Objective
The purpose of this study was to determine racial/ethnic differences in perinatal outcomes among women with gestational diabetes mellitus.
Study Design
We conducted a retrospective cohort study of 32,193 singleton births among women with gestational diabetes mellitus in California from 2006, using Vital Statistics Birth and Death Certificate and Patient Discharge Data. Data were divided by race/ethnicity: white, black, Hispanic, or Asian. Multivariable logistic regression was used to analyze associations between race/ethnicity and adverse outcomes that were controlled for potential confounders. Outcomes included primary cesarean delivery, preeclampsia, neonatal hypoglycemia, preterm delivery, macrosomia, fetal anomaly, and respiratory distress syndrome.
Results
Compared with women in other races, black women had higher odds of preeclampsia (adjusted odds ratio [aOR], 1.57; 95% confidence interval [CI], 1.47–1.95), neonatal hypoglycemia (aOR, 1.79; 95% CI, 1.07–3.00), and preterm delivery <37 weeks’ gestation (aOR, 1.56; 95% CI, 1.33–1.83). Asian women had the lowest odds of primary cesarean delivery (aOR, 0.75; 95% CI, 0.69–0.82), large-for-gestational-age infants (aOR, 0.40; 95% CI, 0.33–0.48), and neonatal respiratory distress syndrome (aOR, 0.54; 95% CI, 0.40–0.73).
Conclusion
Perinatal outcomes among women with gestational diabetes mellitus differ by race/ethnicity and may be attributed to inherent sociocultural differences that may impact glycemic control, the development of chronic comorbidities, genetic variability, and variation in access to prenatal care, and quantity and quality of prenatal care.
Gestational diabetes mellitus (GDM) is defined as glucose intolerance with onset or first recognition during pregnancy. GDM affects approximately 7-14% of all pregnant women and is associated with multiple obstetric and neonatal complications, which includes cesarean delivery (CD), preeclampsia, preterm delivery (PTD), fetal macrosomia, shoulder dystocia, neonatal jaundice, and neonatal hypoglycemia. The incidence of GDM has increased dramatically in the past decade in all racial/ethnic groups. Studies of the racial/ethnic distribution of GDM have shown significant variation in its prevalence. Studies have found higher rates of GDM among Asian, Hispanic, Native American, and African American women, compared with non-Hispanic white women. Asian women, with a reported rate as high as 15%, are more likely to have GDM than any other race, particularly when the data are controlled for body mass index and socioeconomic status. Variations in the distribution of GDM by race/ethnicity may be related to genetic factors that affect insulin resistance, diet, lifestyle, sociocultural factors, healthcare access/use, or even provider discrimination. Because maternal hyperglycemia is associated with increased birthweight and insulin levels in the offspring, lifestyle modifications or medical treatment may lower the risk of adverse perinatal outcomes.
Yet under the same treatment regimens, significant disparities persist in the analysis of adverse perinatal outcomes by race and ethnicity. Given that Hispanic women are projected to be California’s racial/ethnic majority within the next 3 decades, research and subsequent clinical recommendations should be culturally sensitive and appropriately tailored to their risk. Understanding racial/ethnic differences in GDM diagnosis, management, and outcomes is thus an important step towards the resolution of disparity and widespread improvement of maternal and child health.
A recent study of GDM compared outcomes among the most common racial/ethnic groups in the United States (white, black, Latina/Hispanic, Asian). After data were controlled for maternal age, parity, obesity, gestational age (GA) at delivery, weight gain during pregnancy, maternal education, and primary language, the findings confirmed an increased risk of primary CD, PTD, and fetal death in black women compared with other groups. GDM was still most common, however, among Asian and Latinas/Hispanic women. Unfortunately, this study was not detailed enough to capture many of the neonatal complications that are associated with GDM, such as shoulder dystocia, neonatal jaundice, respiratory distress, and neonatal hypoglycemia and examined only neonatal intensive care unit admission rates. Neonatal complications that are associated with maternal hyperglycemia are important factors for both patient and provider for counseling and decision-making, because infants who are born with neonatal hypoglycemia are up to 3.5 times more likely to have neurodevelopmental impairment at ≤5 years of age. Given this background, we sought to study perinatal outcomes among women with GDM. Specifically, we compared a broad range of maternal and neonatal outcomes by race/ethnicity.
