I would like to see a study that compares pregnancy results for women who remain childless into their late 30s/early 40s and use birth control and/or have had abortions and those who have been celibate and not used any birth control. I wander if such factors may have a greater effect than just age.
The study was on a large population that never used birth control. The investigators measured the relationship between the age of the female partner and fertility. Infertility rates are now higher in the general population than for the population in this study from the 1950s.
This study found:
By age 30, 7% of couples were infertile
By age 35, 11% of couples were infertile
By age 40, 33% of couples were infertile
At age 45, 87% of couples were infertile
Reference: Tietze C: Reproductive span and rate of conception among Hutterite women. Fertility and Sterility 1957;8:89-97.
http://www.advancedfertility.com/age.htm
I don't think birth control is a direct contributor to infertility, but it is an indirect contributor in that it is a factor in multiple sex partners which can lead to both STD's and abortions which have a known negative effect on fertility.
(p.s. I don't think you meant to use the word celibate in your comparative question since celibate people have a 0% fertility rate which moots any comparison as all non-celibate women would have higher fertility rates than celibates regardless of lifestyle. Perhaps you meant monogamous?)