Impact of Fetal Weight Estimation on the Prediction of Neonatal Morbidity and Mortality at the Limit of Viability.

INTRODUCTION: To determine the accuracy of estimated fetal weight (EFW) at the limit of viability in a delivery room setting and its impact on the prediction of neonatal outcome.

MATERIAL AND METHODS: In this retrospective, single-center cohort study we included patients with preterm birth between 230/7 and 260/7 weeks of gestation. Neonates were divided into 3 groups according to birth weight at delivery (accuracy index 90-110%, <90%, >110%). Neonatal outcome for each group was categorized into survival with and without impairment and death, with a follow-up period of 6 weeks.

RESULTS: Eighty-seven newborns were included, with 62.1% accurately estimated. Gestational age at birth, fetal sex, maternal body mass index, and time interval between birth and ultrasound affected the accuracy of EFW. Chances of survival were significantly higher in the underestimated group for birth weight at delivery compared with estimated weight (p < 0.001), with risk of death being significantly lower (p < 0.001). The reverse was true for overestimated infants, for both risk of death and chances of survival. At 6 weeks' follow-up, there were significantly more deceased overestimated infants (p = 0.041).

DISCUSSION: Our study shows that inaccuracy of EFW at the limit of viability occurs frequently in a delivery room setting with a potential impact on neonatal outcome.