Are birth weight predictors in diabetic pregnancy the same in boys and girls?

Objectives: To study the predictors of abnormal fetal growth in diabetic pregnancy, analyzing the role of fetal sex.

Study design: Observational retrospective study was carried out in a University hospital. We studied 2833 newborns of diabetic mothers who attended the Diabetes and Pregnancy Clinic and delivered in the center between 1/1/1982 and 31/12/2006 (2370 born to women with gestational diabetes mellitus, 391 to women with type 1 diabetes mellitus (DM), and 72 to women with type 2 DM). Logistic regression analyses were performed with a backward method to predict large for gestational age (LGA), small for gestational age (SGA) and macrosomic newborns using relevant variables and their interaction with fetal sex. We have used as potential predictors of abnormal birth weight: maternal prepregnancy age, weight, height and body mass index, prior pregnancy, prior macrosomia, smoking habit, weight increase during pregnancy, hypertension, gestational age at delivery, twin pregnancy, fetal sex, diabetes type, third trimester HbA1c and interaction of fetal sex with all these variables.

Results: Variables predictive of LGA, SGA and macrosomia were as formerly described. Moreover, some predictors of abnormal growth displayed an interaction with fetal sex. In LGA prediction, male sex displayed a positive interaction with delivery week, prior gestation, diabetes type and twin pregnancy and a negative one with weight increase. In SGA prediction, male sex displayed a positive interaction with delivery week and diabetes type. In macrosomia prediction, male sex displayed a negative interaction with weight increase.

Conclusions: In this cohort of diabetic pregnancies, some predictors of abnormal birth weight display interaction with fetal sex. In general, associations were more favorable to female fetuses.