NCHS Data Brief ■ No. 200 ■ May 2015

u.s. department of health and human services

centers for disease control and prevention

national center for health statistics

When Are Babies Born: Morning, Noon, or Night?

Birth Certificate Data for 2013

T.J. Mathews, M.S.; and Sally C. Curtin, M.A.

Key findings 

Data from the National 

Vital Statistics System

● The highest percentages 

of births occurred during the 

morning and midday hours. 

● Births on Saturday and 

Sunday were more likely to 

occur in the late evening and 

early morning hours than births 

Monday through Friday.

● Compared with induced 

vaginal deliveries and 

noninduced vaginal deliveries, 

cesarean deliveries were the 

least likely to occur during the 

evening and early morning.

● Noninduced vaginal births 

were more likely than cesarean 

and induced vaginal births to 

occur in the early morning.

● Cesarean deliveries with no 

trial of labor were much more 

concentrated during the day 

than were cesarean deliveries 

with a trial of labor.

● Births delivered in hospitals 

and all births show similar 

time-of-day patterns.

As the use of medical interventions for childbirth (i.e., induction of labor and 

cesarean delivery) has increased during the last few decades, an increasing 

proportion of deliveries occur during regular daytime hours (1,2). Hospital 

personnel resources and maternal and newborn outcomes can be influenced by 

the time of day of delivery (3–7). Data on the time of day of the birth became 

available with the 2003 revision of the birth certificate. This report examines 

2013 birth certificate data from the National Vital Statistics System (NVSS) to 

describe the time of day of birth by method of delivery and place of birth for 

a 41-state and District of Columbia (DC) reporting area that had adopted the 

2003 revised birth certificate by January 2013. This reporting area represents 

90% of U.S. births.

Keywords: time of day of birth • cesarean • trial of labor

Newborns were most likely to be delivered during daytime 

hours.

Figure 1. Percent distribution of births, by hour and day of the week of delivery: 41 states and the 

District of Columbia, 2013

NOTES: The differences in the percent distributions are statistically significant. Access data table for Figure 1 at: 

http://www.cdc.gov/nchs/data/databriefs/db_200_table.pdf#1.

SOURCE: CDC/NCHS, National Vital Statistics System. Percent

0

2

4

6

8

6 a.m. 9 a.m. Noon 3 p.m. 6 p.m. 9 p.m. Midnight 3 a.m.

Hour

Total

Average: 4.2%

Monday–Friday

Saturday and Sunday
NCHS Data Brief ■ No. 200 ■ May 2015

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● If births were equally timed throughout the day, an average of 4.2% of newborns would be 

delivered each hour. However, the percentage of deliveries is higher than 4.2% for each hour 

from 8:00 a.m. through 5:59 p.m. for all days of the week (Figure 1). 

● The highest percentages of births occurred during the 8:00 a.m. (6.3%) and noon (6.0%)

hours.

● In contrast, less than 3.0% of infants were born during each hour from midnight through 

6:59 a.m.

● While weekdays show a similar pattern in the timing of births as for all births, weekend 

days show a more evenly distributed pattern of births throughout the day.

● Births on Saturday and Sunday were more likely than those Monday through Friday to occur 

in the late evening and early morning hours from 11:00 p.m. through 5:59 a.m.

Time-of-birth patterns differed markedly by method of delivery. 

● Compared with induced vaginal deliveries and noninduced vaginal deliveries, cesarean 

deliveries were the least likely to occur during the evening and early morning hours 

(Figure 2). Cesarean deliveries peaked during the 8:00 a.m. hour (11.6%) and had another 

smaller peak during the noon hour (7.4%).

● Noninduced vaginal deliveries were more likely to occur from 11:00 p.m. through 6:59 a.m. 

than were induced vaginal deliveries or cesarean deliveries. Noninduced vaginal deliveries 

had the most even distribution across the hours of the day, fluctuating close to the average of 

4.2%.

● In contrast, induced vaginal deliveries rose in the morning hours, peaked in the 3:00 p.m. 

hour, and then declined from 6:00 p.m. onward.

Percent

Figure 2. Percent distribution of births, by hour and method of delivery and induction status: 41 states and the District of 

Columbia, 2013

NOTES: The differences in the percent distributions are statistically significant. Access data table for Figure 2 at: 

http://www.cdc.gov/nchs/data/databriefs/db_200_table.pdf#2.

SOURCE: CDC/NCHS, National Vital Statistics System.

0

2

4

6

8

10

12

6 a.m 9 a.m. Noon 3 p.m. 6 p.m. 9 p.m. Midnight 3 a.m.

