Identification of Newborns with Birthweight ≥ 4,500g: Ultrasound within One- vs. Two Weeks of Delivery

Abstract Objective Our objective was to compare the diagnostic characteristics of sonographic estimated fetal weight (SEFW) done within 7 versus 8-14 days before delivery for detection of fetal macrosomia (birthweight ≥ 4,500 g). Study Design We performed a multicenter, retrospective cohort study of all non-anomalous singletons with SEFW ≥ 4,000 g by Registered Diagnostic Medical Sonographers conducted within 14 days of delivery. Cohorts were grouped by time interval between ultrasound and delivery: 0-7 days versus 8-14 days. The detection rate (DR) and false positive rate (FPR) for detection of birthweight (BW) ≥ 4,500 g were compared between groups with subgroup analysis for diabetic women. Area under the receiver operator curve (AUC) was calculated to analyze all possible SEFW cutoffs within our cohort. Results A total of 330 patients met inclusion criteria with 250 (75.8%) having SEFW within 7 days and 80 (24.2%) with SEFW 8-14 days prior to delivery. The rate of macrosomia was 15.1% (N = 51). The DR for macrosomia was significantly higher when SEFW was performed within 7 days of delivery compared to 8-14 days among non-diabetic (73.0% vs 7.1%; p  Conclusion With SEFW ≥ 4,000 g, the detection of BW ≥ 4,500 g is significantly higher when the sonographic examination is within 7 days of birth irrespective of maternal diabetes.