Materials and Methods
This was a retrospective cohort study of 32,193 singleton births among women with GDM in California from 2006 whose information could be found in the Vital Statistics Birth and Death Certificate files that are linked with California Patient Discharge Data. Institutional Review Board approval was obtained from the University of California, San Francisco, Oregon Health & Science University, and the State of California. Because the linked dataset did not contain patient privacy and identification information, informed consent was exempted.
Inclusion criteria included women with singleton pregnancies who delivered in California. Diagnosis of GDM was obtained through a review of International Classification of Diseases–9 codes from hospital discharge data. Patients with pre-GDM (type 1 or 2) were excluded.
Outcomes that were analyzed were those that were associated with increased maternal or neonatal morbidity and the use of hospital resources, which included preeclampsia, primary CD, PTD at <37 weeks’ gestation, PTD at <32 weeks’ gestation, small for gestational age, large for gestational age, macrosomia, intrauterine fetal death, fetal anomaly, neonatal hypoglycemia, neonatal jaundice, and respiratory distress. Some of these outcomes are defined specifically with little expected variation in diagnosis, such as PTD at <37 or <32 weeks’ gestation or macrosomia as birthweight of <4000 g. However, other outcomes are designated by the clinicians who care for the parturients or their neonates. Neonatal jaundice is variably defined by a total bilirubin level in the 95th percentile (13-18 mg/dL). Similarly, practitioners may adopt varying thresholds for the diagnosis and treatment of neonatal hypoglycemia, which ranges from 36–50 mg/dL. Shoulder dystocia is a subjective clinical diagnosis that is made when the routine practice of gentle, downward traction of the fetal head fails to deliver the anterior shoulder. Often underreported, it has been described as the need for ancillary maneuvers to deliver the shoulder and/or a head-to-body delivery time >60 seconds.
Demographic information and maternal characteristics (such as parity, history of CD, and gestational age at delivery) were obtained from either birth certificate entries or hospital discharge information. Maternal race/ethnicity was self-reported by patients and categorized into 4 groups: white, black, Hispanic/Latina, and Asian.
Outcomes were coded and entered into STATA software (version 10; StataCorp, College Station, TX). Multiple variables were collapsed from continuous or categoric into binary variables and included age (>35 years) and education (college attendance). Chi-squared tests were used to compare dichotomous outcomes. Statistical significance was indicated by a probability value < .05. Multivariable logistic regression analyses were then performed to determine associations between race/ethnicity and perinatal outcome, when controlled for the following potential covariates: advanced maternal age, college education, initiation of prenatal care in the first trimester, prepregnancy obesity, parity, gestational age at delivery, and chronic hypertension. The results were reported as adjusted odds ratios with 95% confidence intervals.
Results
Of the 516,837 women who delivered within the reviewed timeframe (2006), 6.2% women (n = 32,193) received a diagnosis of GDM and had sufficient records for inclusion in the data analysis. The largest proportion was Hispanic (47.9%), as compared with white (34.6%), black (5.5%), and Asian (12.0%). The unadjusted prevalence of GDM by race/ethnicity, however, showed a greater proportion of Asian women with GDM (10.0%), compared with white (4.6%), black (4.5%), and Hispanic (6.9%) women. Maternal characteristics that were separated by race are shown in Table 1 . The proportion of women with maternal age ≥35 years at the time of delivery was higher in both white and Asian women (35.8-38.0%) than in black and Hispanics women (approximately 29.5%; P < .01). The Hispanic women with less than a college education comprised the highest proportion at 76.2%, compared with, at most, 41.2% in other groups. Obesity was more prevalent among black women (11.5%), compared with white (5.1%), Hispanic (4.8%), and Asian women (1.2%). Nulliparity was most common among Hispanic women (76.1%). Chronic hypertension was present in 3.5% of the sample population; however, black women made up the greatest proportion of this group (11.6%; P < .01). All groups had an average gestational age at delivery of at least 38 weeks ( Table 1 ).