Hour

Cesarean delivery

Induced vaginal delivery

Noninduced 

vaginal delivery
NCHS Data Brief ■ No. 200 ■ May 2015

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Cesarean deliveries with no trial of labor were most likely to occur in the 

morning and midday hours.

● The percentage of births occurring during the 8:00 a.m. hour (14.3%) for cesareans with no 

trial of labor was more than three times as high as for cesareans with a trial of labor (4.0%) 

(Figure 3). 

● Cesarean births with no trial of labor peaked during the 8:00 a.m. hour and then, to a lesser 

extent, during the noon hour. In contrast, the percentage of births for cesareans with a trial 

of labor generally rose throughout the day, starting at 6:00 a.m. and peaking from 5:00 p.m. 

through 6:59 p.m. 

● Cesareans with a trial of labor were more likely to be delivered from 4:00 p.m. through 

5:59 a.m. compared with cesareans without a trial of labor, with the largest differences seen 

during the evening hours from 6:00 p.m. through 11:59 p.m.

Percent

Figure 3. Percent distribution of births via cesarean delivery, by hour of delivery and whether trial of labor was attempted: 

41 states and the District of Columbia, 2013

NOTES: The differences in the percent distributions are statistically significant. Access data table for Figure 3 at: 

http://www.cdc.gov/nchs/data/databriefs/db_200_table.pdf#3.

SOURCE: CDC/NCHS, National Vital Statistics System.

6 a.m 9 a.m. Noon 3 p.m. 6 p.m. 9 p.m. Midnight 3 a.m.

Hour

0

2

4

6

8

10

12

14

16

No trial of labor attempted 

Trial of labor attempted
NCHS Data Brief ■ No. 200 ■ May 2015

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Out-of-hospital births were most likely to occur in the early morning. 

● Births delivered in hospitals, which make up more than 98% of deliveries in the reporting 

area, and all births show similar time-of-day patterns, with peaks during the 8:00 a.m. 

(6.3%) and noon (6.1%) hours. Declines in the percentages of deliveries in hospitals are 

observed from 6:00 p.m. through 5:59 a.m. (Figure 4).

● Out-of-hospital deliveries showed a unique pattern by time of day. The percentage of 

deliveries declined during the hours of 6:00 a.m. through 2:59 p.m., with one uptick at noon, 

and increased from 3:00 p.m. through 3:59 a.m., with a brief dip at midnight.

● Births delivered out of hospital were most likely to occur in the early morning hours of 

1:00 a.m. through 4:59 a.m. During these same hours, the lowest percentages were observed 

for in-hospital births.

Percent

Figure 4. Percent distribution of births, by hour and place of delivery: 41 states and the District of Columbia, 2013

NOTES: The differences in the percent distributions are statistically significant. Access data table for Figure 4 at: 

http://www.cdc.gov/nchs/data/databriefs/db_200_table.pdf#4.

SOURCE: CDC/NCHS, National Vital Statistics System.

6 a.m 9 a.m. Noon 3 p.m. 6 p.m. 9 p.m. Midnight 3 a.m.

Hour

0

2

4

6

8

In hospital

Out of hospital
NCHS Data Brief ■ No. 200 ■ May 2015

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Summary

This report presents new data from birth certificates for a 41-state and DC reporting area (90% of 

U.S. births) on the time of day of birth. Differences in the likelihood of delivery during the day 

are partly due to childbirth interventions such as cesarean delivery and induction of labor. Three 

distinct patterns in time of birth are evident for cesarean delivery, induced vaginal deliveries, 

and noninduced vaginal deliveries. Cesarean deliveries without a trial of labor and deliveries in 

hospitals exhibited distinct peaks at 8:00 a.m.–8:59 a.m. and noon–12:59 p.m. and were both 

concentrated during daytime hours. Vaginal births, particularly those that were noninduced, 

were more likely than cesarean births to occur during the late evening and early morning hours, 

although the majority were still delivered in the daytime. Births in out-of-hospital settings were 

most likely to occur in the early morning, starting at 1:00 a.m. In general, these births have fewer 

interventions (8), and thus likely exhibit a more natural time-of-day delivery pattern compared 

with births delivered in hospitals.

Because the data in this report represent 90% of all U.S. births, the results may not be 

generalizable to the United States as a whole. Time-of-birth data will be available for the entire 

United States in 2016.

Definitions

Time of day of birth: Reported on the birth certificate in 1-minute increments. Time-of-birth 

data in this report are grouped according to 24 1-hour increments, and time is grouped into the 

following categories: 

 Morning hours: 6:00 a.m.–11:59 a.m.

