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

Clinical Overview 

Amoxicillin, alone or with clavulanic acid (ACA), is widely used in pregnancy for the treatment or prophylaxis of infections. Due to pregnancy-induced changes in the pharmacokinetics of certain drugs, dose adjustments may be necessary to maintain effective antibiotic concentrations during pregnancy.  

Pharmacokinetics of amoxicillin in pregnancy

Pregnancy increases renal clearance and the volume of distribution, leading to lower amoxicillin concentrations in the blood of pregnant patients compared with non-pregnant adults. Pharmacokinetic studies and modelling confirm that amoxicillin concentrations are reduced by 15-25% during the second and third trimester.   The placental transfer of amoxicillin seems to be variable between patients. Based on placental-perfusion experiments, the placental transfer of amoxicillin is approximately 30%. 

Efficacy and safety of amoxicillin in pregnancy

Amoxicillin remains clinically effective in pregnancy, but no studies in pregnant patients have been conducted to demonstrate dose-related efficacy. Safety data are extensive and reassuring, with no consistent increase in congenital malformations. A small number of studies suggest a possible link with orofacial clefts after first-trimester use, though this has not been confirmed. For ACA, overall safety evidence is also reassuring, but one study suggested an association with neonatal necrotising enterocolitis after prophylactic use in preterm pre-labour rupture of membranes, a finding not replicated in later, smaller studies. No dose-response relationship was found between the daily dose of amoxicillin or ACA in the first trimester and major malformations. The dose-related safety has not been studied in the second or third trimester of pregnancy.

Conclusion 

Pregnancy increases renal clearance of amoxicillin, lowering maternal exposure, while placental transfer is moderate. Overall safety evidence for amoxicillin and ACA is reassuring, but dose-related efficacy and safety remain poorly defined.