CONGENITAL-MALFORMATIONS IN OFFSPRING OF WOMEN WITH HYPERGLYCEMIA FIRST DETECTED DURING PREGNANCY

OBJECTIVES: Our aim was to determine risk factors for congenital malfo rmations in offspring of women with hyperglycemia first detected durin g pregnancy (i.e., women with gestational diabetes). STUDY DESIGN: A t otal of 3743 pregnancies complicated by gestational diabetes mellitus delivered at >20 weeks of gestation were reviewed for the presence of congenital malformations diagnosed before hospital discharge. Anomalie s were categorized as major, minor, or absent. Pregnancies with geneti c syndromes and aneuploidies were excluded. In addition to maternal cl inical and historic parameters, diagnostic glycemic parameters (lastin g and post-glucose-challenge levels from the diagnostic glucose tolera nce test, highest fasting serum glucose level, and hemoglobin A(1c) le vel before insulin therapy) were examined by logistic regression for p redictive risk of major anomalies. RESULTS: One or more major congenit al anomalies were present in 108 (2.9%) of the newborns; an additional 91 (2.4%) had only minor anomalies. None of the maternal variables we re associated with the risk of minor anomalies. By contrast, parity, a history of gestational diabetes mellitus, and several glycemic parame ters were associated with the risk of major anomalies. The highest fas ting serum glucose level was the best independent predictor (odds rati o 1.13/10 mg/dl, 95% confidence interval 1.09 to 1.34). The fasting se rum glucose level at diagnosis, a parameter that is almost uniformly a vailable to clinicians, gave similar predictive information about the risk of major anomalies (odds ratio 1.13, 95% confidence interval 1.08 to 1.14). Stratification of women into subgroups of fasting serum glu cose level at diagnosis revealed the incidence of major anomalies to b e as follows: 2.1% with a lasting serum glucose level <120 mg/dl (2973 pregnancies), 5.2% with a fasting serum glucose level of 121 to 260 m g/dl (747 pregnancies), and 30.4% with a fasting serum glucose level > 260 mg/dl (23 pregnancies). CONCLUSION: In a large population of women without a diagnosis of diabetes before pregnancy, the maternal fastin g serum glucose concentration at diagnosis was a useful predictor of t he risk of major but not minor anomalies. The rate of major anomalies doubled with a fasting glucose level >120 mg/dl. Thus a tasting glucos e level below that of overt diabetes outside of pregnancy carries an i mportant risk of major anomalies that must be considered in the counse ling and management of these patients.