Fetal thigh measurement may predict adiposity



ORLANDO – Fetal thigh measurement at 28 weeks can help identify babies who are at risk of neonatal adiposity, according to a small exploratory study.

The study also showed that abdominal circumference and estimated fetal weight at 28 weeks’ gestation were not correlated with adiposity at birth, nor were prepregnancy body mass index, maternal weight gain, or birth weight.

With a nation facing an obesity epidemic, the study may provide yet another tool to combat the trend by opening the possibility of fetal-based interventions, hence reducing the risk of childhood obesity.

Compared with birth weight, adiposity at birth has been known to be a stronger predictor of childhood obesity, said Dr. Gaea S. Moore of the University of Colorado, Aurora, who presented the abstract at the annual meetingof the Society of Gynecologic Investigation.

But, there’s not yet a good way of measuring how much fat the baby is going to have, said Dr. Anna L. David of University College London Elizabeth Garrett Anderson Institute for Women’s Health, London, who moderated the session. "So this study looks very promising," she said.

While 2D fetal ultrasound has not been a strong tool in measuring fetal adiposity, adding 3D fractional limb volumes (FLV) has helped improve the prediction of both adiposity at birth and macrosomia.

Dr. Moore and her colleagues conducted a prospective cohort study of 18 pregnant women, collecting data from standard 2D ultrasound biometry and mid-thigh cross sectional areas (MTA), and 3D FLV, measuring thigh volume at the 50% of the femur, using a 5-slice technique. Both measurements were analyzed with the 4D View software.

Seven of the 18 subjects were excluded due to poor image quality.

The mean age of mothers was 30 years, with prepregnancy body mass index of 26, parity of 0.83, and the mean gestational age at birth of 39 weeks and 3 days.

Researchers measured neonatal body composition with air displacement plethysmography (Pea Pod) 14 days after birth. The mean birth weight of the infants was 3,383 g, and the mean body fat was 10.68%.

Analyses showed that fetal thigh measurement at 28 weeks correlated with neonatal adiposity. FLV and MTA correlated with adiposity at 28 weeks when normalized for femur length (FL). (FLV/FL, r = 0.77; P = .005. MTA/FL, r = 0.75; P = .007)

The correlation further improved with adjustment of thigh volumes by femur length, and by adjustment for Pea Pod timing and gestational age adjustments.

The study opens the possibility of obtaining data that could lead to a conversation with pregnant moms whose babies might be at risk of neonatal adiposity, Dr. David said. "Maybe there’s an intervention that could reduce the adiposity," she said, whether it’s giving the mother medications that would reduce the sugar going across the placenta, or manipulation of diet.

She also pointed out that larger studies were needed, and that 28 weeks may not be the optimum time for measurement, as seven subjects were excluded due to poor image quality. "At 20 weeks there’s relatively more fluid around the baby, so maybe that might be a better time to take the measurement." She said that the measurement’s accuracy is yet to be determined.

Dr. Moore and her colleagues have obtained measurements at 36 weeks, but have not analyzed the data. She said the group had not evaluated data for earlier than 20 weeks’ gestation.

Dr. Moore and Dr. David reported no disclosures.

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