Dilatation and curettage increases the risk of subsequent preterm birth: a systematic review and meta-analysis.

STUDY QUESTION: Could dilatation and curettage (D&C), used in the treatment of miscarriage and termination of pregnancy, increase the risk of subsequent preterm birth?

SUMMARY ANSWER: A history of curettage in women is associated with an increased risk of preterm birth in a subsequent pregnancy compared with women without such history.

WHAT IS KNOWN ALREADY: D&C is one of the most frequently performed procedures in obstetrics and gynaecology. Apart from the acknowledged but relatively rare adverse effects, such as cervical tears, bleeding, infection, perforation of the uterus, bowel or bladder, or Asherman syndrome, D&C has been suggested to also lead to an increased risk of preterm birth in the subsequent pregnancy.

STUDY DESIGN, SIZE, DURATION: In the absence of randomized data, we conducted a systematic review and meta-analysis of cohort and case-control studies.

PARTICIPANTS/MATERIALS, SETTING, METHODS: We searched OVID MEDLINE and OVID EMBASE form inception until 21 May 2014. We selected cohort and case-control studies comparing subsequent preterm birth in women who had a D&C for first trimester miscarriage or termination of pregnancy and a control group of women without a history of D&C.

MAIN RESULTS AND THE ROLE OF CHANCE: We included 21 studies reporting on 1 853 017 women. In women with a history of D&C compared with those with no such history, the odds ratio (OR) for preterm birth <37 weeks was 1.29 (95% CI 1.17; 1.42), while for very preterm birth the ORs were 1.69 (95% CI 1.20; 2.38) for <32 weeks and 1.68 (95% CI 1.47; 1.92) for <28 weeks. The risk remained increased when the control group was limited to women with a medically managed miscarriage or induced abortion (OR 1.19, 95% CI 1.10; 1.28). For women with a history of multiple D&Cs compared with those with no D&C, the OR for preterm birth (<37 weeks) was 1.74 (95% CI 1.10; 2.76). For spontaneous preterm birth, the OR was 1.44 (95% CI 1.22; 1.69) for a history of D&C compared with no such history.

LIMITATIONS, REASONS FOR CAUTION: There were no randomized controlled trials comparing women with and without a history of D&C and subsequent preterm birth. As a consequence, confounding may be present since the included studies were either cohort or case-control studies, not all of which corrected the results for possible confounding factors.

WIDER IMPLICATIONS OF THE FINDINGS: This meta-analysis shows that D&C is associated with an increased risk of subsequent preterm birth. The increased risk in association with multiple D&Cs indicates a causal relationship. Despite the fact that confounding cannot be excluded, these data warrant caution in the use of D&C for miscarriage and termination of pregnancy, the more so since less invasive options are available.

STUDY FUNDING/COMPETING INTERESTS: This study was funded by ZonMw, a Dutch organization for Health Research and Development, project number 80-82310-97-12066.