Are there sex differences in Fetal Abdominal Subcutaneous Tissue (FAST) measurements?

Abstract

Objective To determine if Fetal Abdominal Subcutaneous Tissue (FAST) measurements using antenatal ultrasound differ between male and female fetuses. Study design Women who had an ultrasound examination for fetal growth between 20 and 40 weeks gestation were studied. Women with diabetes mellitus were excluded. The fetal anterior abdominal subcutaneous tissue was measured on the anterior abdominal wall in millimetres anterior to the margins of the ribs, using magnification at the level of the abdominal circumference. The fetal sex was recorded after delivery. Results A total of 557 fetuses were measured, 290 male and 267 female. The FAST measurements increased with gestational age. The FAST increased at the same rate for both male and female fetuses and at any given week there was no sex difference. Conclusions The increased fat composition in females reported after birth was not found in abdominal wall subcutaneous fat measurements using ultrasound during pregnancy. Antenatal centile charts for FAST do not need to be based on sex.