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Women with older partners may be at higher risk of suffering miscarriages irrespective of their own age, according to a study linking the increased chance of a failed pregnancy with men over 40.
Until now it was widely assumed miscarriage rates largely increased with female age only. But
a study into women undergoing artificial insemination with their partner's sperm has found it can also be linked with older men.
Scientists also found pregnancy rates fell as the male partner gets older. This may reflect a decline in sperm quality in men over 40 that affects both the chances of conception and the increased risk of a miscarriage, they said.
It is the first time scientists have discovered such a strong paternal effect on rates of pregnancy and miscarriage.
They suggest that, in future, fertility clinics should look more closely at the age of men as well as the age of women when advising on treatment.
Stephanie Belloc of the Eylau Centre for Assisted Reproduction in Paris said: "Until now ... the message was to get pregnant before the age of 35 or 38 because afterwards it would be difficult. But now the gynaecologists must also focus on paternal age and give this information to the couple.
"We suggest that there is a link between paternal age and DNA decay in the spermatozoa because we previously demonstrated that age is associated with increased sperm DNA fragmentation.
"So maybe there is a link between paternal age and DNA decay that are implied in the miscarriages. I think it's important to consider not only the woman, but both members of the couple in natural conception, but also in assisted reproductive technology [such as artificial insemination and IVF]."
The scientists analysed data gathered at a fertility clinic that performs artificial inseminations directly into a woman's uterus, a technique which improves the conception rate.
They followed up 21,239 cases of these intrauterine inseminations to see whether the age of the man or the woman had any significant effect on the chances of conception and miscarriage.
As expected, they found maternal age was a strong factor in pregnancy rates, with just 8.9 per cent of women over the age of 35 getting pregnant, compared with 14.5 per cent in younger women.
"But we also found that the age of the father was important in pregnancy rates - men over 35 had a negative effect," said Dr Belloc. "And, perhaps more surprisingly, miscarriage rates increased where the father was over 35."
The study found that the miscarriage rate among women with partners aged between 35 and 39 was 18.1 per cent, but 33 per cent for the partners of men aged between 40 and 44.
Dr Belloc said couples undergoing assisted reproductive technology where the man is older than 35 or 40 should consider using intracytoplasmic sperm injection (ICSI), for directly injecting single sperm into an egg, because then the best sperm could be chosen for fertilisation.
- INDEPENDENT