Delay of Fetal Anatomy Ultrasound Assessment Based on Maternal Body Mass Index Does Not Reduce the Rate of Inadequate Visualization

Abstract

Objectives-To determine whether delay of initial anatomy ultrasound based on the maternal body mass index (BMI) reduces the rate of inadequate visualization compared to standard timing at 18 0/7 to 19 6/7 weeks. Methods-A retrospective study of singleton anatomy assessments was conducted at a tertiary care center in the 2-year period before (A, 2012-2014) and after (B, 2014-2016) protocol initiation. Assessments in period B were scheduled on the basis of the BMI in the first trimester: lower than 25 kg/m 2 , 18 0/7 to 19 6/7 weeks; 25 to 29.9 kg/m 2 , 19 0/7 to 20 6/7 weeks; 30 to 34.9 kg/m 2 , 20 0/7 to 21 6/7 weeks; 35 to 39.9 kg/m 2 , 21 0/7 to 22 6/7 weeks; and 40 kg/m 2 or higher, 22 0/7 to 23 6/7 weeks. In period A, assessments were scheduled between 18 0/7 and 19 6/7 weeks. The rate of inadequate visualization and repeated assessments in periods A and B were compared. Multivariable logistic regression, per-protocol, and BMI subgroup analyses were completed. Results-In total, 3491 pregnancies in period A and 3672 in period B were included. In period B, 74% were scheduled per protocol; however, this rate decreased for higher-BMI categories (52% for BMI ≥40 kg/m 2). The inadequate visualization rate was slightly higher in period B versus A (16.9% versus 15.0%; P = .03) and exceeded 35% for a BMI of 40 kg/m 2 or higher, with or without delay. After adjusting for maternal age and fetal presentation, period B had small increased odds of inadequate visualization versus period A (adjusted odds ratio, 1.2; 95% confidence interval, 1.02-1.38). Repeated assessment rates were similar in periods B and A (14.0% versus 13.1%; P = .25). Conclusions-In pregnancies with obesity, a protocol delaying the initial assessment beyond 19 6/7 weeks based on the maternal BMI does not reduce the rate of inadequate visualization.

Completion of Fetal Anatomy Evaluations in Women With Body Mass Index ≥ 50 kg/m2

“…In the 2000s and 2010s, there was significant literature showing that slightly later gestational age (eg, 22–24 weeks) impacts completion rate of the initial evaluation of anatomy in this population 21,22 . However, possibly related to improvements with imaging technology, this is now doubted by some, 23 and some advocate imaging in the first trimester or very early second trimester to aid completion of fetal anatomy 24,25 …”

“…In the 2000s and 2010s, there was significant literature showing that slightly later gestational age (eg, 22-24 weeks) impacts completion rate of the initial evaluation of anatomy in this population. 21,22 However, possibly related to improvements with imaging technology, this is now doubted by some, 23 and some advocate imaging in the first trimester or very early second trimester to aid completion of fetal anatomy. 24,25 Research Implications This study demonstrated the need for many follow-up ultrasounds in hundreds of patients; the impact of these additional imaging studies on cost of pregnancy care is not estimated in this study, nor is time spent scanning or impact on sonographers.…”