LISBON (FRONTLINE MEDICAL NEWS) – Dilation and curettage increases the risk for prematurity in subsequent pregnancy, according to a systematic review and meta-analysis of nearly 2 million women.

Overall, D&C for first-trimester miscarriage or pregnancy termination increased the risk for preterm birth (< 37 weeks) by 29% (Odds ratio, 1.29; 95% confidence interval 1.17-1.42).

Subgroup and sensitivity analyses performed to test the robustness of the finding showed D&C upped the risk for very preterm birth (< 32 weeks) by 69% (OR, 1.69; C.I. 1.20-2.38) and critical preterm birth (< 28 weeks) by 68% (OR, 1.68; C.I. 1.47-1.92).

A dose-response relationship was also identified, with multiple D&C procedures raising the risk of preterm birth even higher (OR, 1.74; C.I. 1.10-2.76), Dr. Marike Lemmers reported at the annual meeting of the European Society of Human Reproduction and Embryology.

“This really questions the use of dilation and curettage as first-line treatment for women with a miscarriage or termination of pregnancy since other treatment options are non-invasive, safe, well-tolerated, cheap, and accessible,” Dr. Lemmers, of the Academic Medical Center, Amsterdam, the Netherlands, said.

The increasing popularity of misoprostol as an alternative to D&C or for cervical priming prior to curettage would suggest that D&C use is declining. Still, gynecologists in the Netherlands treat half of all miscarriages with D&C, a figure that likely reflects practice elsewhere, Dr. Willem Ankum, the principal investigator, said during a press briefing.

The authors hypothesize that the mechanism behind the increased risk from D&C is that dilation may damage the cervix and affect cervical tightness or may damage the endometrial lining, leading to a malpresentation.

The systematic review and meta-analysis included 21 studies (7 prospective cohort studies, 11 retrospective cohort studies, and 3 case-control studies) involving 66,003 women with a history of D&C for first trimester miscarriage or termination, and 1,781,786 controls with a medically managed miscarriage or termination or no such events. The quality of the studies varied from 7 to 29 based on the Strobe score.

The primary outcome of risk of preterm birth was significantly increased with D&C regardless of whether the analysis relied only on the prospective studies (OR, 1.28; C.I. 1.01-1.60), retrospective studies (OR, 1.27; C.I. 1.12-1.45), or case-control studies (OR, 1.44; C.I. 1.18-1.77), Dr. Lemmers said.

Several audience members questioned the inclusion of older trials dating back to the late 1970s before prostoglandins had been introduced for cycle priming. One attendee cited a recent Scottish cohort study showing a declining preterm birth rate in women with previous miscarriage, possibly attributable to the increasing use of misoprostol (Cytotec) for miscarriage or termination and cervical priming before D&C (PLoS. Med. 2013; 10: e1001481 [ doi:10.1371/journal.pmed.1001481 ]).

Dr. Lemmers was aware of the Scottish study and said a funnel plot they performed showed “the exact same results” between older and newer studies. Further, a subgroup analysis of 38,905 women from studies dating from 1999 forward also showed an increased risk of preterm birth with D&C versus medical treatment (OR, 1.19; C.I. 1.10-1.28).

She added that it’s unlikely that the use of hysteroscopy with minimal dilation before in-vitro fertilization impacted results, but that outcomes may differ between women with a miscarriage versus termination of an attached pregnancy, although this calculation wasn’t possible based on the available data.

ZonMw, a Dutch organization for health research and development, funded the study. Dr. Lemmers and Dr. Ankum reported having no financial conflicts.

On Twitter @pwendl