Macrosomia in Infants of Insulin-Dependent Diabetic Mothers

Abstract

The purpose of the present study was to evaluate factors affecting the rate of macrosomia and related complications in a population of infants of insulin-dependent diabetic mothers. The following factors were hypothesized to be predisposing to macrosomia: increased maternal weight gain during gestation, increased number of births until infant No. 3, white race, increased maternal age, poor glycemic control from the 20th week of gestation, and increased insulin dose. Advance White classification and increased duration of diabetes were predicted to be inversely related. In addition, macrosomia was hypothesized to predispose to selected adverse perinatal outcomes including premature labor, birth asphyxia, birth injury, hypoglycemia, polycythemia, and respiratory distress syndrome. From 1978 to 1986, 127 pregnancies were prospectively studied, 86 of the total number of women were entered prior to 10 weeks' gestation, and 41 were entered after 10 weeks' gestation. Patients monitored blood glucose at least twice daily with glycemic control achieved by "split-dosage" regimens of insulin. Glycohemoglobin was measured monthly. Pregnancy dating was based on the date of the last menstrual period and the Ballard score of the infant at birth. Macrosomia was defined as a birth weight greater than the 90th percentile of the intrauterine growth curves of Lubchenco. Of the babies born to mothers with insulin-dependent diabetes, 43% were large for gestational age and 57% were appropriate for gestational age. Maternal factors predisposing to an infant being large for gestational age included glycohemoglobin measurement at the time of delivery (large for gestational age = 8.4% ± 0.3%, appropriate for gestational age = 7.6% ± 0.2%, P < .05, normal = 5.5% to 8.5%), reflecting poorer glycemic control during the third trimester, weight gain in the third trimester, and advanced White classification by univariate analysis compared to mothers of babies with birth weights appropriate for gestational age. However, only glycohemoglobin at the time of delivery was significant when these variables were subjected to multiple logistical regression. Macrosomic infants had higher rates of both polycythemia (large for gestational age = 23.6%, appropriate for gestational age = 6.9%, P < .008) and hyperbilirubinemia (large for gestational age = 29.6%, appropriate for gestational age = 12.7%, P < .02) than nonmacrosomic infants but did not differ in other perinatal outcomes. The data suggest that, in spite of improvements in glycemic control in the recent past, macrosomia still exists at an increased rate in infants of diabetic mothers and is significantly related to poorer glycemic control in the third trimester. In addition, large for gestational age infants are at an increased risk for both polycythemia and hyperbilirubinemia.