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Cerebral palsy among IVF children decreased by more than 50% in the last 20 years, researchers reported.

The crude risk of cerebral palsy among children conceived via assisted reproductive technology (ART) dropped from 0.9% to 0.3% from 1990 to 2010, while the risk remained stable among children conceived naturally, reported Anne Lærke Spangmose, MD, of the Fertility Clinic Rigshospitalet at Copenhagen University Hospital in Denmark.

While the prevalence of cerebral palsy among IVF singletons declined during the study period (from 8.5 to 2.8 per 1,000 births), it was stable for IVF twins, indicating that multiple pregnancies heighten risk, Spangmose presented at the .

"High rates of twin births after ART have caused criticism because of the severe complications related to twin pregnancies, including cerebral palsy," Spangmose stated in the presentation.

"Multiple embryo transfer is still standard care in many countries," she said in a press release. "Our findings emphasize that single embryo transfer and singleton births should be encouraged worldwide."

In a , researchers found a significantly increased risk of cerebral palsy among ART-conceived infants. While the absolute risk was small, cerebral palsy became the most common developmental birth defect associated with IVF.

The present study by Spangmose and colleagues indicates that while the risk of cerebral palsy with IVF has decreased with a rise in rates of single embryo transfer, that of twin births is not changed.

"The underlying attributable risk of CP is tied to plurality of pregnancy," said Alan Penzias, MD, a reproductive endocrinologist at Boston IVF and associate professor of obstetrics, gynecology, and reproductive biology at Harvard Medical School. "In other words, twin pregnancies yield more cases of children with CP than singleton pregnancies."

Penzias, who was not involved in this research, said that this research was able to distinguish risk among both singleton and twin pregnancies -- conceived either with ART or spontaneously -- in a way that previous studies have not. "The study underscores the relevance of single embryo transfer in IVF," he told 番茄社区app.

Spangmose and colleagues obtained data from the Committee of Nordic ART and Safety (CoNARTaS) cohort, which contains information from national ART- and patient registries from Denmark, Finland, and Sweden. The data covered around 55,000 IVF babies and more than two million spontaneously conceived children. The researchers grouped the data by birth year in the following time periods: 1990-1994, 1995-1999, 2000-2004, and 2005-2010. Adjustments were taken for maternal age, parity, child's sex, country, and birth year.

Overall, 0.6% of IVF children and 0.3% conceived spontaneously were diagnosed with cerebral palsy. Among babies conceived via ART, around 37,000 were single pregnancies, 17,000 were twins, and almost 800 were high-order multiples.

Risk of cerebral palsy for ART-conceived babies was about double compared to those that were conceived spontaneously (aOR 1.93, 95% CI 1.71-2.17). After adjustment for plurality, the risk estimate was attenuated but remained significantly increased with ART (aOR 1.18, 95% CI 1.04-1.34).

The risk was higher for ART-conceived singletons (aOR 1.32, 95% CI 1.10-1.57), but was similar for both IVF and naturally conceived twins.

Spangmose and colleagues acknowledged that although they adjusted for major covariates, this observational study may be subject to residual confounding.

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