Primary cesarean section and subsequent fertility.

The incidence of infertility after primary cesarean section (study group) was compared to an age- and parity-matched control group who underwent vaginal delivery during 1978 at The New York Hospital. Secondary infertility occurred in 17/291 (5.8%) of the study group and 5/279 (1.8%) of the control group (p less than 0.03). Excluding those who practiced contraception and those who underwent sterilization, this difference is still significant (p less than 0.02). Excluding those patients with a history of infertility prior to the 1978 birth, there was still a trend to increased subsequent infertility in the cesarean section group although this difference did not reach statistical significance (p less than 0.06). The patients with infertility did not have a higher incidence of postpartum endomyometritis, prolonged rupture of the membranes, or abnormal placentation. The causes of the secondary infertility could not always be directly related to cesarean section; the concept of an "infertility threshold" will be discussed.