Twins are found to start pregnancy smaller than previously thought, according to new research by the National Institutes of Health (NIH). This ultrasound-based study showed that twins, starting at 15 weeks of pregnancy, have less fat tissue and muscle mass compared to singletons. This finding, subject to further research confirmation, could help guide physicians in the monitoring and management of twin pregnancies.
Data analyzed by researchers included 3D ultrasound scans from 2,604 singleton pregnancies and 315 twin pregnancies, where all twin pairs had separate placentas. The analysis found significant differences between the thigh volumes of twins and singletons, with twins having a smaller thigh fat to lean ratio, displaying 2.7 to 4.2% less fat from 15 to 37 weeks. Prior research with 2D ultrasound scans noted decreased twin growth only in the early third trimester, from 28 to 40 weeks.
The reason for twins being smaller early on is not thought to be due to competition for nutrients, given the placental development at that stage. Instead, it is hypothesized that twins’ smaller size may help accommodate their increasing need for resources later in pregnancy.
This study was led by Jessica Gleason, Ph.D., and Katherine Grantz, M.D., from the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development, and has been published in JAMA Pediatrics. "Jessica Gleason, Ph.D., a perinatal epidemiologist, is available for comment."
The National Institutes of Health (NIH) comprises 27 Institutes and Centers and supports research into medical issues including common and rare diseases. More information can be found on their website.
