https://orcid.org/0000-0002-1686-5303
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Abstract
Objectives
The aim of this study is to determine if the gestation adjusted projection (GAP) method applied to a fetal head circumference (FHC) measured on ultrasound between 32 and 36 weeks and 6 days gestation can predict birth head circumference, specifically ≥ 35 cm, which is a known risk factor for Cesarean.
Methods
This is a retrospective chart review of 60 pregnancies from January to December 2019. Eligible patients delivered a singleton term neonate and received two ultrasounds, one at 32–36 weeks and 6 days gestation (period 1) and a second within 7 days of a term birth (period 2). Fetal head circumference was predicted two ways, by applying (1) the GAP method to the period 1 ultrasound and (2) by direct measurement with a period 2 ultrasound. These estimates were compared to the birth head circumference (HCBIRTH) by measures of error and with paired t-tests. McNemar’s test compared the ability to predict head circumference (HC) ≥ 35 cm.
Results
None of the measures of error were significantly different between the GAP and the period 2 ultrasound, including the ability to predict HC ≥ 35 cm. In patients who delivered at ≥ 39 weeks, the period 2 ultrasound performed poorly while the GAP’s performance remained good.
Conclusion
The GAP method applied to an early third trimester ultrasound predicts HCBIRTH with accuracy similar to an ultrasound performed seven days from delivery and may be superior for deliveries ≥ 39 weeks. The ability to predict HCBIRTH could improve clinical management of affected pregnancies.
Disclosure statement
There are no conflicts of interest for any of the authors. There was no funding or grants for this research project. Presentation Information: 41st Annual Society of Maternal Fetal Medicine Meeting, Virtual, 25–30 January 2021 with poster presentation, abstract #654, on 29 January 2021.