| Maternal characteristic | Race/ethnicity | P value | |||
|---|---|---|---|---|---|
| White | Black | Hispanic | Asian | ||
| Advanced age: ≥35 y, n (%) | 2736 (35.9) | 360 (29.8) | 4916 (29.5) | 2237 (38.0) | < .01 |
| Education: at least some college, n (%) | 5021 (65.8) | 709 (58.7) | 3967 (23.8) | 4678 (79.5) | < .01 |
| Prenatal care before the second trimester, n (%) | 6882 (90.4) | 1040 (86.6) | 14,309 (86.1) | 5311 (90.5) | < .01 |
| Use of public health insurance, n (%) | 2069 (27.1) | 602 (49.9) | 10,856 (65.1) | 1045 (17.8) | < .01 |
| Obesity, n (%) | 386 (5.1) | 139 (11.5) | 801 (4.8) | 71 (1.2) | < .01 |
| Nulliparity, n (%) | 4748 (62.3) | 792 (65.7) | 12,672 (76.1) | 3355 (57.1) | < .01 |
| Chronic hypertension, n (%) | 318 (4.2) | 140 (11.6) | 499 (3.0) | 185 (3.1) | < .01 |
| Gestational age at delivery, wk a | 38.62 ± 2.31 | 38.12 ± 2.95 | 38.58 ± 2.23 | 38.51 ± 2.18 | < .01 |
Table 2 gives data on peripartum adverse outcomes that have been stratified by race/ethnicity. Black women had the highest proportion of preeclampsia (11.6% vs 4.1-6.0%), primary cesarean delivery (29.3% vs 20.7-26.0%), PTD <37 weeks’ gestation (19.4% vs 11.4-16.1%), and PTD at <32 weeks’ gestation (2.8% vs 1.0-1.1%; Table 2 ) compared with the other racial/ethnic groups. Shoulder dystocia was most prevalent among black and Hispanic women at 1.9-2.1%, compared with Asian women at 1.5% ( Table 2 ).
| Peripartum adverse outcome | Maternal race/ethnicity, n (%) | P value | |||
|---|---|---|---|---|---|
| White | Black | Hispanic | Asian | ||
| Preeclampsia | 409 (5.4) | 140 (11.6) | 1003 (6.0) | 242 (4.1) | < .01 |
| Primary cesarean section delivery | 1985 (26.0) | 354 (29.3) | 3454 (20.7) | 1325 (22.5) | < .01 |
| Preterm delivery, wk | |||||
| <37 | 916 (12.1) | 233 (19.4) | 2182 (13.2) | 672 (11.4) | < .01 |
| <32 | 80 (1.1) | 34 (2.8) | 192 (1.2) | 64 (1.1) | < .01 |
| Shoulder dystocia | 136 (1.8) | 23 (1.9) | 348 (2.1) | 86 (1.5) | .02 |
With respect to fetal/neonatal outcomes, black women again exhibited higher proportions of neonatal hypoglycemia (1.7% vs 0.5-0.8%), respiratory distress syndrome (3.5% vs 1.4-2.1%), and fetal anomalies (12.1% vs 7.2-8.2%; all P < .01; Table 3 ). Asian women had the highest proportion of small-for-gestational-age infants (14.0% vs 7.5-12.4%) and the accordingly lowest proportion of large-for-gestational-age infants (2.7% vs 5.4-6.6%; both P < .01; Table 3 ) compared with other groups. The proportion of women with intrauterine fetal death did not differ significantly between groups.
