Cerebral palsy risk in IVF babies halved in past 20 years

The incidence of cerebral palsy among children conceived through in vitro fertilization (IVF) has been halved over the past two decades, although the risk of cerebral palsy remains higher than children who are conceived naturally, according to a Nordic study presented at the ESHRE 2020 Meeting.

The decline was largely attributed to a reduction in twin births in IVF, pointed out presenting author Dr Anne Lærke Spangmose from Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark. 

The results thus provide strong evidence that limiting the number of twin births following IVF can lower the risk of cerebral palsy in children conceived through assisted reproductive technology, highlighted Spangmose.

“[While] multiple embryo transfer is still standard care in many countries … our findings emphasize that single embryo transfer and singleton births should be encouraged worldwide,” she said.

The registry-based cohort study included 111,844 children from three national IVF birth cohorts in Denmark (1990–2010), Finland (1990–2010), and Sweden (1990–2014). The children were followed until 2014 (or 2018 for the Swedish cohort). Their health records were compared against those of 5 million naturally-conceived children. [ESHRE 2020, abstract O-144]

Among the IVF population, the overall prevalence of cerebral palsy consistently dropped from 12.5 cases per 1,000 births in the initial years (1990–1993) to 3.4 per 1,000 births in later years (2011–2014).

In contrast, the prevalence of cerebral palsy declined only slightly from 4.3 to 2.1 per 1,000 births in children who were conceived naturally during the same period.

Nonetheless, the risk of cerebral palsy remained evident in children conceived through IVF vs natural means, Spangmose noted.

The risk of cerebral palsy was almost doubled among children conceived through IVF vs natural means (adjusted odds ratio [aOR] 1.93, 95 percent confidence interval [CI], 1.71–2.17), after adjusting for maternal age, parity, offspring’s sex, and birth country and year. The risk remained elevated after further controlling for plurality (aOR, 1.18, 95 percent CI, 1.04–1.34).

When the analysis was stratified based on multiplicity of birth, the researchers found that among singletons, the prevalence of cerebral palsy has declined from 8.5 to 2.8 per 1,000 births — which is similar to the background population rate.

On the other hand, the rate of cerebral palsy remained stable at 10.9 per 1,000 births for IVF twins during the study.

Compared with naturally conceived children, the corresponding aOR of cerebral palsy was higher for IVF twins (aOR, 1.32, 95 percent CI, 1.10–1.57) but similar for IVF singletons.

According to Spangmose, the birth rates of twins following IVF have declined considerably in Europe, particularly in the Nordic countries whereby IVF twin rates have dropped from ~25 percent in the 1990s to <5 percent currently — similar to the twin rate of 2 percent in the population of naturally conceived pregnancies.

While the exact cause of cerebral palsy remains largely unclear, known risk factors include low birth weight, preterm birth, and twin births, she added.