Growing concern over fertility and the controversy of preserving it has inspired a Danish research team to assess what, exactly, drains a woman's ovarian reserves, and they concluded that the oral contraceptive pill could be a major culprit, at least temporarily.
Ovarian reserve is a measure of the ovary's capacity to produce fertile oocytes (egg cells). Modern science assesses it via two measures: levels of anti-Mullerian hormone (AMH) in the blood and the number of early (antral) follicles in the ovary.
The latter is quantified by means of a vaginal ultrasound in a test of antral follicles count (AFC), which coupled with AMH testing provides the most reliable measure of fertility, with the two considered indicators of ovarian age.
Researchers tested 833 women between the ages of 19 and 46 and found the AFC measurements 16 percent lower in pill users and AMH levels down 19 percent.
An unexpected additional finding was that pill users' ovaries were between 29 and 52 percent smaller than those of non-pill users, particularly in the youngest of the subjects, between the ages of 19 and 29.9.
AMH was still up to 30 percent lower and AFC up to 20 percent lower in pill users after the results were statistically adjusted for age, BMI, smoking, maternal age at menopause, maternal smoking during pregnancy and prematurity.
"We expected to find an effect of the Pill," says Dr. Katherine Birch Petersen, from the Copenhagen University Hospital in Denmark. "But during the project we were surprised at the quantified effect on ovarian reserve parameters as defined by anti-Müllerian hormone, antral follicle count and ovarian volume."
To what degree the pill's effects on the ovaries are permanent and how long they last is yet to be discovered, says Dr. Birch Peterson, who remains optimistic that they are temporary but says additional research is necessary to better understand the recovery phase after women stop taking the pill.
Although statistics indicate plenty of pill users eventually become pregnant, the effects of long term pill use have remained a concern.
Dr. Birch Peterson advises pill users not to count on AFC and AMC tests as an accurate measure of fertility and says that tests should be repeated three months after having stopped pill use for a better measure of fertility potential.
"The Pill may mask a severely diminished ovarian reserve," says Dr. Birch Peterson, "and this is important to recognize."
The study was presented Monday the European Society of Human Reproduction and Embryology (ESHRE) Annual Meeting in Munich by Dr. Birch Petersen.
