Pregnancy Complications and Perinatal Outcomes Among Women With Diabetes -- North Carolina, 1989-1990

Women with diabetes have a higher risk for complications of pregnancy than do women without diabetes; in addition, infants born to women with diabetes are at increased risk for adverse birth outcomes (1,2). Preconception counseling for women with established diabetes and early and continual prenatal care for women with established or gestational diabetes can reduce maternal and infant morbidity and mortality (3). Although the rate of pregnancy complicated by diabetes and the use of prenatal care varies by race of the mother (4), it is unknown whether the effect of diabetes on maternal and infant outcomes differs by race. Race reflects differing distributions of several risk factors for pregnancy outcomes (e.g., socioeconomic status and access to comprehensive health care) and is useful for identifying groups at greatest risk for adverse outcomes. To determine the prevalence of diabetes during pregnancy among women residing in North Carolina and to characterize differences in prenatal care and the risk for maternal complications and adverse pregnancy outcomes by race among mothers with diabetes, the North Carolina State Center for Health and Environmental Statistics examined birth certificates of infants of women who gave birth in the state during 1989-1990. This report summarizes the findings of the study.

For births occurring during 1989-1990, singleton live births to North Carolina residents were identified from computerized matched live birth and infant death records. Mothers with diabetes were identified by a check box for diabetes in the medical history section of the infant's birth certificate. The check box does not distinguish between established and gestational diabetes in pregnancy. For comparison, a computer-generated 7% random sample of live births with no mention of diabetes was selected. Birth certificates were reviewed to obtain information about maternal complications (i.e., polyhydramnios, pregnancy-induced hypertension, and pre eclampsia/eclampsia) and perinatal outcomes (i.e., macrosomia, birth injury, and hyaline membrane disease/respiratory distress syndrome) and maternal age, maternal race, and prenatal-care initiation. For infants who died before age 1 year, age at death was ascertained from the infant's death certificate. Logistic regression was used to determine odds ratios (ORs) and 95% confidence intervals (CIs) for the association between maternal diabetes, age, race, and selected pregnancy outcomes. An interaction term between maternal diabetes and race was included in the models to determine whether the relation between maternal diabetes and adverse events differed by race. For this analysis, maternal race was presented for blacks and other minority races combined * and for whites.

From January 1, 1989, through December 31, 1990, there were 201,823 singleton live births to North Carolina residents. Of these, 6092 (3%) women had a history of maternal diabetes (4451 white mothers and 1641 minority mothers). The prevalence of diabetes during pregnancy was 326.8 per 10,000 live births for white women and 251.7 per 10,000 live births for minority women. The prevalence increased with age of the mother for both racial groups. For women aged less than 30 years, pregnancies complicated by diabetes occurred 1.5 (Woolf 95% CI=1.4-1.6) times more often among white women than among minority women; for women aged greater than or equal to 30 years, pregnancies complicated by diabetes were 1.3 (Woolf 95% CI=1.1-1.4) times more likely in minority women.

Among women with pregnancies complicated by diabetes, 12.6% of white women and 24.7% of minority women initiated prenatal care during their second or third trimesters. Less than 1% of mothers reported with diabetes received no prenatal care. Among women with a pregnancy complicated by diabetes, those aged greater than or equal to 30 years were more likely to initiate prenatal care during their first trimester than were those aged less than 30 years (Table_1).

Compared with white women without diabetes, the risk for maternal complications was approximately two times greater among white mothers with diabetes and two to four times greater among minority mothers with diabetes (Table_2); however, differences in risks between white and minority women with diabetes were not statistically significant (0.40 less than p less than 0.75). When compared with infants born to white women without diabetes, infants of all women with diabetes were nearly twice as likely to experience a birth injury. The risk for infant mortality was greater in babies born to women with diabetes, especially after controlling for differences in birthweight. The risk for neonatal mortality varied significantly (p=0.04) by racial group. Congenital malformations accounted for 31.3% of the deaths among infants of mothers with diabetes. Reported by: RE Meyer, PhD, PA Buescher, PhD, State Center for Health and Environmental Statistics; K Ryan, MD, Div of Maternal and Child Health; North Carolina Dept of Environment, Health, and Natural Resources, Raleigh, North Carolina. Epidemiology and Statistics Br, Div of Diabetes Translation, National Center for Chronic Disease Prevention and Health Promotion, CDC.

