11/07/2025
New twins study! Maybe meant to be smaller? Have a look
It is assumed that twins grow more slowly because the uterus can’t keep up with the needs of two babies. To determine when this is happening, twin growth is evaluated according to the same growth chart as singletons. This leads to high percentages of twins being diagnosed as growth restricted and to the consequent management, including early delivery, that may follow that diagnosis.
A new study challenges this assumption. What if, theorized the researchers, slower growth is actually an evolutionary adaptation to allow the uterus to nourish two babies to maturity? To test their theory, they did serial ultrasound measurements of growth rates in twin and singleton pregnancies and found that even at 15 weeks—long before the demands of two babies would challenge uterine capacity to nourish both of them—twins already had less fat compared with singletons. This finding supports their theory and argues, according to a commentary on the study,* for developing a fetal growth chart specific to twins.
*Melamed N, Hiersch L. New Insights Into Fetal Growth in Twins-Pathology or Benign Adaptation? JAMA Pediatr 2025;179(6):594-6.
https://bit.ly/3ZJ7U5A
