20 November 2009

Assisted reproduction, birth defect link

A new study has found a higher rate of birth defects among babies conceived by assisted reproduction compared to babies conceived naturally.


A new study has found a higher rate of birth defects among babies conceived by assisted reproduction compared to babies conceived naturally.

In the study, almost 3% of infants conceived with assisted reproduction were diagnosed with a major birth defect, compared to less than 2% of babies conceived naturally, Dr Darine El-Chaar and colleagues from The Ottawa Hospital in Ontario, Canada and colleagues found.

The investigators looked at all deliveries in the province of Ontario in 2005 for which information was available on reproductive assistance.

Their analysis included 43 462 babies conceived naturally; 298 whose mothers had been given drugs to promote ovulation; 173 conceived when sperm was injected into the mother's uterus (intrauterine insemination); and 319 conceived by in-vitro fertilisation (IVF).

What the study found
Among infants conceived with any type of assistance, 2.91% were diagnosed with a major birth defect in the womb or soon after birth, compared to 1.86% of the babies conceived naturally.

These infants also were more likely to have birth defects involving the gastrointestinal system, the cardiovascular system, or the muscles and skeleton, although their risk of neural tube defects such as spina bifida or facial defects such as cleft palate was not increased.

When the researchers looked at the assisted reproduction techniques separately, they found that 2.35% of those born after ovulation induction, 2.89% of those born via intrauterine insemination, and 3.45% of those born via IVF had major birth defects.

However, the researchers note, because the numbers of women in these individual groups was small, the findings could have been due to chance, and the differences were not statistically significant.

Age of mothers could be factor
The average age of the mothers who had conceived naturally was around 29, compared to about 32 for those who had ovulation induction, 34 for those who underwent intrauterine insemination, and 35 for those who conceived via IVF.

It's scientifically plausible, the researchers note, that babies born with assisted reproduction would be at greater risk for major birth defects, "given the interventions required in these treatments."

One contributing factor could be the greater age of mothers -- and fathers -- who undergo this treatment, they add. "Further research in these interventions is needed to clarify each individual contribution," the researchers conclude. – (Reuters Health, November 2009)


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