NEJM 2004 vol 351:1927-1929 Linda J. Heffner, M.D., Ph.D.
Advanced Maternal Age – How Old is Too Old?
This study is based on 10 different populations living between the 17th to 20th centuries that did not use contraceptives. Fertility remains relative stable through 30 years of age, at more than 400 pregnancies per 1000 exposed women per year, and begins to decrease substantially to less than 200 at 40-44 years of age. By 45 years of age, the fertility rate is only 100 pregnancies per 1000 exposed women.
At the same time miscarriage, spontaneous pregnancy loss before the 20th week of gestation, increases from 10 percent at 20 years of age to 25 percent at 35-40 years of age, and finally to an astonishing rate of more than 90 percent among women 45 years of age or older.