Age and your chances, with the numbers that are usually left out
The decline is real. It is also slower than the way it is usually described.
Female age is the strongest single predictor of how quickly a couple conceives. That is not in dispute. What is worth seeing is the actual size of it.
In 782 couples keeping daily intercourse records across seven European centres, the proportion who did not conceive within twelve cycles was:
| Woman's age | Did not conceive within 12 cycles | Did conceive within 12 cycles |
|---|---|---|
| 19 to 26 | 8% | 92% |
| 27 to 34 | 13% to 14% | 86% to 87% |
| 35 to 39 | 18% | 82% |
The authors also estimated that complete sterility, meaning no chance at all without treatment, ran at about 1% and did not change with age. And among couples who had not conceived after twelve cycles, between 43% and 63% conceived during a further year of trying.
A separate contemporary study followed 2,962 North American couples who had been trying for three cycles or less. Cumulative pregnancy within twelve cycles ranged from 79.3% at ages 25 to 27 down to 55.5% at ages 40 to 45. Fecundability fell in a roughly straight line, with the sharpest drops after 37.
One thing these numbers cannot do is tell you about yourself. They are averages from groups of women who had already been selected in various ways, mostly white, mostly well educated, and in the European study mostly experienced at tracking their own cycles. Your own number is not in this table.