Increased risk of preterm birth in women with cervical conization.

OBJECTIVE

To determine the relation between cervical conization and preterm birth.

METHODS

All Danish women with singleton pregnancies who gave birth to their first infant in 1982 and second infant during the time period 1982-1987 were included in a register-based cohort study. Information on pregnancy outcome and cervical conization in 1977-1987 was obtained from the Medical Birth Register and the National Register of Hospital Discharges.

RESULTS

In a cohort of 14,233 women, 170 had cervical conization. Thirty-four had cervical conization before the first delivery, 62 between the first and the second, and 74 after the second delivery. Women with cervical conization had a significantly higher risk of preterm birth. In addition, women with subsequent cervical conization had a higher risk of preterm birth in previous pregnancies. However, the risk of preterm birth was higher in women with previous than with subsequent cervical conization.

CONCLUSIONS

Cervical conization is correlated with preterm birth. Because women with subsequent cervical conization have an increased risk of preterm birth in preceding pregnancies, factors other than the surgical intervention may contribute to the significantly increased risk of preterm birth.