial/ethnicity groups varied across states. In North Carolina and South Carolina, a small number of women classified neither as white
nor biack are included with black women. In Texas, "black" means "black, nonspanish."

set