Dad's sperm linked to IQ

The results of a relatively small study suggest that children conceived using a fertility technique called intracytoplasmic sperm injection (ICSI) may have slightly lower IQ scores than children conceived naturally or with in vitro fertilisation (IVF).

ICSI is typically used for men who have low numbers of sperm in their semen or who have poor quality sperm. However, it can also be used in cases in which the mother's eggs are difficult for the sperm to penetrate.

In a laboratory, a single sperm is isolated and then directly injected into an egg removed from the prospective mother. If fertilisation is successful, the embryo that develops a few days later is transferred into the mother and the steps are then the same as with IVF.

As reported in the journal Fertility and Sterility, Dr. Sylvia Veen and colleagues from Leiden University Medical Centre, the Netherlands, compared the IQ at age five to eight years of 83 children conceived by ICSI with that of 83 children conceived by IVF and 85 conceived naturally.

They report that the average IQ, based on the Revised Amsterdam Child Intelligence Test, was 103 in the ICSI group, 107 in the IVF group, and 110 in the naturally conceived group.

The four-point difference between ICSI children and IVF children was not considered significant from a statistical standpoint, meaning that it could have occurred by chance. However, the seven-point difference in favour of naturally conceived children versus ICSI children was statistically significant.

"The ICSI children performed worse on all subtests with differences in (average) scores ranging from 0.7 to 2.1," the investigators note.

Veen and colleagues point out that "the clinical significance of the differences in IQ between ICSI children and both IVF and natural conception controls is debatable."

"On the one hand, the (average) IQ of ICSI children was within the normal range," they explain. "On the other hand, a shift of the total ICSI population to lower IQs may result in children crossing borders at the lower edge of the normal range. Indeed, ICSI children more often scored less than 85 than natural conception children."