Feb. 7, 2002 -- In vitro fertilization has blessed couples around the world with babies. But a new study suggests that those babies may be at increased risk of developing neurological disorders, especially cerebral palsy.
"These risks are largely due to the high frequency of twin pregnancies, low birth weight, and prematurity among [IVF] babies," says lead author Bo Stromberg, MD, in a press release. Stromberg is an associate professor of pediatric neurology at Uppsala University Children's Hospital in Sweden. His paper appears in this week's The Lancet.
IVF is still "a viable option for infertile couples," he tells WebMD. "However, it is our duty to inform them about the risks so they can decide if this is a treatment they can accept."
To reduce that risk, "we strongly suggest that only one fertilized embryo be implanted," Stromberg says.
Researchers have long realized that IVF-conceived babies often result in multiple births, preterm births, and infants born with low birth weights. However, few studies have looked long-term at these babies and their neurological development, says Stromberg.
Cerebral palsy itself has long been linked with multiple births and complications of prematurity, "because these babies are born small and early," says Charles Brill, a pediatric neurologist at Temple Children's Hospital in Philadelphia. "But I've never considered IVF one of the potential causes."
Cerebral palsy is a disorder involving the central nervous system, typically caused by an injury to the brain during infancy. The disorder can be mild, but in its more severe form, there is paralysis and uncontrollable muscle spasms.
Stromberg's results are "a bit disturbing," Brill tells WebMD. "Couples need to have these facts to make an informed decision." And more research is needed to firmly establish the pattern, he adds.
The study itself involved analysis of records for 5,680 IVF babies born between 1982 and 1995. The children with various disabilities were enrolled at 26 rehabilitation centers in Sweden. Researchers also looked at a data from a nationwide register of blind and other severely visually impaired children.
Their aim was to look for patterns of severe neurological disabilities, mental retardation, and severe visual defects in these children.
They found that the most frequent diagnoses were cerebral palsy, developmental delay, congenital malformation, mental retardation, chromosomal aberration, and behavioral disorders.
But when they took a closer look at 2,060 twins in this group, they found that IVF children -- especially twins -- were nearly three times more likely to have cerebral palsy than children in the general population, says Stromberg.
IVF children also had a four-fold increased risk of developmental delay.
Other factors, like the mother's age, did not seem to increase risk for neurological problems, says Stromberg.
"The results of this study are important," writes David L. Healy, an obstetrics/gynecology professor at Monash University in Melbourne, Victoria, in an accompanying editorial. "If the high prevalence is a true result, then the question is whether the IVF process is deficient in some way."
"The high prevalence of cerebral palsy ... seems to be due to the high frequency of twin and higher multiple pregnancies," writes Healy. "Senior figures in the U.S. have recently pleaded for a reduction of twin and higher-order multiple pregnancies to minimize the short-term and long-term damage to babies and mothers."
While it does indicate a pattern, Stromberg's paper does leave unanswered questions: whether the IVF was natural-cycle or stimulated cycle or whether gamete intrafallopian transfer, fresh or frozen embryos, or intracytoplasmic sperm injection were involved, Healy points out.
Nevertheless, the study points to a "need for a shift from multiple to single embryo transfer," Healy says. He, like Brill, calls for more research. "What an infertile couple really needs to know, though, is not their relative risk of having a child with cerebral palsy should they have an IVF baby, but their absolute risk -- which remains to be established."