LAUSR

365 Accuracy of clinical estimation of fetal weight: does maternal height matters? Reut Mazuz, Oren Barak, Yoav Brezinov, Roni Levy, Alon Ben-Arie, Edi Vaisbuch Kaplan medical center, Rehovot, Rehovot, Israel OBJECTIVE: Clinical estimation of fetal weight (EFW) prior to delivery is a routine obstetric practice. The effect of maternal height on the accuracy of EFW is unclear. The aim of this study was to examine the accuracy of clinical EFW according to maternal height. STUDY DESIGN: This retrospective cohort study included women with singleton pregnancies at term ( 37 weeks) who delivered in our institution between January 2015 and June 2018 and for whom maternal height, pre-pregnancy and current weight and clinical EFW were recorded before delivery. We assessed the magnitude of clinical EFW error according to maternal height. An absolute error was calculated as follow: [(actual birthweightclinical EFW)/actual birthweight]x100. An underor over-estimation of FW were defined as errors of 10% below or above the actual birthweight, respectively. The absolute error and the distribution of accurate (-10% to +10%) underand overestimation of FW were compared across maternal height percentiles [<10, 10-90, >90] and BMI (kg/ m2) categories (<18.5, 18.5-24.9, 25-29.9, >30). RESULTS: A total of 12,902 women met the inclusion criteria. The 10 and 90 height centiles of this cohort were 155cm and 170cm, respectively. The rate of accurate, underand over-estimation of FW in the total cohort were 70.5%, 18% and 11.6%, respectively. The distributions across maternal height centile and BMI categories are presented in Table 1 .Among women in the >90 height centile, the rate of under-estimation was higher than the rate of over-estimation (23.6% vs. 6.7%, p<0.001) while among women in the <10 height percentile the opposite was notices (under-estimation 13.9% vs. over-estimation 19.2%, p<0.001). The CS rate of the entire cohort was 16.3%. Interestingly, although the CS rate was significantly higher in the over-estimation compared to the under-estimation group (24.5% vs. 12.5%, p<0.001), the mean birthweight was significantly lower in the overcompared to the underestimation group (2830 gr vs 3772 gr, p<0.001). CONCLUSION: At the extremes of maternal heights percentiles, clinical EFW is more challenging, with a higher rate of underestimation in tall women and a higher rate of over-estimation in short women.Over-estimtion of FW has a negative impact on the CS rate.This limitation of clinical EFW at the extremes of the maternal heights should be acknowledge and in these women additional tools (i.e., sonographic EFW) should be considered for clinical making decisions before delivery.