Background and Objective:
Inadequate gestational weight gain (GWG) affects maternal-child health. Similarly, sex differences – early evident before birth – influence the risk of adverse outcomes. The present analysis aims to evaluate the effect of GWG on delivery and neonatal characteristics, focusing on the potential role of sex in this relationship.

Methods:
We used data from the ongoing “MAMI-MED” birth cohort settled in Catania (Italy). Adequate GWG was defined according to pre-gestational body mass index: 12.5–18 Kg (underweight), 11.5–16 (normal weight), 7–11.5 (overweight), and 5–9 (obese). Information about gestational age at delivery, birth length and weight, and birthweight for gestational age were collected. The latter was defined as small (SGA), adequate (AGA) or large for gestational age (LGA) according to sex-specific national reference charts.

Results:
The study included 687 mother-child dyads (median maternal age = 31 years), with a median gestational age at delivery of 39 weeks. Among newborns (49.4% males), 81.1% were AGA, 7.5% SGA, and 11.3% LGA. The proportion of SGA was higher in males than in females (69.2% and 30.8% respectively; p = 0.007). Accordingly, the risk of SGA was almost 2.5 times greater in males (OR= 2.470; 95% CI = 1.28 – 4.75; p = 0.007). Regarding maternal characteristics, 65.8% mothers reported inadequate GWG (37.6% and 28.2% with reduced or excessive GWG). Birth weight was lower in infants born from mothers with reduced GWG (p=0.006). After sex stratification, the relationship was confirmed in males (p=0.009) and females (p=0.013). There were also differences in gestational age according to GWG (p=0.019), although this finding was confirmed only in the male sex (p = 0.025).

Conclusion:
Our findings confirmed how GWG may affect delivery and neonatal characteristics, also pointing out possible differences by sex. Further research is needed to deeply understand sex differences and mechanisms underlying pregnancy complications.