Hypothesis: high levels of maternal adrenal androgens are a major cause of miscarriage and other forms of reproductive suboptimality.

A cause is proposed for several forms of reproductive suboptimality (viz foetal loss, preterm birth and low birth weight). The point is illustrated here in the case of miscarriage. I suggest that all these forms of reproductive suboptimality are partially caused by high levels of stress-related maternal adrenal androgens. The argument is supported by both experimental and epidemiological data.