We’ve been getting a lot of questions about fertility tests and other predictors of fertility from our customers who’re preparing for their fertility treatment with Ovally. For the purpose of this post, we’re going to focus on women’s fertility and what is available to test it, though keep in mind that it’s only half the story. The one predictor of fertility that probably comes to mind for most of us is age. We could write a whole post about the controversies of age-related fertility decline but will focus on hormone levels and fertility tests here. Suffice it to say that some frequently cited data on age-related fertility decline are very old and come with all kinds of confounds, but there is well established evidence that pregnancy success rates for women needing treatment for fertility issues decrease significantly with age, while rates of miscarriage and chromosomal abnormalities increase. A few studies comparing natural conception rates of women in their 30s and 40s have also shown that conception rates decrease and time to conception increases with age.
There is another critical component of fertility that declines with age: The number of eggs a woman carries. It sounds almost inconceivable that 20-week-old female fetuses have 6-7 million eggs. At birth, baby girls still have about 1-2 million eggs, and as teenagers they are down to 300-500k eggs, which continue dying off until menopause. During a typical monthly cycle, 10-20 eggs start maturing, and typically only one gets to ovulate. The remaining 9-19 eggs die every month along with thousands of other eggs that don’t ever begin maturing. The number of eggs a woman has left at any given time is referred to as her “ovarian reserve”.
There are three hormones that have been associated with ovarian reserve: Anti-muellerian hormone (AMH), follicle-stimulating hormone (FSH), and estradiol (E2). Low AMH in particular seems to be correlated with low ovarian reserve. However, these hormones aren’t reliable predictors of your ability to conceive, and you could also have fertility issues that don’t affect their levels. That said, women with low AMH levels tend to enter menopause sooner, and elevated AMH can be a sign of ovarian tumors. The most robust research on AMH, FSH, and E2 demonstrates their link to fertility treatments: For instance, patients with higher levels of AMH tend to be able to stimulate more eggs to mature for the purpose of egg freezing or IVF.
Another way of assessing ovarian reserve is to count the number of antral follicles visible in an ultrasound – there are typically 10-20 in various stages of maturation every month. A transvaginal ultrasound also allows a doctor to assess if you have any abnormalities on your ovaries, the uterus, cervix, endometrium, fallopian tubes, or the pelvic cavity, which could affect your fertility (e.g., ovarian cysts, endometriosis). Such transvaginal ultrasounds are part of the annual OBGYN exam in some countries (but not in the US). AMH levels alone, which several commercially available fertility blood tests now offer, could leave you falsely assured (or falsely alarmed) about your fertility, and an ultrasound provides a fuller picture.
Other hormones that are sometimes tested by fertility blood tests include progesterone (a hormone that’s released leading up to ovulation), prolactin (a hormone that’s involved in milk production and should only be high only if you’ve recently given birth), and luteinizing hormone, which regulates your cycle. All three hormones are linked to healthy ovulation, and an imbalance could point to irregular or lacking ovulation, which you may be unaware of, or other issues affecting fertility. Lastly, testosterone levels are helpful to test as well, as they tend to be higher in patients affected by polycystic ovary syndrome (which I’ll blog about in the future) and other conditions associated with infertility.
In addition to these hormonal indicators, there are many other health factors known to affect fertility, ranging from problematic weight to STDs, smoking, stress, and many more.
What’s the takeaway on fertility assessments? Unfortunately, no test can give you an exact prediction of how long it might take you to get pregnant, or how many years of easy natural conception you have left (especially since sperm quality plays a major role as well). Instead, a good test will check a range of hormones (beyond AMH) and tell you if you’re within a normal hormonal range, as well as interpret your results with all their caveats based on scientific evidence. In addition, we’d recommend reviewing your results with an OBGYN and trying to get an ultrasound as well, especially if the test revealed any potential issues, or if you’re already experiencing any problems (e.g., missing, irregular, or really painful periods, unusually short or long cycles).