Older mums: getting pregnant over 35

As more women try for a baby in their 30s and 40s, how do your chances of falling pregnant increase as you grow older?

Women who are considering having children after the age of 35, especially if it's a first baby, should be aware of the potential problems associated with 'late' pregnancies:

Reduced fertility The chances of conceiving in any ovarian cycle are one in four in women below the age of 30. The odds get progressively longer from the age of 30 onwards and the rate at which follicles disappear from the ovaries accelerates after 37 years of age, so fertility levels fall even further. Even with IVF, most centres have reported pregnancy rates falling significantly in women over 35.

Miscarriage The risk of miscarriage increases with age. The likelihood of a pregnancy ending in miscarriage is 6.4% in women under the age of 35, but rises to 23.1% in women over the age of 40. Women over 40 who smoke have an even higher miscarriage rate.

Foetal abnormalities The risk of neural-tube defects such as spina bifida does not increase for the older mother. But the risk of Down's syndrome does rise. A woman aged 35 has a one in 300 chance of having a Down's syndrome baby, whereas a woman aged 40 has a one in 100 chance. Although maternal age is not the only risk factor for Down's syndrome, women who conceive after the age of 35 are routinely offered antenatal screening for the condition.

Pre-eclampsia (toxaemia of pregnancy) This is a serious condition that can arise after the 28th week of pregnancy. It is more common in first pregnancies, and in women aged either under 20 or over 35. Women who have their first pregnancy after the age of 35 are therefore particularly at risk. Regular antenatal care is vitally important in the early detection of pre-eclampsia, so is especially recommended for older mothers.

Premature labour Mothers aged between 26 and 35 have the lowest risk of premature labour. The incidence rises progressively in women aged over 35. This is probably because the quality of the placenta in older mothers is more likely to be poor, and so can't sustain a full-term pregnancy.

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