A previous blog regarding AMH levels was greeted by more than 150 questions from interested readers. A common question was regarding the clinical significance of a low AMH level. I am young and my AMH level is low. What does this mean? Does a low AMH level mean I will never get pregnant?
Hagen et al. addressed this very question in a recent issue of the journal Fertility and Sterility (Low concentration of circulating antimullerian hormone is not predictive of reduced fecundability in young healthy women: a prospective cohort study Fertil Steril 2012; 98:1602-8). They followed a total of 186 young Danish couples that intended to discontinue contraception to become pregnant until they conceived or for six menstrual cycles. They calculated the fecundability ratio (FR) (i.e., the monthly probability of conceiving) and time to pregnancy (TTP) was measured as the number of cycles from stopping birth control to pregnancy. They measured AMH levels and anticipated that those with low AMH levels would have a low FR and take longer to conceive. AMH levels were measured and were divided into 3 groups low (quintile 1), medium (quintile 2 -4) and high (quintile 5). The results are interesting.
59% of couples conceived during the study period. There was no difference in the FR in women with low or medium AMH levels (FR 0.81; 95% CI 0.44 – 1.40)! In contrast women with high AMH levels had reduced FR (FR 0.62; 95% CI 0.39 – 0.99). High AMH levels are often seen in women with polycystic ovary syndrome (PCOS) and have irregular cycles. This decrease in FR was significant even when women with irregular menses were excluded from the analysis.
Very few of these women had very low AMH levels (<0.16 ng/mL). So the study cannot be used to reassure this group of patients. It is possible that even in young patients, very low AMH levels may indeed be associated with premature menopause.
In IVF-related literature, a low AMH level is useful as a marker of follicle quantity than egg quality. This study demonstrates that in the context of natural conception in young women, where only one egg is involved, low AMH level also does not reflect egg quality.
Women with high AMH levels and regular cycles had lower chance of conception. These women may be similar to the group often termed ovulatory PCOS. They have other hormonal imbalances (elevated circulating levels of testosterone) that may be responsible for the lower FR.
They conclude that low AMH levels in young healthy women do not seem to be a predictor of reduced fecundability. This is consistent with high egg quality in these young women, despite a reduced ovarian reserve. Conversely, women with high AMH levels had a 40% reduction in the FR, and this persisted even after exclusion of women with irregular cycles.
So what does all this mean? At present, routine measurement of AMH level as a “fertility check up” in young women is not useful. This study clearly shows that young women with low AMH levels did not have a decreased chance of conception compared to women with normal AMH levels.