Progesterone plays in important role in a woman's fertility, both by building up the endometrial lining and triggering it to be shed during menstruation when no pregnancy occurs. Without the proper levels of progesterone in relation to estrogen, women experience irregular cycles, and a host of physical complaints. Progesterone also plays and important role in pregnancy. Most of its functions are that of protector, making sure your baby stays put and stays nourished until it's time to enter the world. It has different roles in each stage of pregnancy and even helps signal delivery time.
Endometrium
It's progesterone's job to create that thick endometrial lining inside of the uterus. When progesterone levels are rising, this layer builds. If they stay high or continue to rise, the uterus will hold on to this layer in anticipation of implantation. If they drop, this layer will shed. According to the American Pregnancy Association, once the embryo has implanted, progesterone directs the endometrium to excrete nutrient-rich fluids to sustain the embryo until the placenta takes over. The placenta not only takes over nourishing the embryo, but also takes over the majority of progesterone production.
Contractions
According to Anandi Subramanian, M.D., progesterone plays in important role in smooth muscle control. High levels of progesterone keep the smooth muscles from contracting, which keeps the fetus in place. The downside to this protection is that other smooth muscles are also affected, which is why pregnant women often report heartburn and acid reflux.
Mucus Plug
According to the American Pregnancy Association, progesterone causes cervical changes. Progesterone prompts the cervix to thicken during pregnancy. It also prompts the cervix to create a thick mucus plug responsible for keeping bacteria out of the uterus and keeping important fluids in. When progesterone levels drop at delivery, the mucus plug breaks down and the cervix begins to open and thin.
Miscarriage
Women with insufficient progesterone levels are at a high risk of miscarrying. Because progesterone builds the endometrium and keeps it from shedding, the fertilized egg is safe in this nutritious layer. If estrogen levels are not high enough, the endometrium can either be too thin to support the embryo or can start shedding like during menstruation. According to the American Pregnancy Association, low progesterone levels can also indicate tubal or ectopic pregnancy.
Delivery
When it's time for your baby to be born, your progesterone level will drop dramatically. This drop triggers your uterus to begin contracting. These contractions help move the baby down through the pelvis and through the birth canal. Women who are at high risk for pre-term or premature birth are often treated with progesterone. According to Sarah J. Kilpatrick, M.D., PhD., a series of tests and trials indicated a 36 percent drop in pre-term birth rates in women who received progesterone injections while pregnant.
