A twin pregnancy can be more complicated than a single pregnancy. Sometimes twins are smaller than expected for their gestational age. This is called growth restriction, which might happen because of a problem with the placenta or their health.

A new study from the Leiden University Medical Center (LUMC) suggests that a child who receives fewer nutrients in the womb than their identical twin brother or sister is more likely to have developmental problems later in life.

Scientists carefully observed genetically identical twins in which the shared placenta was unevenly distributed during pregnancy. This occurs in 10 to 15% of these twin pregnancies.

They invited 48 pairs of twins between ages 4 and 17 with a growth difference. Scientists accessed their motor skills by performing IQ tests on each of these infants. They observed that the children who were smaller at birth, on average, scored lower in all areas of intelligence compared to their twin siblings. They also had mild psychomotor developmental delay.

Jeanine Van Klink, child psychologist and researcher at the Willem-Alexander Children’s Hospital (WAKZ), explained, “I have been working with this group of twins for about ten years and had always suspected that the smaller of the two developed differently in many cases. We have the first scientific proof that this is the case.”

According to the study, the care and attention for these twins should not stop once they leave the hospital.

Van Klink said, “It is important to keep following these children. We can only detect developmental problems early and offer support if needed.”

Groene said, “In addition, we can now provide the parents of these twins with better information.”

“We are also investigating whether the difference in growth before birth affects the development of the heart and lungs.”

“Furthermore, we have measured the growth of these twins and are using the growth curves from the consultation office to study the growth patterns in the first years of life.”

Van Klink said, “Parents share their experiences, the differences they see within the twins and their concerns with us. This is extremely valuable because, after all, parents know their children best.”

Groene said, “With their help, we gain more insight into the long-term health of these special twins, and in turn, we can make healthcare a little better for them.”

Journal Reference:

  1. Sophie G Groene, Koen J J Stegmaijer et al. Long-term effects of selective fetal growth restriction (LEMON): a cohort study of neurodevelopmental outcome in growth discordant identical twins in the Netherlands. The Lancet Child & Adolescent Health. DOI: 10.1016/S2352-4642(22)00159-6