No abstract

Background: Fetal weight estimation (FWE) is an important factor for clinical management decisions, especially in imminent preterm birth at the limit of viability between 23^0/7 and 26^0/7 weeks of gestation. It is crucial to detect and eliminate factors that have a negative impact on the accuracy of FWE. Data Sources: In this systematic literature review, we investigated 14 factors that may influence the accuracy of FWE, in particular in preterm neonates born at the limit of viability. Results: We found that gestational age, maternal body mass index, amniotic fluid index and ruptured membranes, presentation of the fetus, location of the placenta and the presence of multiple fetuses do not seem to have an impact on FWE accuracy. The influence of the examiner's grade of experience and that of fetal gender were discussed controversially. Fetal weight, time interval between estimation and delivery and the use of different formulas seem to have an evident effect on FWE accuracy. No results were obtained on the impact of active labor. Discussion: This review reveals that only few studies investigated factors possibly influencing the accuracy of FWE in preterm neonates at the limit of viability. Further research in this specific age group on potential confounding factors is needed.

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.