| Fetal/neonatal adverse outcome | Maternal race/ethnicity, n (%) | P value | |||
|---|---|---|---|---|---|
| White | Black | Hispanic | Asian | ||
| Neonatal hypoglycemia | 61 (0.8) | 20 (1.7) | 101 (0.6) | 29 (0.5) | < .01 |
| Small for gestational age | 503 (7.5) | 122 (12.4) | 1240 (8.5) | 735 (14.0) | < .01 |
| Macrosomia (birthweight, >4000 g) | 1151 (15.1) | 164 (13.6) | 2546 (15.3) | 355 (6.0) | < .01 |
| Large for gestational age | 504 (6.6) | 65 (5.4) | 972 (5.8) | 159 (2.7) | < .01 |
| Neonatal jaundice | 1638 (21.5) | 246 (20.4) | 3330 (20.0) | 1727 (29.3) | < .01 |
| Respiratory distress syndrome | 161 (2.1) | 42 (3.5) | 282 (1.7) | 80 (1.4) | < .01 |
| Intrauterine fetal death | 14 (0.2) | 3 (0.3) | 50 (0.3) | 14 (0.2) | .41 |
| Fetal anomalies | 552 (7.2) | 146 (12.1) | 1365 (8.2) | 485 (8.2) | < .01 |
Multivariable logistic regression analysis controlled for potential confounders (advanced maternal age, college education, early prenatal care, prepregnancy obesity, parity, chronic hypertension, and gestational age at delivery) that affected associations of race/ethnicity with GDM-related peripartum outcomes ( Table 4 ). White race was the designated reference group. The association of black race with greater GDM-related peripartum morbidity remained after logistic regression. Black race was associated with 1.6 times the risk of preeclampsia and PTD at <37 weeks’ gestation, compared with white women (adjusted odds ratio, 1.57 and 1.56; 95% confidence interval, 1.47–1.95 and 1.33–1.83 respectively). No other race was associated significantly with PTD. Asian women were significantly less likely than both black and white women to undergo primary CD ( Table 4 ).
| Adverse outcome | Maternal race b | ||
|---|---|---|---|
| Black | Hispanic | Asian | |
| Peripartum | |||
| Preeclampsia | 1.57 (1.47–1.95) | 1.18 (1.04–1.34) | 0.78 (0.66–0.93) |
| Primary cesarean delivery | 1.20 (1.04–1.39) | 0.93 (0.87–1.00) | 0.75 (0.69–0.82) |
| Repeat cesarean delivery | 0.74 (0.49–1.12) | 1.08 (0.87–1.34) | 0.73 (0.56–0.94) |
| Preterm delivery, wk | |||
| <37 | 1.56 (1.33–1.83) | 1.06 (0.97–1.15) | 0.94 (0.85–1.05) |
| <32 | 0.45 (0.30–0.68) | 0.96 (0.73–1.26) | 0.99 (0.71–1.36) |
| Shoulder dystocia | 1.07 (0.69–1.68) | 1.00 (0.81–1.23) | 0.84 (0.64–1.10) |
| Fetal | |||
| Neonatal hypoglycemia | 1.79 (1.07–3.00) | 0.69 (0.50–0.96) | 0.64 (0.41–1.00) |
| Small for gestational age c | 1.76 (1.42–2.17) | 1.22 (1.09–1.37) | 1.98 (1.76–2.23) |
| Large for gestational age c | 0.75 (0.57–0.97) | 0.84 (0.74–0.94) | 0.40 (0.33–0.48) |
| Macrosomia | 0.82 (0.69–0.98) | 0.90 (0.83–0.97) | 0.39 (0.34–0.44) |
| Neonatal jaundice | 0.80 (0.69–0.94) | 0.94 (0.88–1.01) | 1.47 (1.36–1.59) |
| Respiratory distress syndrome | 0.94 (0.63–1.39) | 0.69 (0.55–0.87) | 0.54 (0.40–0.73) |
| Intrauterine fetal death | 1.42 (0.29–7.05) | 1.99 (0.86–4.62) | 1.52 (0.53–4.43) |
| Fetal anomalies | 1.51 (1.24–1.84) | 1.11 (1.00–1.23) | 1.15 (1.02–1.31) |
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