The “age of your eggs” is about the single most important factor in fertility prognosis. Many women are unaware that just because they “eat right, exercise, and have regular periods” they may have exceeded the fertile lifespan of their eggs. Peak fertility for a woman is about age 27, but it changes very little until the mid-30′s, when potential fertility wanes measurably every year, and faster each year than the last. By 40, success rates are only half of what they are below 40, but that’s really not “40-49″ but more like 40 to 42 in practical terms. By ages 43-44, pregnancy achieved with one’s own eggs is often impossible. Women should seek care from a specialist in Reproductive Endocrinology and Infertility EARLY if there has been no conception within one year of unprotected intercourse (unless there is an obvious known cause such as abnormal menstrual cycles or poor sperm parameters, where evaluation should begin immediately), or six months if over the age of 35. (Notice I said “within one year of unprotected intercourse”, not “one year of trying“. Couples often say they “weren’t really trying“, but if you’re not trying not to get pregnant, you are really trying!)
It may not seem altogether fair, since men can be theoretically fertile throughout their lifespans (although even there, older men over forty are less fertile overall than younger men), but the reasons for that may not be so clear. A woman’s egg is easily 1000 times the size of a sperm, and at least 1000 times more complex and “high-maintenance”. Further, all the eggs a woman is ever going to have she has from the time she was about a five-month fetus herself, and she never gets any new ones (or sperm, for that matter–same deal–although compared to an egg, there is not much in a sperm to go wrong, hence their longer effective lifespans). Accordingly, a woman’s eggs are a few months older than she is at every age.
Anyway, to get back to the complexity of the egg, it is well-known that as an egg grows older, there are biochemical processes at which it becomes less efficient–enzymes break down, DNA becomes altered, and so on. One side of this coin is that as a woman’s eggs age, not only is it harder to become pregnant, it becomes much more likely to have a miscarriage even when a pregnancy ocurs. This is why the “liveborn pregnancy rate” is a much more valuable statistic to consider than mere “pregnancy rate” when considering the odds.
A valuable resource is a study entitled ”One Last Chance for Pregnancy: A Review of 2,705 in vitro Fertilization Cycles Initiated in Women Age Forty and Above”. (Klipstein,S. et al, Fertility and Sterility, 2005) . In it, the authors clearly show a dramatic fall in both pregnancy rates and more so in liveborn rates from ages 40 to 44. There was about a 2.6% liveborn pregnancy rate at 44 and 1.9% at 45. There were no pregnancies above age 45.
Another similar reference is ” Analysis of 2,386 consecutive cycles of in vitro fertilization or intracytoplasmic sperm injection using autologous oocytes in women aged 40 years and above”. (Serour,G. et al. Fertility and Sterility, 2010). Here the authors made a strong argument for using donor eggs in women age 43 or above.
Many times a month I tell patients astounded by this news that “Really, it’s not you that are old–you are young, vital, and years from menopuase–but your eggs are old”, and the only way around that reality may be with donor eggs (another topic, another day). Yes, it’s true that there are “tests” you’ve been reading about on the Internet that give some guidance as to whether your eggs are completely past their prime or not, such as “Day 3 FSH” levels and AMH (anti-mullerian hormone) evaluations, but NO test value supercedes the importance of the age of one’s eggs as the prime factor in a woman’s fertility.