In fact, the name progesterone means “promoting gestation.” So it makes sense that too little progesterone might undercut your pregnancy chances.
Here, we explain the role of low progesterone and its effect on your likelihood of getting pregnant — and staying pregnant. And we offer pro tips for getting tested for low progesterone at the right time in your cycle.
How can low progesterone affect my chances of pregnancy?
Too little progesterone can reduce your likelihood of getting pregnant by affecting reproduction in a couple of ways. It may prevent the uterine lining from thickening, potentially lowering the chances of implantation by the egg (1). Low progesterone may also tell the uterine lining to shed too soon, resulting in a short luteal phase, and less success conceiving (2).
In fact, researchers found that women with a luteal phase of 11 days or shorter had more difficulty getting pregnant, per a paper published in Fertility and Sterility (2). In comparison, the average luteal phase is around 14 days (3). (Insider tip: Kindara approximates your luteal phase length based on the day marked as your temperature shift, so you don’t have to count the days manually ).
Lower progesterone is also linked to polycystic ovarian syndrome (PCOS), which is one of the most common causes of female infertility, per the American College of Obstetricians and Gynecologists (4).
How does progesterone affect my risk of miscarriage?
Progesterone is essential for maintaining early pregnancy. Or, in OBGYN-speak, “A defect in corpus luteum function is not only associated with implantation failure but also with miscarriage (5).” So if your corpus luteum isn’t churning out a sufficient level of progesterone, the likelihood of implantation drops and your risk of miscarriage rises.
You’ve probably heard about progesterone treatment to prevent miscarriage — it’s been controversial for some time. The idea is to take progesterone, either with a pill, suppository, or in some other fashion, to shore up a low progesterone level and prevent miscarriage. Some studies with a limited number of patients showed taking progesterone might help avert a miscarriage, but a broad, rigorous study on the theory has been largely MIA, until now (6).
This month, a gold-standard study published in The New England Journal of Medicine found progesterone treatment made no difference in preventing miscarriages among pregnant women with light bleeding early in their pregnancy that put them at risk for miscarriage (6).
Indeed, 75% of the 2,025 women had a live birth in the group that took progesterone, compared with 72% of 2,013 women who took a placebo. This 3% difference isn’t considered statistically significant.
Is low progesterone ever beneficial for my fertility?
Yes! Low progesterone early in your cycle tells your pituitary gland to release follicle-stimulating hormone (FSH), which helps produce a follicle and egg. It’s later in your cycle that low progesterone can cause problems.
If you’re experiencing these symptoms, it’s best to see a doctor. Although we’re big believers in self-care, it’s a given that self-treating low progesterone is a giant no-no.
Also bear in mind that the symptoms we just listed above may be due to stress, hormonal imbalances, or a variety of health issues unrelated to low progesterone. So go ahead and get your levels professionally tested.
What happens during a progesterone test?
Your doctor will measure your progesterone level by drawing a blood sample about 1 week before you expect your period (8), per the American College of Obstetricians and Gynecologists. At the time of your appointment, be sure to share all of the valuable knowledge you’ve gathered about your cycle through charting (you are charting, right?) with your doctor.
Make sure they test you based on your cycle and ovulation, not some average. Since knowledge is power, this know-how empowers both you and your doctor to work in a concerted fashion during your fertility journey.