The influence of maternal weight, smoking, vascular complications and glucose regulation on the birth weight of infants of type 1 diabetic women

The influence of maternal blood glucose regulation, weight gain, pre-pregnancy weight, vascular complications and smoking on the birth weight of infants was investigated in 72 type 1 (insulin-dependent) pregnant diabetic women. In patients with vascular complications (n = 23) the birth weight was significantly lower than in patients without vascular involvement (n = 49) (mean 380 g, P less than 0.05). The mean RBWR (relative birth weight ratio) of infants of patients who smoked more than 10 cigarettes per day was statistically significant lower compared to the mean RBWR of infants of non-smokers (P less than 0.025). A significant correlation was present between haemoglobin A1c (HbA1c) and RBWR (r = 0.28, P less than 0.02) and between maternal net weight gain and RBWR (r = 0.36, P less than 0.005) and this correlation became even stronger when only patients without vascular lesions were considered (n = 49) (r = 0.51, P less than 0.005) and (r = 0.50, P less than 0.005), respectively. In contrast no correlation was found between pre-pregnancy weight and RBWR. The study suggests that factors other than maternal hyperglycaemia stimulate fetal growth and may explain why fetal macrosomia may occur despite of strict blood glucose regulation.