 Afternoon hours: 12:00 p.m.–5:59 p.m.

 Evening hours: 6:00 p.m.–11:59 p.m.

 Early morning hours: 12:00 a.m.–5:59 a.m.

 Daytime hours: 6:00 a.m.–5:59 p.m.

Vaginal birth: Delivery of the entire fetus through the vagina. 

Induction of labor: Initiation of uterine contractions by medical and/or surgical means for the 

purpose of delivery before the spontaneous onset of labor (i.e., before labor has begun). 

Cesarean birth and trial of labor

 Cesarean: Extraction of the fetus, placenta, and membranes through an incision in the 

 maternal abdominal and uterine walls. 

 If a cesarean birth is indicated, then the following question is asked: “If cesarean, was a 

 trial of labor attempted?” 

 Trial of labor: Labor was allowed, augmented, or induced with plans for a vaginal 

 delivery.
NCHS Data Brief ■ No. 200 ■ May 2015

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Data source and methods

This report contains data from the Natality Data File from the NVSS, which includes information 

for 41 states and DC, representing 90% of all births occurring in the United States. A description 

of the reporting area is given in the User Guide to the 2013 Natality Public Use File, available 

from: ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Dataset_Documentation/DVS/natality/

UserGuide2013.pdf. Data for 2013 and earlier years may also be accessed from the interactive 

data access tool, VitalStats, available from: http://www.cdc.gov/nchs/VitalStats.htm.

All statements in the text on the differences and distributions of births by time of day are 

statistically significant. Differences were tested at the 0.01 level using two-sided significance tests 

(z tests). Distributions were tested at the 0.05 level using a chi-square test.

About the authors

T.J. Mathews and Sally C. Curtin are with CDC’s National Center for Health Statistics, Division 

of Vital Statistics.
NCHS Data Brief ■ No. 200 ■ May 2015

■  7  ■

References

1. Martin JA, Hamilton BE, Osterman MJK, et al. Births: Final data for 2013. National vital 

statistics reports; vol 64 no 1. Hyattsville, MD: National Center for Health Statistics. 2015.

2. Bernis C, Varea C. Hour of birth and birth assistance: From a primate to a medicalized 

pattern? Am J Hum Biol 24(1):14–21. 2012.

3. Pasupathy D, Wood AM, Pell JP, Fleming M, Smith GC. Time of birth and risk of neonatal 

death at term: Retrospective cohort study. BMJ 341:c3498. 2010.

4. Wu YW, Pham TN, Danielsen B, Towner D, Smith L, Johnston SC. Nighttime delivery and 

risk of neonatal encephalopathy. Am J Obstet Gynecol 204(1):37.e1–6. 2011.

5. Woodhead N, Lindow S. Time of birth and delivery outcomes: A retrospective cohort study. 

J Obstet Gynaecol 32(4):335–7. 2012.

6. Kalogiannidis I, Margioula-Siarkou C, Petousis S, Goutzioulis M, Prapas N, 

Agorastos T. Infant births during the internal night are at increased risk for operative delivery 

and NICU admission. Arch Gynecol Obstet 284(1):65–71. 2011.

7. Gijsen R, Hukkelhoven CW, Schipper CM, Ogbu UC, de Bruin-Kooistra M, Westert G. 

Effects of hospital delivery during off-hours on perinatal outcome in several subgroups: 

A retrospective cohort study. BMC Pregnancy Childbirth 12:92. 2012.

8. MacDorman MF, Mathews TJ, Declercq E. Trends in out-of-hospital births in the United 

States, 1990–2012. NCHS data brief, no 144. Hyattsville, MD: National Center for Health 

Statistics. 2014.
NCHS Data Brief ■ No. 200 ■ May 2015

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Suggested citation

Mathews TJ, Curtin SC. When are babies 

born: Morning, noon, or night? Birth 

certificate data for 2013. NCHS data brief, 

no 200. Hyattsville, MD: National Center 

for Health Statistics. 2015.

Copyright information

All material appearing in this report is in 

the public domain and may be reproduced 

or copied without permission; citation as to 

source, however, is appreciated.

National Center for Health 

Statistics

Charles J. Rothwell, M.S., M.B.A., Director

Nathaniel Schenker, Ph.D., Deputy Director

Jennifer H. Madans, Ph.D., Associate 

Director for Science

Division of Vital Statistics

Delton Atkinson, M.P.H., M.P.H., P.M.P., 

Director

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