The management of the cardiac patient in labour: primum non nocere

Cauldwell et al. discuss three aspects in the management of labour in pregnant women with cardiac disease, for which evidence is limited and most recommendations based on clinical experience. A few points require consideration, as expert opinions differ. Guidelines suggest that clinically stable patients with complex congenital heart disease should anticipate a normal labour and delivery and that the avoidance of Valsalva manoeuvres to minimise haemodynamic perturbations should be considered only in those with critical obstructive lesions, fragile aortas, pulmonary hypertension and when venous return or myocardial contractility is seriously compromised (Canobbio et al. Circulation 2017;135;doi:10. 1161/CIR.0000000000000458). Epidural analgesia enables suppression of the Valsalva reflex, allowing prolongation of the passive phase of the second stage of labour. This facilitates more spontaneous vaginal deliveries and the application of instruments at lower stations (Roberston et al. J Obstet Gynaecol Can 2012;34:812–9). High rates of instrumental deliveries in reported studies may suggest a more liberal use of instrumental deliveries than recommended and the erroneous notion of ‘elective shortening of the active phase’, which does not equate with prolongation of the passive phase. Despite liberal recourse to instrumental deliveries, Robertson et al. showed no increase in thirdor fourth-degree tears over matched controls (8/377 versus 29/766, P = 0.14). Higher reported perineal trauma rates could be due to regional variations or the general decline in proficiency with the use of forceps, or be a reflection of higher proportions of difficult, unplanned instrumental deliveries for obstetric indications compared with planned outlet deliveries to obviate maternal expulsive efforts. In patients with intravenous access, recommended active management of the third stage of labour includes a 10–40 U oxytocin infusion over 1– 4 hours (>0.16 U/minute). Intravenous boluses that are known to cause profound hypotension, resulting in cardiovascular collapse and death, are discouraged, especially in women with cardiac disease. The cited study that reports no adverse outcomes when a slow intravenous bolus (2 U/ 10 minute) was administered in addition to a ‘low-dose’ infusion (0.012 U/minute) is underpowered. While the optimal oxytocin dose remains debated, consideration should be given to using standard-dose oxytocin infusions instead of boluses. The suggestion that the ‘introduction of a policy’ on infective endocarditis (IE) prophylaxis in response to the 2011 European Society of Cardiology guidance is responsible for an increase in the rates of IE in the UK is contentious. The cited paper is a time-series analysis suggesting a temporal association—but no causal relation—between IE cases and prescribing patterns of dentists and family doctors for dental procedures, and does not address pregnant women with cardiac disease. Studies from the USA that examined trends following the change of American Heart Association IE guidelines (Desimone et al. Circulation 2012;126:60–4; Bikdeli et al. J Am Coll Cardiol 2013;62:2217– 26) found no increase in IE cases. Given the small risk of IE from obstetric procedures and documented implications of the change in vaginal microbiota with intrapartum antibiotics, decisions on IE prophylaxis are best individualised based on risk profiles and existing guidance. Although high-quality evidence on the management of labour in women with cardiac disease is lacking, the best possible outcomes can be ensured by adherence to existing evidence on oxytocin infusions and IE prophylaxis, restricting elective instrumental deliveries for cardiac indications and conducting these deliveries in centres that possess necessary expertise. When making alternative recommendations, we must ensure that we first do no harm.