Artificial opening of the cervix during a planned caesarean section before the start of labour for reducing postoperative problems

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What is the issue?

The cervix is the narrow neck-like passage at the lower end of the uterus that enters into the vagina. A woman’s cervix is firm and undilated at the beginning of pregnancy, but progressively softens, all the way to term. The progressive opening, or dilatation, of the cervix occurs with uterine contractions during labour. Mechanical dilatation of the cervix at caesarean section, before onset of labour, is the artificial opening of the cervix. It is done by the surgeon, using a gloved finger, sponge forceps, or other surgical instruments.

Why is this important?

Some obstetricians believe that dilating the cervix helps the drainage of blood from the uterus, following birth by planned caesarean section before the onset of labour. Increased drainage may reduce the risk of intrauterine infection and postpartum haemorrhage. On the other hand, mechanically opening the cervix could result in contamination of the uterus with vaginal micro-organisms, and increase the risk of infections or cervical trauma. We set out to determine the effects of mechanical dilatation of the cervix during a planned caesarean section before the onset of labour on postoperative blood loss and uterine infection, when compared with no mechanical dilatation.

What evidence did we find?

We searched for evidence from randomised controlled trials in September 2017. We identified eight studies with a total of 2227 women undergoing elective (planned) caesarean section before the onset of labour. Of these women, 1097 underwent cervical dilatation with a double-gloved index finger, or in one study with a Hegar dilator, during surgery, while 1130 did not undergo cervical dilatation during surgery.

Low- or very low-quality evidence suggested it was unclear whether cervical dilatation had any impact on postpartum haemorrhage (estimated blood loss greater than 1000 mL), the need for blood transfusion, and other measures of blood loss, postpartum haemorrhage within six weeks, febrile morbidity (infection indicated by increased temperature over a defined time period), endometritis (infection of the lining of the womb), or uterine subinvolution (uterus not returning to its normal size after childbirth). There were no data for cervical trauma.

We found a slight improvement with mechanical dilatation for some outcomes that had not been specified in our original protocol, but the evidence for these outcomes was based on one or two studies (mean blood loss, endometrial cavity thickness, retained products of conception, distortion of uterine incision, and healing ratio). Cervical dilatation did not have a clear effect on other secondary outcomes, (again not specified in our original protocol): wound infection, urinary tract infection, operative time, infectious morbidity, and integrity of uterine scar.

What does this mean?

It is uncertain whether cervical dilatation has any impact on reducing postoperative problems after caesarean section. This means there is insufficient evidence to encourage or discourage the use of mechanical dilatation of the cervix at elective caesarean section for reducing postoperative ill-health.