A Matter of Time: Does Gestational Age Affect the Duration of the Fetal Anatomic Survey?

To assess the average duration of detailed fetal anatomic surveys in pregnancy in relation to gestational age (GA) and the maternal body mass index (BMI) to determine optimal timing of the examination.

This was a retrospective cohort study of gravidae presenting for detailed fetal anatomic examinations between January 1, 2010, and June 30, 2017. After excluding examinations expected to have longer duration (ie, multifetal, major fetal anomalies), there were a total of 6522 examinations performed between GAs of 18 weeks 0 days and 22 weeks 0 days. Women were grouped by BMI, and results were analyzed by logistic regression.

Gravidae of normal weight (BMI, 18.5-24.9 kg/m² ) had a decrease of 47.47 seconds of the examination time with each increasing week of gestation (P = .036). Overweight (BMI, 25-29.9 kg/m² ) gravidae similarly had a decrease of 66.31 seconds of the examination time with each additional week of gestation (P = .017). Underweight (BMI, 8.5 kg/m² ) and obese (BMI, ≥30 kg/m² ) gravidae did not have differences in the examination time with increasing GA. Increases in suboptimal examinations were noted with an increasing BMI (P < .001). There was a decreased frequency of suboptimal examinations in obese gravidae with a BMI of 40 kg/m² or higher with increasing GA (P = .037).

The duration of detailed fetal anatomic examinations decreased with increasing GA in normal-weight and overweight gravidae but not in obese gravidae. Performing the anatomy scan earlier in class I and II obese gravidae (BMI, 30-40 kg/m² ) may enable improved pregnancy management options without increasing the examination duration or likelihood of a suboptimal evaluation.