For a variety of reasons, many women are delaying childbearing, and there is an increasing number of women in their late 30s and 40s who are seeking assisted reproductive technology (ART) to achieve pregnancy. The average age of parenthood has increased for men and women in Australia in the past 20 years. Both men and women underestimate the impact of age on their fertility and the chance of becoming pregnant. Fertility begins to decline in women from the age of 25, and becomes a significant factor after the age of 35. This is due to a decline in the egg quality with age, rather than decreasing egg numbers. Further, ART cannot compensate for the egg quality as women get older. In the general population, the chance of falling pregnant in any one month, and having a live baby (for couples who are actively trying for pregnancy) is 17% when the women is age 30, 12% at 35, and 5% at the age of 40. And in Australia and New Zealand in 2010, for women aged between 30-34 having IVF treatment, the take home baby rate was 27% per cycle. In women aged 44 and older, it was less than 1%. In women too, the risk of miscarriage and chromosome problems – most importantly Downs syndrome, or Trisomy 21 – increases as women get older. At age 35, the risk of a spontaneous miscarriage following ART treatment is 20%. The risk of Downs syndrome at age 35 is around 1 in 350, at age 40, 1 in 90, and at age 45, 1 in 25.
Men don’t escape age related fertility problems. Although much less obvious than the effect of age in women – the strongest predictor of success with ART is the woman’s age – it is accepted that male fertility declines after the age of 45, the time taken to achieve pregnancy in his partner increases, and the risk of developmental and genetic defects in children, such as autism and single gene defects, increases when the male partner is over 40.
The number of eggs that a woman has can be determined by a blood test (AMH) or by a scan that confirms the number of small, immature eggs sacs that she has in each ovary. This can be very useful information in advising women who are considering pregnancy. Some women in their early 30s have been found to have a surprisingly low level of egg reserves, and should be trying for a pregnancy as soon as possible. Egg freezing is another option, if they have no current partner.
Ref. Fertility Society of Australia, Pre-conception Special Interest Group.