Editorial Note

Editorial Note: Compared with corresponding race-specific groups in the United States, women in North Carolina have increased rates of pregnancy complicated by diabetes, regardless of age (4). Although North Carolina mothers with diabetes were more likely to initiate prenatal care during their first trimester than were all mothers in the United States in 1989 (4), approximately 12% of white mothers with diabetes and 25% of minority mothers with diabetes delayed initiation of prenatal care until their second or third trimesters, thereby increasing the risk for adverse pregnancy outcomes. The actual percentage of women with diabetes receiving late or no prenatal care is probably underestimated in this study because these women were less likely to have had their condition diagnosed during pregnancy.

Except for macrosomia, the magnitude of the effect of maternal diabetes on adverse maternal and infant outcomes in North Carolina was similar to that reported previously (2,3). The decreased risk for macrosomia in this report may reflect the exclusion of low-birthweight infants from the model.

In this study, the relation between socioeconomic status, adverse pregnancy outcomes, and race was not examined. Therefore, the extent to which the associations between race, maternal complications, and adverse infant outcomes reflect differences in distribution of socioeconomic status among the racial groups could not be determined. In addition, the findings in this report are subject to at least four limitations. First, pregnancies complicated by diabetes may have been underreported on birth certificates (5). However, the level of underreporting may be small because the overall prevalence of maternal diabetes was comparable to the prevalence of maternal diabetes obtained from all North Carolina hospital discharge summaries with Diagnosis Related Group (DRG) codes 370-375 (labor and delivery service charges) (6 ). Second, on North Carolina birth certificates, the types of diabetes (i.e., established or gestational) could not be differentiated. Therefore, calculated risks for adverse maternal or infant outcomes were probably underestimated among women with established diabetes and overestimated among women with gestational diabetes (particularly for perinatal mortality) (7). Third, differential recording of diabetes on the birth certificate by maternal and infant outcome status may have resulted in inflated risks for adverse outcomes among mothers with diabetes. Finally, because fetal deaths were not included in this analysis, the adverse impact of diabetes during pregnancy may have been underestimated (1).

Despite recent improvements in the diagnosis and management of diabetes, mothers with diabetes and their infants remain at increased risk for pregnancy complications and adverse outcomes. Many of these conditions may be prevented or successfully managed through preconception and risk-appropriate obstetric care (8). Women with diabetes should receive appropriate counseling from their physician regarding the risk for adverse pregnancy outcomes and the need to maintain strict metabolic control to increase the likelihood of a healthy pregnancy.

The findings in this report may assist the North Carolina Diabetes Control Program -- which integrates diabetes education into local public health delivery systems -- in targeting preconception and prenatal-care counseling toward those women with diabetes who are less likely to receive early prenatal care and who may be at higher risk for some adverse pregnancy outcomes (9,10). As part of a comprehensive program to reduce the burden of diabetes at both national and state levels, CDC recommends expanded state-specific surveillance for diabetes and its complications (including diabetes during pregnancy and adverse maternal and infant outcomes among mothers with diabetes) using data from the U.S. Standard Certificate of Live Birth. In addition, separate check boxes for established and gestational diabetes should be considered for incorporation into birth certificates.

References

1. Heckbert SR, Stephens CR, Daling JR. Diabetes in pregnancy: maternal and infant outcome. Pediatric and Perinatal Epidemiology 1988;2:314-26.

2. Jacobson JD, Cousins L. A population-based study of maternal and perinatal outcome in patients with gestational diabetes. Am J Obstet Gynecol 1989;161:981-6.

3. Schwartz R. The infant of the diabetic mother. In: Davidson JK, ed. Clinical diabetes mellitus. New York: Thieme Medical Publishers, 1991.

4. CDC. Prenatal care and pregnancies complicated by diabetes -- U.S. reporting areas, 1989. MMWR 1993;42:119-22.

5. Piper JM, Mitchel EF, Snowden M, Hall C, Adams M, Taylor P. Validation of 1989 Tennessee birth certificates using maternal and newborn hospital records. Am J Epidemiol 1993;137:758-68.

6. Meyer RE, Buescher PA, Sullivan LA. Diabetes in pregnancy in North Carolina. State Center for Health and Environmental Statistics, Raleigh, North Carolina, May 1992; CHES studies report no. 64.

