Perinatal outcomes of small for gestational age neonates born to mothers with and without gestational diabetes mellitus

Objective
The perinatal outcomes of large for gestational age (LGA) neonates born to mothers with gestational diabetes mellitus (GDM) has been widely investigated however there is limited data regarding outcomes of small for gestational age (SGA) in this population. The objective of our study is to compare the perinatal outcomes of SGA neonates born to mothers with and without GDM.

Study Design
In a population-based retrospective cohort study, perinatal outcome of SGA newborns to mothers with and without GDM was evaluated. All SGA infants between the years 1991-2014 were included. Multiple pregnancies, patients lacking prenatal care, mothers with pre-gestational diabetes mellitus and neonates with congenital malformations or chromosomal abnormalities were excluded from the study. A multivariable generalized estimating equation (GEE) logistic regression model analysis was used to control for confounders and for maternal clusters.

Results
During the study period there were 9,333 deliveries of SGA neonates, of which 2.6% (n=236) occurred in patients with GDM. GDM mothers with SGA neonates were more likely to have hypertensive disorders during pregnancy (23.7% vs 8.7%, p<0.001), preterm birth (13.6% vs 5.3%, p<0.001) and cesarean deliveries (37.3% vs. 17.3%; p<0.001; Table). Perinatal mortality rate was significantly higher for SGA newborns to mothers with GDM as compared with SGA to mothers without GDM (1.7% vs. 0.5%; P=0.01). Using a GEE model, controlling for confounders such as hypertensive disorders in pregnancy, delivery of a SGA neonate to a GDM mother was noted as an independent risk factor for perinatal mortality (adjusted OR 2.8, 95% CI 1.1-7. 8, P=0.039).

Conclusion
Delivery of an SGA neonate to a diabetic mother is associated with a higher risk of perinatal mortality compared to a SGA neonate to a non-diabetic mother. Potential mechanisms need to be investigated further.