Luteal deficiency not a persistent cause of infertility.

A mid-luteal serum progesterone measurement was made in 579 cycles from 159 infertile women with unexplained infertility and the results compared with those in 267 cycles from 58 normal controls. There were no significant differences between the two groups in terms of mean progesterone values (41 versus 44 nmol/l); incidence of defective cycles (progesterone less than 28 nmol/l: 17 versus 15%) or severely defective cycles (progesterone less than 14 nmol/l: 4 versus 3%); incidence of a clinical diagnosis of luteal deficiency (LD) (at least two out of three cycles defective: 13 versus 12%); or incidence of persistent LD (continuing into a second series of two to three cycles: 1.7 versus 4.9%). There were no differences related to age, previous pregnancy or duration of infertility. These findings suggest that defective cycles occur as a random phenomenon in infertility and no more often than in normal women, and a diagnosis of LD implying a persistent condition to explain prolonged infertility in women with normal menstrual cycles must be a rare entity and requires at least six cycles of investigation (or none!) before treatment is considered.