Prophylactic antibiotics after instrumental birth?

What do we know about the use of prophylactic antibiotics after instrumental birth?

A large randomised controlled trial looking at the effect of antibiotics to prevent infection after operative vaginal birth has just been published in The Lancet (Knight et al 2019). Operative vaginal births include vacuum (ventouse) or forceps deliveries and, depending on where you live in the world, the rate of these varies from about 2% to about 15% of all births. As Berghella & Bellussi (2019) note in a related editorial, about 16% of the women who have this kind of birth end up with an infection.

“Compared with spontaneous vaginal delivery, operative vaginal delivery can introduce microorganisms into the genital tract, is associated with longer labour, more vaginal examinations, with bladder catheterisation before the procedure, and with more perineal lacerations and use of episiotomy, all of which can increase the risk of infections. These infections can occur even after discharge, and the risk peaks at about 6–7 days post partum.³ The incidence of infections is higher with forceps than with vacuum. Episiotomy also increases the risk of perineal infections compared with no episiotomy,⁴ possibly also because of the association with more and worse perineal lacerations.⁵ Unfortunately, the evidence on the effect of technical characteristics of the repair of perineal lacerations or episiotomies, or both, on perineal infections is scarce.⁶⁷ Perineal infections are associated with wound dehiscence, need for repair, and perineal pain, and influence women’s quality of life and sexual wellbeing.” (Berghella & Bellussi 2019).

So Knight et al (2019) set out to find out whether prophylactic (or preventative) antibiotics prevented maternal infection after operative vaginal birth. They recruited women from 27 hospitals and randomised them to either receive amoxicillin and clavulanic acid (1719 women) or a placebo (1708 women). As is always the case, a few women dropped out and some data were unavailable, so the numbers of women in each group in the results are slightly lower, but the results are clear:

“Significantly fewer women allocated to amoxicillin and clavulanic acid had a confirmed or suspected infection (180 [11%] of 1619) than women allocated to placebo (306 [19%] of 1606; risk ratio 0·58, 95% CI 0·49–0·69; p<0·0001).” (Knight et al 2019).

As you would expect, the occasional adverse event was experienced:

“One woman in the placebo group reported a skin rash and two women in the amoxicillin and clavulanic acid reported other allergic reactions, one of which was reported as a serious adverse event. Two other serious adverse events were reported, neither was considered causally related to the treatment.” (Knight et al 2019).

And the results have been greeted as important and “practice-changing”:

“This trial shows benefit of a single dose of prophylactic antibiotic after operative vaginal birth and guidance from WHO and other national organisations should be changed to reflect this.” (Knight et al 2019).

There are a few elements of the study that will, I am sure, generate discussion. Although having antibiotics reduced a woman’s chance of getting an infection by half, it did not eradicate the risk of infection completely, and more than one in ten of the women who had antibiotics still got an infection (compared to about one in five of the women who had the placebo). The study also does not appear to have looked at some of the things that women report as being reasons that they wish to avoid antibiotics, such as gastro-intestinal effects or the effects that these might have on their baby through their breastmilk. The authors acknowledged that “The safety reporting window for this trial was from administration of intervention to 6 h post administration or discharge—whichever was sooner” and that “Non-serious adverse events were not routinely recorded because the intervention is a licensed product being given at a standard dose,” (Knight et al 2019) but these side effects are still of importance to women and need to be balanced with the advantages of antibiotics. Even if antibiotics become an accepted part of the package that is instrumental birth, there will no doubt be women who will not want to accept the offer of antibiotics after an instrumental birth because, for them, the disadvantages don’t outweigh the benefits.

It is important not to forget, however, that operative birth does carry a high chance of problems such as infection and women who have caesarean sections are already given prophylactic antibiotics because of the high chance of infection following this procedure. Perhaps this reminder of how very high the chance of infection is so high in instrumental birth is will serve to spur us on to implement those things that reduce the chance of this being deemed necessary in the first place.

Both the study itself and the related editorial are freely available.