Objectives To evaluate the success of intrapartum external fetal monitoring in obese women.

Methods Group 1 (Liverpool Women's Hospital): A retrospective analysis of data for 400 labouring women with singleton pregnancies at ≥37+0 weeks gestation, stratified into four BMI groups (<30, 30–34.9, 35–39.9; ≥40). For each group we calculated the rate of suboptimal CTG recordings defined as the need for fetal scalp electrode (FSE).

Group 2 (Temple University Hospital Pennsylvania & Queens University Hospital New York)

19 obese women simultaneously monitored in labour with Doppler ultrasound (conventional external CTG), FSE (internal CTG – FSE) and a wireless external abdominal fetal (aECG) monitoring device (MONICA AN24).

Reliability was assessed with Positive Percent Agreement defined as the percentage of time when external fetal monitoring (aECG or CTG) gave an interpretable trace within 10% of the value reported by FSE.

Results Conventional external CTG monitoring in women with high BMI was associated with high percentage of labours requiring FSE monitoring (2% for BMI<30, 23% for BMI 30–34.9; 32% for BMI 35–39.9; and 45% for BMI >40).

When FSE recordings from 19 labouring women with BMI>35 were compared with simultaneously obtained aECG and external CTG recordings, the Positive Percent Agreement was 88.4% for aECG and 68.7% for the CTG.

Conclusion The external ECG monitoring with Monica AN24 may provide a useful alternative to Doppler CTG for women with high BMI.