Estimated fetal weight by ultrasound: a modifiable risk factor for cesarean delivery?
OBJECTIVE
The purpose of this study was to investigate whether knowledge of ultrasound-obtained estimated fetal weight (US-EFW) is a risk factor for cesarean delivery (CD).


METHODS
Retrospective cohort from a single center in 2009-2010 of singleton, term live births. CD rates were compared for women with and without US-EFW within 1 month of delivery and adjusted for potential confounders.


RESULTS
Of the 2329 women in our cohort, 50.2% had US-EFW within 1 month of delivery. CD was significantly more common for women with US-EFW (15.7% vs 10.2%; P < .001); after we controlled for confounders, US-EFW remained an independent risk factor for CD (odds ratio, 1.44; 95% confidence interval, 1.1-1.9). The risk increased when US-EFW was >3500 g (odds ratio, 1.8; 95% confidence interval, 1.3-2.7).


CONCLUSIONS
Knowledge of US-EFW, above and beyond the impact of fetal size itself, increases the risk of CD. Acquisition of US-EFW near term appears to be an independent and potentially modifiable risk factor for CD.
Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Brigham and Women's Hospital, Boston, MA, USA.
Sarah E
SE
Little
Andrea G
AG
Edlow
Ann M
AM
Thomas
Nicole A
NA
Smith
D001724:Birth Weight / Q000502:physiology*; D002585:Cesarean Section; D005260:Female; D020567:Fetal Weight / Q000502:physiology*; D005865:Gestational Age; D006801:Humans; D011237:Predictive Value of Tests; D011247:Pregnancy; D012189:Retrospective Studies; D012307:Risk Factors; D016216:Ultrasonography, Prenatal