• Tippawan Liabsuetrakul and Krantarat Peeyananjarassri.
• Epidemiology Unit, Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla, Thailand, 90110.
• Cochrane Db Syst Rev. 2018 Aug 10; 8: CD008019.

BackgroundDuring elective (planned) caesarean sections, some obstetricians routinely dilate the cervix intraoperatively, using sponge forceps, a finger, or other instruments, because the cervix of women not in labour may not be dilated, and this may cause obstruction of blood or lochia drainage. However, mechanical cervical dilatation during caesarean section may result in contamination by vaginal micro-organisms during dilatation, and increase the risk of infection or cervical trauma.ObjectivesTo determine the effects of mechanical dilatation of the cervix during elective caesarean section on postoperative morbidity.Search MethodsWe searched the Cochrane Pregnancy and Childbirth Group's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) and reference lists of retrieved studies on 20 September 2017.Selection CriteriaWe included all randomised, quasi-randomised, and cluster-randomised controlled trials comparing intraoperative cervical dilatation using a finger, sponge forceps, or other instruments during elective caesarean section versus no mechanical dilatation.Data Collection And AnalysisTwo review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. We assessed the quality of the evidence using the GRADE approach.Main ResultsWe included eight studies with a total of 2227 women undergoing elective caesarean section. Of these, 1097 underwent intraoperative cervical dilatation with a double-gloved index finger or Hegar dilator inserted into the cervical canal to dilate, and 1130 did not undergo intraoperative cervical dilatation. Six of the eight included trials had high risk of bias for some of the risk of bias domains.Very low-quality evidence suggested it was unclear whether cervical dilatation had any impact on postpartum haemorrhage (estimated blood loss greater than 1000 mL; risk ratio (RR) 1.97, 95% confidence interval (CI) 0.48 to 8.13; 5/205 versus 3/242; one study, 447 women).Low- or very low-quality evidence showed no clear difference for the need for blood transfusion (RR 3.54, 95% CI 0.37 to 33.79; two studies, 847 women); postoperative haemoglobin (mean difference (MD -0.05, 95% CI -0.15 to 0.06; three studies, 749 women), or haematocrit (MD 0.01%, 95% CI -0.18 to 0.20; one study, 400 women); the incidence of drop from baseline haemoglobin above 0.5 g/dL (RR 0.92, 95% CI 0.64 to 1.31; two studies, 722 women), or amount of haemoglobin drop (MD -0.01 g/dL, 95% -0.14 to 0.13; three studies, 796 women); the incidence of secondary postpartum haemorrhage within six weeks (RR 1.18, 95% CI 0.07 to 18.76; one study, 447 women); febrile morbidity (RR 1.18, 95% CI 0.76 to 1.85; seven studies, 2126 women); endometritis (RR 0.94, 95% CI 0.35 to 2.52; four studies, 1536 women); or uterine subinvolution (RR 0.34, 95% CI 0.08 to 1.36; two studies, 654 women); the results crossed the line of no effect for all of the outcomes. There were no data for cervical trauma.We found a slight improvement with mechanical dilatation for these secondary outcomes, not prespecified in the protocol: mean blood loss, endometrial cavity thickness, retained products of conception, distortion of uterine incision, and healing ratio. The evidence for these outcomes was based on one or two studies. Cervical dilatation did not have a clear effect on these secondary outcomes, not prespecified in the protocol: wound infection, urinary tract infection, operative time, infectious morbidity, and integrity of uterine scar.Authors' ConclusionsAt this time, the evidence does not support or refute the use of mechanical dilatation of the cervix during elective caesarean section for reducing postoperative morbidity.Further large, well-designed studies are required to compare the effect of intraoperative mechanical dilatation of the cervix with no intraoperative mechanical cervical dilatation for reducing postoperative morbidity.

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