Antenatal antibiotics: too much, too little, or just right?

As obstetricians, when faced with a potential antepartum infectious process, we must decide whether to treat the mother, the fetus, or both? Since the mid-20th century, the widespread availability and use of antibiotics has led to a dramatic reduction in illness and death from infectious diseases, with obstetric care not excepted. Current estimates have suggested that >40% of pregnant women will be given some type of antibiotic therapy immediately prior to delivery. However, despite the advent of modern antimicrobial treatments, maternal sepsis is still the third leading cause of maternal mortality in developed countries. It has been estimated that for every maternal death, approximately 50 women experience severe morbidity. The long-term effects of the current strategies to reduce short-term maternal and neonatal morbidities are less well recognised. So it begs the question, are we subjecting the mother–infant dyad to antibiotic exposure unnecessarily? In this issue of BJOG, Drs Ledger and Blaser raise trenchant points on the use of antibiotics during pregnancy. With a 10–30% incidence of maternal colonisation with group B streptococcus (GBS), and with 33% of women undergoing caesarean delivery (two of the most common indications for maternal intrapartum antibiotic prophylaxis), between 1.5 and 2.0 million women (and their infants) will be exposed to antibacterial agents annually. What have been the risks and the benefits? The deliberation over risk-factor versus universal screening, and then treating for maternal colonisation by GBS, was an arduous debate in the USA. This question is still contested in other parts of the world. Prior to the advent of maternal prophylaxis for GBS, the incidence of neonatal sepsis was 1.7 per 1000 births. With the recommendation of universal screening and antibiotic prophylaxis in 2002, the rates of GBS sepsis have diminished by 85% (0.26 per 1000 births). This approach results in almost 700 women (and their unborn infants) being exposed to antibiotics to prevent one case of early-onset GBS disease; however, if the decision is made to treat women who are colonised with intrapartum GBS, it has been demonstrated that the most beneficial strategy is to screen and treat. Most women (87%) who deliver at term and are colonised with GBS will receive antibiotic chemoprophylaxis. Currently, the majority of cases (61.4%) of infant GBS disease occur in term newborns born to women who test negative for GBS prior to delivery. A potential future solution might be rapid screening assays to detect maternal intrapartum GBS colonisation, which may optimise the real-time identification of GBS colonisation while simultaneously helping to minimise unnecessary antibiotic exposure. Unfortunately the clinical feasibility of these technologies still needs to be assessed. With the most common reason for missed intrapartum chemoprophylaxis in term pregnancies being delivery at <4 hours after admission to hospital (which is the optimal time period for GBS antibiotic prophylaxis), delaying the initiation of antibiotic therapy by even 1 hour will further increase the exposure to the at-risk infant. With over 1.2 million women having a caesarean delivery, even small decreases in infectious morbidity will have a substantial impact on maternal health and health care use. Surgical scoring systems, such as the National Nosocomial Infections Surveillance (NNIS) risk index, were developed to enable comparisons of wound infection rates between surgeons, among institutions, or across time. However, clinical studies using this risk index as a determinate to administer antibiotic prophylaxis are lacking. Limitations of the NNIS risk index have been noted. For caesarean deliveries the NNIS risk index did not use a multivariate model, and not all of the claimed risk factors are found to be so in multivariate analyses. Furthermore, the NNIS risk index does not stratify adequately