Maternal Prepartum Intravenous Fluid Administration is associated with Neonatal Weight Loss at day 2 of life

Purpose Maternal intravenous fluid administration during labor is widely used for treatment administration and to ensure adequate uteroplacental perfusion. Its potential effects on neonatal outcomes, particularly early weight loss, are not fully understood, with data mainly derived from breastfed infants. Evidence in formula-fed infants remains lacking. We aimed to evaluate the impact of prepartum maternal fluid administration on 48-hour weight loss in exclusively formula-fed newborns. Blood cord haematocrit was also studied as a reflect of neonatal potential blood dilution. Methods This retrospective, observational study was conducted at Amiens-Picardie University Hospital between September and December 2024. Term singleton infants exclusively formula-fed during the first two days of life were included. Maternal intravenous fluid volumes during the 12 hours preceding delivery were recorded. Primary outcome was neonatal weight loss at day 2. The secondary outcome was blood cord hematocrit. Results Among 200 mother-infant dyads, maternal fluid loading > 4 mL/kg in the 4–6 hours before delivery was significantly associated with greater neonatal weight loss at 48 hours (p = 0.0168 and p = 0.027, respectively). Oxytocin exposure was also associated with an increased weight loss (p = 0.036). Higher fluid intake > 2 mL/kg in the 2 hours before delivery correlated with lower cord haematocrit (p = 0.024). Conclusion A higher maternal intrapartum fluid administration was associated with an increased neonatal weight loss and a lower blood cord hematocrit in formula-fed infants. These findings support the hypothesis of transient neonatal fluid overload followed by diuresis, and underline the need to account for maternal fluid balance when interpreting early neonatal weight changes.