Suboptimal second-trimester ultrasonographic visualization of the fetal heart in obese women: Should we repeat the examination?

Objective. The purpose of this study was to determine whether a repeated antenatal ultrasound examination improves fetal cardiac visualization for the obese and nonobese population. Methods. A computerized ultrasound database (October 1999-June 2003) was used to identify singleton pregnancies undergoing repeated prenatal ultrasound examinations because of initial suboptimal ultrasonographic visualization (SUV) of the 4-chamber view, outflow tracts, or both. Women with maternal diabetes, abnormal maternal serum screening results, or known fetal anomalies at the initial examination were excluded. Patients were classified by maternal body mass index (BMI): less than 30 kg/mg² (nonobese), 30 to 34.9 kg/mg² (class I obesity), 35 to 39.9 kg/mg² (class II obesity), and 40 kg/mg² or greater (morbid obesity). The association between maternal BMI and SUV of the fetal heart was analyzed. Results. Three hundred seventy-two patients were abstracted from the database. The median gestational age was 19.0 weeks at the initial visit (range, 18.0-21.9 weeks) and 21.4 weeks at the second visit (range, 18.9-23.9 weeks). The median BMI was 32.6 kg/m² (range, 16.4-58.7 kg/m²). Sixty-three percent of patients were obese (BMI ≥30). Cardiac anatomy continued to have SUV in 11% of the women. The rate of SUV was associated with the obesity class (1.5% for nonobese, 12% for obesity I, 17% for obesity II, and 20% for morbid obesity; P < .0001). A cardiac anomaly was found in 1 of 372 repeated examinations (arteriovenous canal defect) for a patient with BMI of 24.8 kg/m². Conclusions. Repeated ultrasound examination for SUV of the fetal heart at a later gestational age dramatically reduces SUV However, obese patients continue to have much higher rates of persistent SUV.