Reducing Triplets To Twins Linked To Fewer Brain Disorders

What was studied

This study looked at liveborn children from trichorionic triamniotic triplet pregnancies in Denmark that were diagnosed at the routine first-trimester scan. The researchers compared pregnancies managed with fetal reduction from 3 fetuses to 2 with pregnancies that were not reduced.

They used national health and pregnancy records and included eligible triplet pregnancies with estimated due dates from 2008 through 2018. They followed 625 liveborn children from birth until they developed one of the study outcomes, died, emigrated, or reached the end of follow-up in 2022. The main outcome was a combined measure of neurodevelopmental disorders: epilepsy, cerebral palsy, or intellectual disability.

What they found

Over a median follow-up of 9.3 years, 34 children were diagnosed with at least one of the studied neurodevelopmental disorders. The estimated risk by age 15 was lower in children from pregnancies managed with fetal reduction than in children from pregnancies without reduction.

The cumulative incidence by age 15 was 4.2% after fetal reduction and 10.7% without reduction. After adjustment for maternal age, educational level, and assisted reproduction, fetal reduction was associated with a lower hazard of these disorders overall. For epilepsy alone, the estimates were in a similar direction, but the numbers were small and the estimates were imprecise.

Limits of the evidence

This was an observational cohort study, not a randomized trial, so it cannot show that fetal reduction itself caused the lower risk. The two groups may have differed in ways that were not fully measured or adjusted for.

The total number of children with disorders was small, especially for each individual diagnosis, so some estimates were imprecise. The study only included one type of triplet pregnancy in Denmark, so the findings may not apply to other kinds of multiple pregnancies or to other countries and health systems.

For families and caregivers

For families facing this specific type of triplet pregnancy, this study found that fetal reduction from 3 fetuses to 2 was associated with a lower long-term risk of the severe neurodevelopmental disorders studied among liveborn children. The disorders studied were epilepsy, cerebral palsy, and intellectual disability.

This does not mean the procedure is right for every pregnancy, and the study does not answer every question about risks and benefits. But it may help families and clinicians discuss possible longer-term child outcomes as well as short-term pregnancy outcomes.

What to watch next

More large studies in different settings, with longer follow-up and careful adjustment for differences between families who did and did not choose reduction, could help clarify these findings.

Terms in this summary

fetal reduction

A procedure that lowers the number of fetuses in a multiple pregnancy, such as reducing triplets to twins.

cohort study

A study that follows groups of people over time and compares outcomes between them.

neurodevelopmental disorders

In this study, diagnoses of epilepsy, cerebral palsy, or intellectual disability.

cumulative incidence

The estimated chance that an outcome happens over a set period of time.

hazard ratio

A measure that compares how often an outcome happens over time in one group versus another.

adjusted

Statistically corrected for some differences between groups, such as maternal age, education, and assisted reproduction.

trichorionic triamniotic triplets

A triplet pregnancy where each fetus has its own placenta and its own amniotic sac.