7. Johnstone RD, Nasrat AA, Prescott RJ. The effect of established and gestational diabetes on pregnancy outcome. Br J Obstet Gynaecol 1990;97:1009-15.

8. American Diabetes Association. Standards of medical care for patients with diabetes mellitus. Diabetes Care 1989;12:365-8.

9. CDC. Public health guidelines for enhancing diabetes control through maternal- and child-health programs. MMWR 1986;35:201- 8,213.

10. Brown SS. Drawing women into prenatal care. Fam Plann Perspect 1989;21:73-80,88.

* Black (92.0%), American Indian/Alaskan Native (4.5%), Asian/Pacific Islander (3.4%), and other (0.1%). Estimates are not presented separately for minority races because numbers were too small for meaningful analysis.
Table_1
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TABLE 1. Percentage distribution of the initiation of prenatal care among mothers with
established or gestational diabetes, by age and race of mother -- North Carolina,
1989-1990
==================================================================================================
                                          White *                Black/Other minorities +
                              -----------------------------   -----------------------------
                                 <30 yrs>=30 yrs         <30 yrs>=30 yrs
Trimester of                  -------------   -------------   -------------   -------------
  prenatal-care initiation     No.    (%)      No.    (%)      No.    (%)      No.    (%)
-------------------------------------------------------------------------------------------
First                         2211  ( 84.8)   1669  ( 91.1)    686  ( 72.3)    541  ( 79.6)
Second                         337  ( 12.9)    152  (  8.3)    235  ( 24.8)    118  ( 17.3)
Third                           59  (  2.3)     12  (  0.6)     28  (  2.9)     21  (  3.1)

Total                         2607  (100.0)   1833  (100.0)    949  (100.0)    680  (100.0)
-------------------------------------------------------------------------------------------
* Excludes six with missing data and five with no prenatal care.
+ Black (92.0%), American Indian/Alaskan Native (4.5%), Asian/Pacific Islander (3.4%), and other
  (0.1%). Estimates are not presented separately for minority races because numbers were too
  small for meaningful analysis. Excludes five with missing data and seven with no prenatal
  care.
==================================================================================================

TABLE 2. Age-adjusted odds ratios (ORs) * and 95% confidence intervals (Cls) for
maternal complications and adverse outcomes of newborns among mothers with
established or gestational diabetes, by race -- North Carolina, 1989-1990
==============================================================================================
                                                                    Black/
                                             White             Other minorities +
                                        ----------------       ----------------
Characteristic                          OR     (95% CI)        OR     (95% CI)
-------------------------------------------------------------------------------
Maternal complications
  Polyhydramnios                        1.7    (1.1-2.6)       2.5    (1.5-4.2)
  Pregnancy induced hypertension        2.1    (1.8-2.4)       2.2    (1.7-2.7)
  Preeclampsia/Eclampsia                2.0    (1.3-3.2)       3.8    (2.3-6.3)

Adverse outcomes of newborns
  Macrosomia &                          1.2    (1.1-1.4)       1.1    (0.9-1.3)
  Birth injury                          1.9    (1.0-3.4)       1.7    (0.7-4.1)
  Hyaline membrane disease/
    Respiratory distress syndrome       1.4    (0.9-2.2)       1.2    (0.6-2.3)
  Infant deaths                         1.7    (1.1-2.6)       2.3    (1.4-3.9)
    Neonatal @                          1.7    (1.0-2.8)       2.2    (1.1-4.2)
    Postneonatal **                     1.7    (0.9-3.3)       2.6    (1.5-4.3)
-------------------------------------------------------------------------------
 * Referent: white women without diabetes.
 + Black (92.0%), American Indian/Alaskan Native (4.5%), Asian/Pacific Islander (3.4%), and
   other (0.1%). Estimates are not presented separately for minority races because numbers
   were too small for meaningful analysis.
 & Birthweight >=4000 g (>=8 lbs, 12 oz); p<0.05 for the interaction term between maternal
   diabetes and race.
 @ Age at death <28 days; infants with birthweight <2500g (<5 lbs, 8 oz) were excluded from
   the model; p<0.05 for the interaction term between maternal diabetes and race.
** Age at death >=28 days and <1 year.
==============================================================================================

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