Does Female Fertility Really Drop off a Cliff After 35?

You've heard it. One in three women over thirty-five won't conceive after a year of trying.

It's in the articles, it's in the consult rooms, and it's the number that makes people book a fertility appointment on their thirty-fifth birthday.

I went and found where it comes from. It's a computer model published in 2004, and the natural-fertility numbers feeding that model come from historical populations — French birth records from the 1670s onward. Women with no antibiotics, no thyroid medication, and five children already.

Modern studies that follow women actually trying to conceive now find 78 to 82 percent of women aged 35 to 39 conceive within a year.

Age matters. It's the strongest predictor we have, and I'm not going to pretend otherwise. But a decline is not a cliff, and nothing happens on your birthday.