Children born out of fertility procedures such as in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) are known to be at an elevated threat of cerebral palsy. While the risk is known the underlying factors are not clear. The risk could be due to the fertility treatment, the higher occurrence of multiple or preterm, or a predisposed condition associated with the couples' original infertility.

A research led by Dr. Jin Liang Zhu, at the Danish Epidemiology Science Centre at the University of Aarhus, Denmark, now propounds that primary infertility is not the reason for the increased risk of cerebral palsy. Dr Zhu is probably the first to study the link between the time for a couple to attain a pregnancy and the perceptible threat of cerebral palsy.

The data of births was classified for the study by comparing births with 0-2 months of waiting time to pregnancy with those born at 3-5 months waiting time, 6-12 months, and longer than 12 months, as well as those born after IVF/ICSI, ovulation induction with or without intrauterine insemination, and unplanned pregnancies. Parents who conceive earlier are classified normally fertile, as opposed to a waiting time of a year or more, indicating some degree of subfertility.

Post factoring in dynamic reasons that could influence the health of the baby, such as the age of the mother, parity, exposure to tobacco, the sex of the child, full term or preterm pregnancy, and whether it was a multiple birth, the researchers established no considerable association involving the time to pregnancy and the risk of cerebral palsy. The observation includes children of a spontaneous pregnancy, even after a waiting time to pregnancy of a year or more.

Dr. Zhu said: "Our research enabled us to examine whether untreated subfertility, measured by time to pregnancy, might be the reason for the higher risk of cerebral palsy after IVF/ICSI. Our results showed that this was not the case because, even for couples who took a year or longer to conceive, there was no statistically significant increased risk if they conceived spontaneously."

While the researchers adjusted the risks associated with preterm births and multiple pregnancies, they found that children born after IVF/ICSI treatment had twice the risk of cerebral palsy as compared to children born of spontaneous conception with a waiting time of 0-2 months. When the children born out of IVF/ICSI treatment were compared to children conceived spontaneously after a waiting time of more than a year, the risk diminished.

Dr. Zhu said: "It is important to stress that the risks of cerebral palsy after IVF/ICSI are low. Out of more than 90,000 children in the Danish National Birth Cohort, born between 1997 and 2003, only 165 (0.18%) were diagnosed with cerebral palsy. Of the 3,000 children in this cohort born after IVF/ICSI, only 17 (0.57%) had cerebral palsy.

This means that the absolute risk of having a child with cerebral palsy after IVF/ICSI treatment is still low – approximately one in 176 babies – and this risk is even lower if the children are born as a result of a single embryo being transferred to the mother's womb, thus avoiding the risks of a multiple pregnancy. Further analysis of the data showed that, when children born after IVF/ICSI were compared with children conceived spontaneously after a waiting time of more than 12 months, the elevated risk of cerebral palsy reduced and was no longer statistically significant."

Dr. Zhu concluded: "More research is needed into why there might be an increased risk of cerebral palsy associated with IVF/ICSI, besides the pathway of multiple pregnancies and preterm births. It is also important to remember that IVF/ICSI techniques have developed and improved considerably since 2003 when the youngest children in our study were born."