Unmeasurable relaxin concentrations in repeated pregnancies after embryo transfer.

Unmeasurable serum relaxin concentrations were found in repeated serum samples taken during two subsequent pregnancies in a woman pregnant after in vitro fertilization in artificial cycles. Despite the absence of relaxin both pregnancies were carried out normally until term except for symptoms of pelvic girdle relaxation. Labour induction was attempted at term as placental insufficiency was suspected. However, the cervical score remained unfavourable and Cesarian section was performed. In the second pregnancy elective Cesarian section was performed due to mild preeclampsia. This case indicates that relaxin may not be important for either suppression of myometrial activity or pelvic girdle relaxation during human pregnancy.