Low Progesterone and Its Impact on Early Pregnancy

Progesterone plays an important role throughout a healthy pregnancy, but what happens when progesterone levels are too low? How does this impact implantation, the growing fetus, and the overall pregnancy? 

We know these are important questions you may have when trying to conceive, especially when seeking reproductive and fertility services from a provider. 

The role of progesterone is essential before conception even takes place, and you will often find during fertility treatment that progesterone supplementation is important during the process as well.

Progesterone’s Role in Early Pregnancy

Before an embryo implants, progesterone plays a key role in your uterus for pregnancy by preparing the endometrium to allow an embryo to stick or implant properly. Progesterone not only helps prepare the lining but also is one of the key hormones that help increase the thickness in the lining that is optimal for implantation to occur. 

Once an embryo has implanted, the role of progesterone shifts and now helps the uterus to expand to accommodate the growing fetus. It also helps prevent contractions that could lead to pregnancy complications, including miscarriage. A miscarriage is a loss of pregnancy prior to 20 weeks gestation.

As pregnancy progresses, progesterone continues to support the growing fetus by helping the uterus to expand and in later pregnancy, progesterone also helps the body prepare for the process of making breastmilk for the baby.

Why is Progesterone Often Supplemented During Fertility Treatment?

Your doctor will often prescribe a form of progesterone during treatment to help support early pregnancy. This could include progesterone in oil or vaginal suppositories. Sometimes, you may be prescribed more than one form of progesterone, depending on your needs and the treatment being provided. 

Progesterone is supplemented because this hormone is essential for a healthy pregnancy. During certain types of fertility treatment, your ovaries may be intentionally suppressed to help prevent cyst formation, requiring the use of exogenous progesterone supplementation that would replace that of a natural cycle. 

For those who become pregnant, progesterone is often prescribed until weeks 8-10 of pregnancy. At that point, the placenta will take over progesterone production to continue supporting the fetus. 

The Problem with Low Progesterone

Low progesterone may be associated with an impending miscarriage, but it is important to note that it is not the cause of the miscarriage. In most cases, the miscarriage occurs first and triggers a drop in progesterone levels, which subsequently leads to bleeding. 

For those getting progesterone supplementation, the doctor will continue monitoring your progesterone levels throughout your cycle and early pregnancy to ensure you absorb enough of the hormone to help protect the growing fetus. For most pregnancies, issues with low progesterone go away once the placenta takes over at around 8-10 weeks. 

When To Seek a Reproductive Endocrinologist

If you have been trying to conceive for more than a year, it’s important to talk to your doctor to get additional testing and learn more about your fertility potential. A reproductive endocrinologist can run some initial bloodwork to help you better understand the hormones in your body and get the assistance you need to help grow your family.

Author

Dr. Meera Shah Meera Shah, MD, FACOG, is a reproductive endocrinology and fertility specialist at NOVA IVF in Mountain View, California. Double board-certified in obstetrics and gynecology, as well as reproductive endocrinology, Dr. Shah is committed to providing the highest level of patient-centered care by combining the latest research in the field with compassionate care that allows patients to navigate through a very difficult time in their lives.