this study was developed and approved by the steering committee of the translating research into action for diabetes ( triad ) study and conducted in one of triad 's six translational research centers , kpnc . kpnc is a group practice , prepaid health plan that provides comprehensive medical services through 17 hospitals and 23 outpatient clinics to > 3 million members located in a 14-county region in northern california ( 30% of the general population in the geographic areas covered ) . the kpnc membership closely approximates the population living in the same geographic area demographically except with respect to income : kpnc members underrepresent the very poor and the very wealthy ( 9,10 ) . upon comparison with regional birth certificates over a 14-year period , there were no meaningful differences between women who delivered at a kpnc hospital and women who delivered in the underlying region regarding age at delivery or race , except that women who delivered at a kpnc hospital were slightly less likely to be hispanic ( 25.8 vs. 32.0% ) . we used the kpnc gdm registry ( 11 ) to identify women with gdm who delivered between 1 january 1995 and 31 december 2006 . during this 12-year period , the proportion of women who had been screened for gdm with a 50-g , 1-h oral challenge test during the second trimester increased by 3% over time ( age- and race / ethnicity - adjusted proportions 92.5 [ 95% ci 92.392.7 ] in 19951997 vs. 95.7 [ 95.695.9 ] in 20042006 ) . if results were abnormal ( 1-h plasma glucose levels 7.8 mmol / l [ 140 mg / dl ] ) , this test was followed by a standard diagnostic 100-g , 3-h ogtt . we identified 14,448 pregnancies that had a diagnosis of gdm from a health provider and with plasma glucose results during the index pregnancy that met the national diabetes data group ( nddg ) criteria on the 3-h 100-g ogtt for gdm , i.e. , 2 glucose values at or exceeding the following thresholds : fasting , 105 mg / dl ; 1 h , 190 mg / dl ; 2 h , 165 mg / dl ; and 3 h , 145 mg / dl ( 12,13 ) without recognized preexisting diabetes ( 14 ) . we included only women who met the nddg criteria of gdm because , in this clinical setting , the nddg criteria were used for diagnosis of gdm until january 2007 . approximately 550 women had no diagnosis of gdm but met the nddg criteria ( equivalent to 4% of the size of our gdm cohort with a diagnosis ) ; women without a diagnosis of gdm were excluded from the analysis . for the first and second aims , the primary outcome was performance of postpartum screening for diabetes by either an fpg test alone or a 75-g , 2-h ogtt . because several weeks may elapse before glucose metabolism returns to normal in most women with gdm ( 15 ) , the american diabetes association ( 16 ) and the american college of obstetricians and gynecologists ( 17 ) both recommend that postpartum glucose screening be performed at 6 weeks postpartum or later . we considered the postpartum screening performed only if it was done during the first year after delivery starting from 6 weeks and if the woman was not pregnant again . for the third aim , the outcome was the proportion of women identified with either ifg ( defined as an fpg 100 mg / dl but < 126 mg / dl ) or diabetes diagnosed by fpg 126 mg / dl ( 18 ) . among women who had postpartum screening , therefore , when we report on trends in postpartum conversion to diabetes , we report only on the fasting values detected by either an fpg or an ogtt . for the fourth aim , we examined the proportion of women who were identified as having pre - diabetes on the postpartum screen ( that included ifg as defined above and impaired glucose tolerance [ igt ] defined as a 2-h plasma glucose value 140 mg / dl ) or diabetes ( defined as an fpg > 126 mg / dl or a 2-h plasma glucose value 200 mg / dl ) ( 18 ) . age , gestational age at delivery , race / ethnicity , maternal body weight during the beginning of the second trimester , and gestational age at gdm diagnosis were ascertained from the computerized medical records at birth . use of insulin or glyburide during pregnancy was obtained from the pharmacy database . because we had data on body weight but not on height , a woman was considered obese if her weight was 90th percentile of the weight distribution of women of her race / ethnicity in this study population . macrosomia was defined as birth weight > 4,000 g. data on annual household income were based on census block data . education and parity were obtained by linkage with the state of california birth certificate database . because the lag time before state birth certificates became available is 3 years , we have these variables for women who delivered between 1995 and 2004 . the yearly age- and race / ethnicity - adjusted proportion of women with gdm who had postpartum glucose screening and 95% cis were calculated by the direct method , in which the age and race / ethnicity distribution of the entire study population was used as the standard . among women who had postpartum screening , the direct method was used to calculate the yearly age- and race / ethnicity - adjusted rates of ifg and diabetes diagnosed by fpg . predictors of postpartum screening were examined in a multivariable logistic regression model adjusted for age , race / ethnicity , education , income , obesity , parity , gestational age at gdm diagnosis , glyburide and insulin use during pregnancy , a macrosomic infant at the index pregnancy , visits to an internal medicine or obstetrics / gynecology provider during the postpartum period , year of delivery , and medical facilities . sas ( version 9.1 ; sas institute , cary , nc ) was used for all analyses . this study was approved by the human subjects committee of the kaiser foundation research institute . the yearly age- and race / ethnicity - adjusted proportion of women with gdm who had postpartum glucose screening and 95% cis were calculated by the direct method , in which the age and race / ethnicity distribution of the entire study population was used as the standard . among women who had postpartum screening , the direct method was used to calculate the yearly age- and race / ethnicity - adjusted rates of ifg and diabetes diagnosed by fpg . predictors of postpartum screening were examined in a multivariable logistic regression model adjusted for age , race / ethnicity , education , income , obesity , parity , gestational age at gdm diagnosis , glyburide and insulin use during pregnancy , a macrosomic infant at the index pregnancy , visits to an internal medicine or obstetrics / gynecology provider during the postpartum period , year of delivery , and medical facilities . sas ( version 9.1 ; sas institute , cary , nc ) was used for all analyses . this study was approved by the human subjects committee of the kaiser foundation research institute . we identified 14,448 pregnancies complicated by gdm occurring between 1995 and 2006 among kpnc members who were aged 1544 years and delivered live infants or had still births . these pregnancies occurred among 13,547 women , because 901 had more than one pregnancy during the 12-year study period . the percentage of women with gdm pregnancies who received a postpartum glucose screening test increased from 1995 ( 20.3% ) to 2006 ( 55.9% ) . between 1995 and 2006 , the age of women with gdm increased slightly ( 28.2  5.7 to 28.8  6.0 years ) and the proportion of women with gdm who were hispanic increased markedly . the race / ethnicity distributions in 1995 versus 2006 were as follows : 60.7 and 43.4% white , 14.5 and 15.4% asian , 14.1 and 24.9% hispanic , 6.7 and 6.7% african american , 2.0 and 4.4% other , and 2.0 and 5.2% unknown . changes in the demographics represent changes in the entire population with gdm , regardless of performance of diagnostic screening . after adjustment for age and race / ethnicity , the proportion of women with gdm who received a postpartum glucose screening increased steadily over time from 20.7% ( 95% ci 17.823.5 ) in women who delivered in 1995 to 53.8 ( 51.356.3 ) in women who delivered in 2006 ( fig . unadjusted characteristics of women by postpartum screening status are illustrated in table 1 . in a multiple - adjusted logistic regression model ( table 2 ) , older age , asian or hispanic race / ethnicity , higher education , at least two prior births , earlier gestational age at gdm diagnosis , use of insulin or glyburide during pregnancy , and visits to an internal medicine or obstetrics / gynecology provider during the postpartum period were independent and significant predictors of postpartum screening . obesity and higher parity were significantly associated with less frequent screening . on the basis of fpg ( either performed alone or as part of the ogtt ) , 3.5% ( n = 191 ) had diabetes and 22.0% ( n = 1,228 ) had ifg . the proportion of women with ifg postpartum remained similar over time , but the proportion of women with diabetes decreased from 19951997 to 19982000 and then leveled off ( fig . 564 were screened at postpartum , and 131 had ifg and 32 had diabetes by fpg ( age- and race / ethnicity - adjusted rates 24.2 [ 95% ci 20.27.8 ] and 6.1 [ 4.28.1 ] , respectively ) . among women who delivered in 20042006 , 2,381 women were screened , and 583 had ifg and 80 had diabetes by fpg ( age- and race / ethnicity - adjusted rates 24.3 [ 22.626.0 ] and 3.3 [ 2.64.0 ] , respectively ) . the proportion of women receiving an ogtt increased from 1995 ( 5.0% ) to 2005 ( 16.6% ) and markedly increased in 2006 ( 71.5% ) . in 2006 , kpnc instituted a nurse managed care program that included greater attention to postpartum screening guidelines . among the 600 women who underwent a 75-g ogtt in 2006 , 16 had diabetes at postpartum . diabetes was diagnosed in 4 ( 25% ) by fpg alone . of the remaining 12 women , of the 188 women who were found to have pre - diabetes ( i.e. , either ifg or igt according to the fasting or 2-h glucose values measured during the 75-g ogtt ) , only 114 ( 60% ) were diagnosed with ifg ; 74 ( 40% ) would have been classified as having normal glucose tolerance on the basis of fpg alone . therefore , 78 ( 38% ) of the 204 women with either diabetes or pre - diabetes were identified only by the 2-h glucose measurements . we identified 14,448 pregnancies complicated by gdm occurring between 1995 and 2006 among kpnc members who were aged 1544 years and delivered live infants or had still births . these pregnancies occurred among 13,547 women , because 901 had more than one pregnancy during the 12-year study period . the percentage of women with gdm pregnancies who received a postpartum glucose