Progesterone is an important hormone in a woman’s reproductive cycle. It is critical in maintaining the uterine lining so that an early pregnancy can grow normally. It is produced by the follicle (egg sac) that originally released the egg that fertilized and implanted in the uterus.
Before ovulation, progesterone is found in low levels in the blood. After ovulation, it rises quickly, reaching a peak about 1 week after ovulation (which is also usually 1 week before the next period is expected). Thus, for women who have regular 28 day cycles, ovulation typically occurs around cycle day 14, progesterone peaks around cycle day 21, and menses occur (if pregnancy has not happened) around cycle day 28/29. (Women with shorter or longer periods will have ovulation – and thus peak progesterone – occurring earlier or later.)
For a woman with fairly regular cycles, a progesterone level done approximately 1 week before expected menses can show if she ovulated (released an egg) in that particular cycle. A level greater than 3ng/ml indicates that ovulation has occurred.
A progesterone level drawn during a menstrual cycle is only good for indicating that ovulation has occurred. Though some providers feel that having a higher progesterone level (i.e. >10 ng/ml) is better, there is actually no good evidence that this indicates a better overall situation. The reason is because the progesterone hormone is secreted in pulses – thus, if a woman were to have 10 progesterone levels drawn in a single day, the levels may actually vary considerably.
A better evaluation of adequate progesterone production is to look at the number of days occurring between ovulation and the very next period. (Note: consider the day after a positive ovulation kit to be the likely day of ovulation.) If there are fewer than 12 days between ovulation and a menstrual period, this may be an indication of a progesterone problem – the so-called ‘luteal phase defect’. This can be treated easily with progesterone supplementation.
In summary, a progesterone level drawn during a menstrual cycle has only 1 benefit – to show that ovulation has occurred. We have other ways of detecting ovulation – even before it has occurred: ovulation kits and ultrasound monitoring. Because these methods also allow us to time intercourse or intrauterine insemination, we frequently don’t check progesterone levels during a menstrual cycle. With pregnancy, though, we will monitor your progesterone levels closely and supplement if needed!
Tags: fertility testing, implantation, luteal phase defect, ovulation, ovulation predictor kit, progesterone | Category: Texas Fertility Center |