Estimated fetal weight by ultrasound: a modifiable risk factor for cesarean delivery?

Am J Obstet Gynecol. 2012 Oct;207(4):309.e1-6. doi: 10.1016/j.ajog.2012.06.065. Epub 2012 Jul 9.


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).

Study design: 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).

Conclusion: 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.

MeSH terms

  • Birth Weight / physiology*
  • Cesarean Section*
  • Female
  • Fetal Weight / physiology*
  • Gestational Age
  • Humans
  • Predictive Value of Tests
  • Pregnancy
  • Retrospective Studies
  • Risk Factors
  • Ultrasonography, Prenatal*