screening test increased from 1995 ( 20.3% ) to 2006 ( 55.9% ) . between 1995 and 2006 , the age of women with gdm increased slightly ( 28.2  5.7 to 28.8  6.0 years ) and the proportion of women with gdm who were hispanic increased markedly . the race / ethnicity distributions in 1995 versus 2006 were as follows : 60.7 and 43.4% white , 14.5 and 15.4% asian , 14.1 and 24.9% hispanic , 6.7 and 6.7% african american , 2.0 and 4.4% other , and 2.0 and 5.2% unknown . changes in the demographics represent changes in the entire population with gdm , regardless of performance of diagnostic screening . after adjustment for age and race / ethnicity , the proportion of women with gdm who received a postpartum glucose screening increased steadily over time from 20.7% ( 95% ci 17.823.5 ) in women who delivered in 1995 to 53.8 ( 51.356.3 ) in women who delivered in 2006 ( fig . unadjusted characteristics of women by postpartum screening status are illustrated in table 1 . in a multiple - adjusted logistic regression model ( table 2 ) , older age , asian or hispanic race / ethnicity , higher education , at least two prior births , earlier gestational age at gdm diagnosis , use of insulin or glyburide during pregnancy , and visits to an internal medicine or obstetrics / gynecology provider during the postpartum period were independent and significant predictors of postpartum screening . on the basis of fpg ( either performed alone or as part of the ogtt ) , 3.5% ( n = 191 ) had diabetes and 22.0% ( n = 1,228 ) had ifg . the proportion of women with ifg postpartum remained similar over time , but the proportion of women with diabetes decreased from 19951997 to 19982000 and then leveled off ( fig . 564 were screened at postpartum , and 131 had ifg and 32 had diabetes by fpg ( age- and race / ethnicity - adjusted rates 24.2 [ 95% ci 20.27.8 ] and 6.1 [ 4.28.1 ] , respectively ) . among women who delivered in 20042006 , 2,381 women were screened , and 583 had ifg and 80 had diabetes by fpg ( age- and race / ethnicity - adjusted rates 24.3 [ 22.626.0 ] and 3.3 [ 2.64.0 ] , respectively ) . the proportion of women receiving an ogtt increased from 1995 ( 5.0% ) to 2005 ( 16.6% ) and markedly increased in 2006 ( 71.5% ) . in 2006 , kpnc instituted a nurse managed care program that included greater attention to postpartum screening guidelines . among the 600 women who underwent a 75-g ogtt in 2006 , 16 had diabetes at postpartum . diabetes was diagnosed in 4 ( 25% ) by fpg alone . of the remaining 12 women , 8 ( 50% ) had ifg and 4 ( 25% ) had normal fpg . of the 188 women who were found to have pre - diabetes ( i.e. , either ifg or igt according to the fasting or 2-h glucose values measured during the 75-g ogtt ) , only 114 ( 60% ) were diagnosed with ifg ; 74 ( 40% ) would have been classified as having normal glucose tolerance on the basis of fpg alone . therefore , 78 ( 38% ) of the 204 women with either diabetes or pre - diabetes were identified only by the 2-h glucose measurements . in a managed care plan with a large number of women with gdm pregnancies , we found that between 1995 and 2006 , screening for postpartum diabetes increased from 20.7 to 53.8% . the increase in screening performance is not likely to be due to advancing maternal age or changes in the racial / ethnic composition of women with gdm , as this trend in screening performance was similar after adjustment for age and race / ethnicity , and almost the entire population of pregnant women was screened for gdm between 1995 and 2006 . although the proportion of women with ifg on their postpartum screen did not significantly change over time , the proportion of women with diabetes ( diagnosed by fpg levels ) at postpartum decreased by 50% . this observed decrease in diabetes among women with postpartum screening is not likely to be a consequence of the small increase ( 3% ) in gdm screening over time . the decrease is more likely because of better identification of diabetes before pregnancy , as suggested by the reported increase in postpartum screening among women with gdm and because of an increase in glucose screening in postpartum women without gdm ( 1.9% in 1995 vs. 8.2% in 2006 ) . as in other reports ( 58 ) , the majority of women in our cohort did not undergo postpartum diabetes screening in the early years of the study . it is possible that health care providers might have recommended more postpartum screening among these racial / ethnic groups , given their higher prevalence of diabetes ( 19 ) . it is also possible that asian women were more likely to have had a recent physical examination , giving the health care provider the opportunity to recommend screening , as suggested by racial / ethnic differences in access to care among gdm women ( 20 ) . similar to other reports , we found that greater contact with medical care , either through a postpartum visit or other contacts , was associated with greater postpartum screening and may have provided additional opportunities to perform screening ( 6,7 ) . women who were more likely to be screened also were older and had higher educational attainment . although reasons are speculative , these women may have had greater awareness of their diabetes risk and the recommendation for screening . in women who were screened postpartum , gdm was diagnosed