NEW YORK (Reuters Health) – Children born after in vitro fertilization (IVF) have an increased incidence of neurologic disorders, especially cerebral palsy, results of a study conducted in Sweden suggest.
A significant proportion of the risk can be explained by the high frequency of twin pregnancies following IVF, a finding that leads Dr. Bo Strצmberg, of the University Children's Hospital in Uppsala, and associates to recommend the transfer of only one embryo during IVF.
The study, reported in The Lancet for February 9, included 5680 children born after IVF in Sweden between 1982 and 1995. These subjects included 2060 twins. Dr. Stromberg's group compared the incidence of neurologic problems in these children with that in two control groups: one group of 11,360 age- and sex-matched children selected from the Swedish Medical Birth Register, and a second group of 4120 age-matched control twins.
The investigators found that 101 children of the IVF cohort and 201 of the control subjects had at least one neurologic disorder. The odds ratio for the whole IVF cohort was 1.7 compared with the control group. After exclusion of twins from the analysis, the odds ratio for singleton IVF children was 1.4.
The unadjusted risk of having cerebral palsy was increased 3.7-fold among those born after IVF, but the risk in IVF twins was no greater than for control twins. The risk of developmental delay was quadrupled by IVF. While singleton IVF children remained at increased risk for developmental delay after adjusting for low gestational age, sex, and maternal age, the difference was not significant compared with control subjects.
Dr. Strצmberg's group estimates that the prematurity rate among IVF children would be reduced by about 60% if only one embryo was implanted during the IVF procedure. "Thus, the practical clinical conclusion must be that only one in vitro fertilized embryo should be transferred in most instances," the researchers emphasize.
In an editorial, Drs. David L. Healy and Kerryn Saunders, of Monash University in Melbourne, Australia, wonder whether "the IVF process is deficient in some way for the development of the fetal motor system or that infertility itself is an independent factor."
They do agree with Dr. Stromberg's team that there should be a shift from multiple to single embryo transfer in IVF, but add that clinical studies are necessary to understand the absolute risk associated with the procedure.
Lancet 2002;359:459-460,461-465.
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