The full, clinically endorsed recommendation should be obtained from Lareb [link].   

Clinical Overview  

Labetalol is one of the preferred drugs for the treatment of hypertension in pregnancy. Because pregnancy alters the activity of drug metabolizing enzymes and foetal exposure occurs, dose-adjustments may be necessary to maintain effective concentrations during pregnancy.  

Pharmacokinetics of labetalol in pregnancy 

Pregnancy lowers maternal labetalol exposure. Studies report increased clearance of labetalol from mid-pregnancy onwards, with shorter half-life and lower plasma levels than in non-pregnant adults. Labetalol crosses the placenta, reaching cord concentrations that are typically about 50-60% of maternal levels.  

Efficacy and safety of labetalol in pregnancy 

Labetalol effectively treats antenatal hypertension in routine care, but dose-related efficacy has not been investigated in pregnancy. Safety evidence suggests no overall increase in congenital malformations. In late pregnancy, pharmacological effects on the neonate, such as hypoglycaemia, bradycardia and hypotension, are reported. Some studies indicate higher rates of small-for-gestational-age with higher maternal doses, but confounding by disease severity is likely. Compared to other beta-blockers, labetalol generally shows a comparatively favourable neonatal risk profile. 

Conclusion  

Maternal exposure to labetalol is reduced during pregnancy and foetal exposure is proportional to maternal levels. Dose-related safety signals exist but are likely confounded.