earlier in their index pregnancy , and they were more likely to have been treated with medications , which may have increased their and their provider 's awareness of their diabetes risk . glucose levels on the diagnostic 3-h ogtt during pregnancy were similar in women who were and were not screened , suggesting that these were not used to guide testing . as shown by others ( 21 ) , there was a suggestion that some of the women with a history of gdm who might have had a higher risk of developing diabetes during the postpartum period , such as those who were obese or with higher parity , were less likely to perform postpartum screening . the american diabetes association ( 16 ) , the american college of obstetricians and gynecologists ( 17 ) , and the fifth international congress workshop for gestational diabetes ( 15 ) endorse the postpartum ogtt and fpg to different extents . if only fpg were used in postpartum screening , 74 ( 40% ) cases of igt and 16 ( 75% ) cases of diabetes would have been missed . kitzmiller et al . ( 19 ) reported that among 527 women with gdm , at postpartum 16.5% had isolated igt , only 16% of women in whom diabetes was diagnosed met the criteria for both elevated fpg and 2-h values , and 21 of 25 women met the criteria for diabetes according to their 2-h values alone . hunt and conway ( 21 ) also reported that one - third of their postpartum gdm cohort undergoing the ogtt and who had diabetes or pre - diabetes had isolated 2-h elevations . their results are very similar to those found in this study : 78 of 204 women compared with 41 of 117 ( or 38% vs. 35% ) . therefore , the greater convenience of the fpg needs to be weighed carefully against its decreased sensitivity , particularly among women with a history of gdm . we were not able to distinguish whether the lack of screening occurred because of a lack of provider order or other reasons . however , provider orders for screening might occur only after negotiation with the patient , and a lack of provider order may , at least in part , reflect women 's objections to the test . we defined obesity by using race / ethnicity - specific percentiles , rather than height - to - weight ratios , thus introducing the possibility for misclassification and artificially decreasing the association between obesity and screening to the null . information on other confounders , such as family history of diabetes , was not available from electronic records . because the population of women with gdm is of reproductive age , postpartum screening and subsequent diagnoses of diabetes affect not only the mothers but also future pregnancies . the risk of complications , particularly stillbirths and congenital abnormalities , may be reduced with optimal glycemic control before the subsequent pregnancy ( 1 ) . prepregnancy glycemic control might also reduce the risk of the infant to the in utero exposure to hyperglycemia that might lead to childhood obesity and diabetes ( 22 ) . a diagnosis of pre - diabetes would identify women at high risk of future maternal diabetes , but this risk could be reduced through the application of interventions such as thiazolidinediones , metformin , or intensive lifestyle modification ( 3,4 ) . we conclude that , among women with a gdm history , postpartum diabetes screening has increased , but screening is still suboptimal . performance of an fpg alone , as opposed to the ogtt , will miss a subpopulation of women at risk .
objective  the purpose of this study was to examine trends in postpartum glucose screening for women with gestational diabetes mellitus ( gdm ) , predictors of screening , trends in postpartum impaired fasting glucose ( ifg ) and diabetes , and diabetes and pre - diabetes detected by postpartum fasting plasma glucose ( fpg ) versus a 75-g oral glucose tolerance test ( ogtt).research design and methods  this was a cohort study of 14,448 gdm pregnancies delivered between 1995 and 2006 . 
 postpartum screening was defined as performance of either an fpg or ogtt at least 6 weeks after delivery and within 1 year of delivery.resultsbetween 1995 and 2006 , the age- and race / ethnicity - adjusted proportion of women who were screened postpartum rose from 20.7% ( 95% ci 17.823.5 ) to 53.8% ( 51.356.3 ) . 
 older age , asian or hispanic race / ethnicity , higher education , earlier gdm diagnosis , use of diabetes medications during pregnancy , and more provider contacts after delivery were independent predictors of postpartum screening . obesity and higher parity 
 were independently associated with lower screening performance . among women who had postpartum screening , 
 the age- and race / ethnicity - adjusted proportion of ifg did not change over time ( 24.2 [ 95% ci 20.027.8 ] in 19951997 to 24.3 [ 22.626.0 ] in 20042006 ) , but the proportion of women with diabetes decreased from 6.1 ( 95% ci 4.28.1 ) in 19951997 to 3.3 ( 2.64.0 ) in 20042006 . among women who received an ogtt in 2006 , 
 38% of the 204 women with either diabetes or pre - diabetes were identified only by the 2-h glucose measurements.conclusionspostpartum screening has increased over the last decade , but it is still suboptimal . 
 compared with fpgs alone , the 2-h values identify a higher proportion of women with diabetes or pre - diabetes amenable to intervention .