Progesterone is one of the hormones instrumental in helping a woman become pregnant and maintain the pregnancy. If progesterone levels are low in early pregnancy, it can be a sign that something is wrong with the pregnancy. Low progesterone also can lead to miscarriage of an otherwise normal pregnancy, though this is preventable.
Female Hormones
The hormones estrogen and progesterone, both of which are critical to female menstrual cycles and reproductive function, overlap somewhat in their effects. You produce progesterone and estrogen each month as part of the normal menstrual cycle -- increasing progesterone levels around the time you ovulate causes the lining of the uterus to proliferate and thicken. This gives a fertilized egg somewhere to implant should conception take place during a given month.
Low Progesterone
Normally, about 14 days after you ovulate, your progesterone production falls off significantly, which results in sloughing of the uterine lining, or menstruation. This is not compatible with pregnancy: If you menstruate, a fertilized egg has nowhere to implant. As such, signals from a fertilized egg generally maintain your body's production of progesterone, thereby maintaining the lining of the uterus. The uterine lining serves as the source of nutrients and oxygen for a developing embryo until the third or fourth month of pregnancy.
Time Frame
Whether low progesterone should be a concern at two weeks pregnant depends somewhat on how you're counting. Technically, pregnancy dates from the first day of your last menstrual period, explain Heidi Murkoff and Sharon Mazel in their book "What To Expect When You're Expecting." As such, at two weeks pregnant, you've just conceived and your progesterone levels shouldn't be particularly high. If you have low progesterone at two weeks past conception -- which is technically four weeks pregnant -- it can signal a problem or potential problem with the pregnancy.
Ectopic Pregnancy
There are several possible causes of low progesterone during pregnancy. One possible cause is that the fertilized egg has implanted abnormally, in a location other than the uterine lining. This is called an ectopic, or tubal, pregnancy, notes the Advanced Fertility Institute of Chicago. A low progesterone level -- less than 15 ng/mL -- can indicate ectopic pregnancy. Your obstetrician will confirm this diagnosis with ultrasound. Unfortunately, ectopic pregnancies aren't viable.
Normal Pregnancy
Some women have low progesterone levels during otherwise normal pregnancies. If an embryo has embedded properly and progesterone is low nevertheless, your obstetrician might be able to use progesterone supplementation by injection or with pills to boost your progesterone levels. Very low progesterone -- again, less than 15 ng/mL -- can increase the risk of spontaneous abortion, or loss of the pregnancy. Supplementation can help, explains Dr. Miriam Stoppard in her book "Conception, Pregnancy and Birth."
References
- "What to Expect When You're Expecting"; Heidi Murkoff and Sharon Mazel; 2008
- Advanced Fertility Center of Chicago: Progesterone Levels
- "Conception, Pregnancy and Birth"; Miriam Stoppard, M.D.; 2008
