Comparison of Three Methods of Fetal Weight Estimation in Patients With Severe and Morbid Obesity

Accuracy of fetal weight estimation is of key importance in antenatal care, as well as in the planning and management of labor and mode of delivery. In order to achieve more accurate prenatal fetal weight estimations and align these with a risk-optimizing mode of delivery, additional tools supporting the standard of use with ultrasound are needed.

The main ultrasonic methods used to calculate the weight of a fetus are based on measurement of fetal abdominal circumference (AC) and estimated fetal weight (EFW) using a formula first described by Hadlock, and the sufficient accuracy of this model has recently been proven.

Leopold's maneuvers have a long-standing tradition in obstetrics and midwifery. By placing both hands on the woman's abdomen the examiner can describe the position of the fetus as well as the level of the uterine fundus and thus detect a disproportion between fetus and the female pelvis. Experienced examiners are able to give a clinical estimation of fetal weight after performing Leopold's maneuvers including symphysis-fundal height and abdominal palpation. Maternal body mass index (BMI) has been shown to affect the accuracy of EFW. For example overweight (BMI>25) patients had found an absolute % error >10% in fetal weight estimation in 42.2% and 24.4% of cases, using Leopold's maneuvers and ultrasound, respectively. Maternal estimation of the fetus weight is as accurate as physicians; clinical estimations, and is advised as a complementary method of assessment. The aim of this study was to compare maternal, clinical and ultrasound estimations of fetal weight in women with severe (BMI>35) and morbid (BMI>40) obesity and to determine the effect of maternal body mass index (BMI) on these estimations.

Pregnant women ≥ 37 weeks and with BMI ≥ 35 with singleton who are admitted before delivery will be offered to participate in the study.

1. A clinical weight estimate will be performed by a trained professional physician using Leopold's maneuvers.
2. An ultrasonographic estimate will be performed in our ultrasound unit and a calculation by the ultrasound machine is based on Hadlock's formula [3] including measurement of biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL).
3. For maternal estimate, patients will be asked to give a fetal weight estimation.