Progesterone and Pregnancy: What Levels Are Optimal?
Conception
Obie Editorial Team
Progesterone is a steroid hormone initially secreted after ovulation by the corpus luteum, an area in the ovary that develops after ovulation. Prior to ovulation, progesterone levels are very low. They increase right after ovulation and reach levels above 10 ng/ml usually by 5-7 days after ovulation takes place. If you are not pregnant, progesterone levels usually decrease around the time of the next menstrual period bleeding.
Hormones are one of the many things that can affect your fertility. Test your fertility knowledge and see how much you know about getting pregnant. Take our new fertility quiz!
Before ovulation, progesterone is well below 10ng/ml and after ovulation, it is well above 10ng/ml. The time right after ovulation until the next menstrual period is called the “corpus luteum phase” or the “luteal phase.” During the luteal phase, the fertilized egg travels through the fallopian tube into the uterus where it implants usually 6-12 days after fertilization. The normal luteal phase lasts on average 14 days, and it can be anywhere from 12 to 17 days long.
Pregnancy cannot be diagnosed by testing progesterone levels. Only the presence of the pregnancy hormone hCG diagnoses a pregnancy.
Progesterone prepares the endometrium (the lining of the uterus) for implantation and possible pregnancy. It prevents contractions of the uterus and the development of a new follicle, and during pregnancy, it is produced by the placenta and maintains the pregnancy until birth. Of course, it is important to start prenatal vitamins well before trying to get pregnant to obtain maximum efficiency.
Progesterone levels normally rise during the first 36-38 weeks of the pregnancy, then fall towards the due date. Pregnancy cannot be diagnosed by testing progesterone levels. Only the presence of hCG the pregnancy hormone hCG diagnoses a pregnancy.
Progesterone levels are usually drawn about a week after presumed ovulation because they reach peak levels at that time. Drawing the blood too early may give false-negative test results. A false negative progesterone level result means that you did ovulate but the blood was drawn too early and the progesterone level was falsely low. After ovulation, progesterone is produced increasingly from the corpus luteum and the progesterone levels gradually rise from a baseline of 1.5 to 3 ng/mL by the first day after ovulation. Levels then continue to rise until it reaches a peak 7 days after ovulation reaching levels of approximately 10-20 ng/mL. Progesterone levels can vary depending on the timing of the blood draw, and even on the same day can be very different.
Progesterone levels are only averages and they can change based on many variables. For example, the timing of the cycle, whether you ovulate or not, which lab tested them, whether blood is taken after you eat or before, and whether it's in the morning or afternoon, can all affect the outcome of a progesterone level test.
A low progesterone level especially a level below 10 ng/ml may mean that you did not ovulate. If you did ovulate, there are many different opinions as to what to do if the levels are low. Some doctors give progesterone (pills, shots, suppositories) and others don't treat unless there has been some proof of pre-existing low progesterone in non-pregnancy cycles.
According to a study done by Buckley and colleagues (Ann Emerg Med 2000 Aug;36(2):95-100), all patients with ectopic pregnancy had a progesterone level below 22 ng/ml. Of the patients with a progesterone level below 22 ng/ml, 10% had an ectopic pregnancy, but none of the patients with progesterone over 22 had an ectopic pregnancy. Of the patients who did not have an ectopic pregnancy, 73% had a progesterone level below 22 ng/ml. This means that if your progesterone level is above 22 ng/ml, your chances of having an ectopic pregnancy according to this study was 2% or less. But even if your progesterone level is below 22 ng/ml, your chances of NOT having an ectopic is above 88%.
The two main reasons for an elevated progesterone level are ovulation and pregnancy. Other than after ovulation or pregnancy, progesterone levels can also be elevated by the following:
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There is no real agreement among doctors whether giving progesterone early in pregnancy will improve pregnancy outcome.
During pregnancy, hCG levels have clear patterns. Find out more about hCG and use our free hCG calculator.