The menstrual cycle is orchestrated by precise hormone levels, and any abnormality in these levels can decrease the chance of getting pregnant in any given month. Women with abnormal hormone levels may have no symptoms and may be unaware of hormonal problems until they try to get pregnant. Many hormonal problems require medical treatment to achieve pregnancy.
Estradiol Levels
Estradiol, the primary form of estrogen, helps determine fertility potential. Estradiol is measured between days two and four of the menstrual cycle, most commonly on day two or three. Normal estradiol levels range between 25 to 75 pica grams per milliliter (pg/ml) on day two or three; both lower and higher levels can indicate fertility problems. Very low estrogen levels may indicate ovarian failure or menopause, while high levels can indicate decreased ovarian reserve or a leftover cyst from the previous cycle, explains FertilityPlus.com. Either may interfere with the recruitment and development of a normal egg in a given month.
By midcycle, the time of ovulation, estradiol levels should rise to around 200 pg/ml per mature follicle. Women undergoing fertility treatment may have very high estradiol levels, in the thousands, if they are making a number of follicles. Lower estradiol levels per follicle sometimes occur in overweight women or women with poor egg quality.
Follicle Stimulating Hormone (FSH) Levels
Follicle stimulating hormone, or FSH, is an important indicator of fertility. Normal levels on day two or three are 9 milli-International Units per milliliter (mIU/ml). Levels between 9 and 11 mIU/ml indicate a slightly reduced ovarian reserve and may slightly reduce pregnancy chances. Levels between 11 and 15 mIU/ml indicate reduced live birth rates and poorer egg quality. Levels over 20 mIU/ml indicate premature ovarian failure and a low, but not impossible, chance of pregnancy.
FSH levels rise with age and the decrease in the number of viable eggs left in the ovary. Fertility treatments may induce ovulation in women with high FSH levels, especially in those younger than 40. Women over 45 with high FSH have a greatly reduced chance of getting pregnant.
Luteinizing Hormone Levels
Luteinizing hormone, or LH, must rise at midcycle or an egg will not be released from the ovary. LH, normally less than 7 mIU/ml at the beginning of the menstrual cycle, rises at midcycle to 20 mIU/ml or higher in response to high estradiol levels. The rising LH, called an LH surge, matures the developing egg and releases it from the follicle, so it can be fertilized. Women with polycystic ovary syndrome, or PCOS, may have a higher LH to FSH ratio than normal. LH may be double FSH on day two or three of the menstrual cycle.
Progesterone Levels
Progesterone, produced by the corpus luteum (the remnant of the follicle that contained an egg), maintains a normal pregnancy. Progesterone levels after ovulation should rise to over 15 nanograms per milliliter (ng/ml). Low progesterone levels may indicate a decreased chance of implantation. Progesterone levels at the start of the menstrual cycle should be less than 1.5 ng/ml; higher levels can decrease pregnancy rates.
