The influence of oral contraceptive and progestational drugs upon the mechanical activity of the non-pregnant human uterus in vivo.

The influence of oral contraceptives and progestational agents upon the contractions of the nonpregnant human uterus in vivo was studied. The uterine activity of women taking Lyndiol Orgametrial and Duphaston was recorded via a small vinyl catheter filled with a heparine-saline solution and connected to an Elma 490 A pressure transducer and a Siemans 1-channel Compensograph inkwriter. Laborlike contractions were observed during menstruation. The contractions increased during the proliferative phase. A typical pattern of uterine contraction consisting of a high frequency and low intensity was observed during the ovulatory phase. The lowest pressure recordings between contractions in the ovulatory phase were lowered as the pattern came to resemble the premenstrual phase. Basal pressures often exceeded 20 mm Hg during the ovulatory phase. The typical ovulatory pattern was not observed during Lyndiol treatment; rather a premenstrual phase or laborlike pattern occurred. Patterns recorded during the postmenopausal state were similar to those obtained during contraceptive medication. The results support the hypothesis that gestagens may owe part of their effectiveness to a form of myometrial dysfunction.