Research by NIEHS epidemiologist Donna Baird, Ph.D., and colleagues suggests an accepted predictor of fertility in women needs rethinking.
Baird and colleagues funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), found that a common test to estimate the number of eggs remaining in a woman’s ovaries does not predict fertility for older women with no history of infertility.
The study was published Oct. 10 in the Journal of the American Medical Association (JAMA).
Ovarian reserve and fertility
The research team followed 750 women, ages 30-44 years, who enrolled in the Time to Conceive study. The scientists were interested in a trio of hormones that are correlated with the number of eggs remaining in a woman’s ovaries, which is known as ovarian reserve.
- Antimullerian hormone (AMH).
- Follicle-stimulating hormone (FSH).
- Inhibin B.
Declines in AMH and increases in FSH are associated with declines in ovarian reserve. The scientists wanted to know whether a decline in ovarian reserve was associated with a decrease in fertility in older women without known fertility problems.
Study participants were followed for up to 12 months in their attempts to naturally conceive. The researchers anticipated that women with biomarkers that indicated low ovarian reserve would either take longer to conceive or not conceive at all during that time.
The analyses showed that the chance of conception did not differ significantly among women grouped by measured levels of the three substances. This held true for the cumulative probability of conceiving both by 6 and by 12 menstrual cycles.
Egg quality may matter more than number of eggs
The researchers were surprised by the findings. Even subanalyses among the oldest group of women in the study, those ages 38-44 years, showed no evidence of a link between the biomarkers of ovarian reserve and fertility.
"Although both ovarian reserve and fertility decline with chronological age when looking at cross-sectional data, there may be little association between a given woman’s ovarian reserve and factors that affect her fertility, such as egg quality," the authors wrote.
"We have long known that as women age, their fertility declines," Baird said. "We anticipated that the biomarkers of ovarian reserve would better identify those with low fertility for their age, but they did not. Age still seems to be our best predictor of fertility in older women."
"Our study suggests that younger women with biomarker levels indicating lower ovarian reserve should not become anxious that they won’t be able to have a baby," said lead author Anne Steiner, M.D., from the University of North Carolina at Chapel Hill, in an NICHD press release.
A question of public health
One of the many strengths of the study was that both serum and urinary FSH were measured and evaluated. Home tests of urinary FSH are commercially available for women to use as a fertility test. The authors noted that there is little previous research to support their use, and the new findings suggest that the tests are unlikely to be of benefit.
The researchers designed this study to answer the important public health question of whether diminished ovarian reserve is a cause of infertility in women of late reproductive age. “These findings do not support the use of urinary or blood FSH tests or AMH levels to assess natural fertility for women with these characteristics,” the authors concluded. The characteristics the authors referred to are women aged 30-44 years, without a history of infertility, who had been trying to conceive for 3 months or less.
Steiner AZ, Pritchard D, Stanczyk FZ, Kesner JS, Meadows JW, Herring AH, Baird DD. 2017. Association between biomarkers of ovarian reserve and infertility among older women of reproductive age. JAMA (14):1367–1376.