1090: Identification of macrosomic newborns: One versus two-step approach

Abstract

Limitations of Hadlock’s equations in identifying macrosomic fetuses (birthweight [BW] ≥ 4000g or ≥ 4500g) are known. Our objective was to evaluate a two-step screening method for detection of macrosomia utilizing Hadlock I to preselect at-risk women prior to application of a second regression equation. We performed a multicenter, retrospective review of all non-anomalous singletons who had ultrasound, by RDMS, within two weeks of delivery between 2013-2019. Our study group included all women with a Hadlock I calculated sonographic estimated fetal weight (SEFW) ≥ 4000g; additionally, to account for true and false negatives, we added an equal number of women with SEFW 3500-3999g. We then applied one of 43 published fetal weight regression equations to establish the “second step” SEFW. Area under the receiver operator curve (AUC), detection rate (DR), false positive rate (FPR), and accuracy (ACC) were calculated for all equations using our two-step method, and for Hadlock I alone, for detection of BW ≥ 4000g and 4500g. A paired analysis was performed to evaluate performance of each equation in the two-step approach versus Hadlock I as the reference. Of the 615 women who met inclusion criteria, 247 (40.2%) had BW ≥ 4000g and 56 (9.1%) had BW ≥ 4500g. There was no significant improvement for detection of BW ≥ 4000g with a two-step method compared to Hadlock I alone; however, the FPR was significantly decreased for detection of BW ≥ 4500g by applying equations by Ott or Hammami without a significant change in the detection rate (Table 1). Hadlock I remains relevant in a contemporary population for detection of BW ≥ 4000g. To identify newborns with BW ≥ 4500g, a two-step approach utilizing Hadlock I followed by Ott or Hammani significantly decreases the FPR, without compromising detection rate, and may be useful in clinical practice.