Medical Research

Why You Shouldn't Use Fertility Tests to Predict Your Ability to Get Pregnant Naturally

Despite the marketing messages pushed to so many women that AMH and FSH are “fertility predictor tests” there has been little-to-no data demonstrating that these these hormone levels have any correlation with natural fertility for women who haven’t tried to conceive, have no reason to believe they’re infertile, and plan on trying to conceive naturally.

Why this study is important

This study was prospectively designed, and was the largest study to date examining the impact of AMH levels and FSH levels on ability to conceive naturally. While it’s not perfect, it does give us a window into what AMH and FSH tests are, and are not, capable of. The basic finding: women who had low AMH levels didn’t differ in their ability to conceive from women with normal AMH levels and, similarly, women with high FSH levels didn’t differ significantly from women with normal FSH levels.

Details of this study

The study, published in JAMA, and followed women aged 30 - 44, who had been trying to conceive naturally for less than three months.

Of women who had low AMH levels, defined as less than 0.7 ng/mL, 65% conceived within six menstrual cycles, and 84% conceived within 12 cycles. That’s compared to women with normal AMH values, defined as 0.7 - 8.4 ng/ML, of whom 62% conceived in six cycles, and 75% conceived in 12 cycles. There was no statistically significant difference between the three groups.

Of women who had low blood levels of FSH, defined as less than 10 mIU/mL, 62% conceived in six cycles and 75% conceived in 12 cycles. For the group with high FSH, above 10 mIU/mL, 63% conceived in six cycles and 82% conceived in 12 cycles. There was no statistically significant difference between the two groups.

There were some weaknesses in this study. Most notably the sample size was reasonably small and thus there is a chance the group studied isn’t totally representative of patients at large.

Further, the investigators used conception as the primary endpoint, rather than live birth, the gold-standard in fertility studies. Conceiving and delivering a healthy live birth are often miles apart. In this context, a related study to this one was recently published in Fertility & Sterility, and showed a correlation between decreased ovarian reserve and increased miscarriage rate, and that is not accounted for here.

The investigators were also unable to capture information about hormonal contraception that women used in the few months before they began the study. Finally, the sample size prevented the investigators from examining whether women with extremely low AMH levels, less than or equal to 0.1 ng/mL, have a harder time conceiving than women with diminished ovarian reserve but higher AMH levels.

We’d like to see more studies like this in the coming years, with even larger numbers, to confirm this finding, and give greater insight into the question of how these hormonal levels relate, if at all, to our ability to conceive naturally.

The Takeaway

This study, for the moment, makes AMH and FSH test results appear uncorrelated to a woman’s ability to conceive. This means the women who are planning on using these tests to gain insight into whether they can conceive now or in the future should exercise extreme caution.

It’s common for women to hear they have slightly, or severely, low AMH and be devastated, assuming this is a “diagnosis” of infertility. Low AMH likely does mean they would have a harder time retrieving a lot of eggs in an egg freezing cycle but, at least based on the information in this study, it seems those women should have no reason to assume they’ll have a harder-than-average time conceiving naturally.

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