Standard External Doppler Fetal Heart Tracings versus External Fetal Electrocardiogram in Very Preterm Gestation: A Pilot Study.

 Very preterm babies can be difficult to monitor using standard external Doppler fetal heart tracings (eFHR). External fetal electrocardiogram (fECG) is a potential alternative.  This was a prospective observational pilot study of hospitalized patients at 24 to 28 weeks' gestation. A total of 30 women were traced for up to 2 hours using eFHR followed by up to 2 hours using fECG. The percentage of time the fetal heart rate was traced during the 2-hour window for each modality was calculated. Differences of ≥ 60, ≥ 80, and ≥ 90% total time traced were compared between modalities using McNemar's test. Differences were also assessed for each method between nonobese (body mass index [BMI] < 30 kg/m) and obese (BMI ≥ 30 kg/m) women using chi-square and Fisher's exact tests.  Superior performance was found with eFHR at ≥ 60% (93.3 vs. 46.7%,  < 0.001), ≥ 80% (80.0 vs. 30.0%,  < 0.001), and ≥ 90% (60.0 vs. 23.3%,  < 0.01) total time traced. There was a statistically significant finding favoring nonobese women at ≥ 80% total time traced using fECG (7.1 vs. 50.0%,  = 0.017).  With current technology fECG performance in very preterm gestation was worse than conventional eFHR, although fECG may have a role in nonobese patients.