Poisoning in pregnancy and lactation

Introduction

• Physiological changes
  • Absorption – Delayed gastric emptying and intestinal transit time slow drug absorption and may prolong the period where decontamination is of benefit
  • Distribution– Increased blood volume (50%) increases Vd and decreases plasma levels; dilution of plasma proteins increases free drug levels though
  • Elimination – Renal blood flow and GFR increase
• Maternal drug levels are the most significant determinate of fetal exposure as most drugs cross the placenta by diffusion
  • Usually levels are the same but some have lower levels in fetus and some have higher levels (valproic acid and diazepam)

Introduction

• Most drug intoxications are managed as for non-pregnant women and excellent maternal care is the best predictor of good fetal outcome
• Fetal monitoring may be useful to detect fetal compromised
• Specific agents pose specific fetal risks including:
  • Carbon monoxide
  • Methaemoglobin-inducing agents
  • Lead
  • Salicylates

Follow-up

• If fetus survives, teratogenicity risk is low
• Theoretically, teratogenicity is more likely if intoxication occurs in first trimester and mother should be counselled about this
• Paracetamol OD treated with NAC has not been shown to be associated with any fetal abnormality even in the first trimester

Breastfeeding

• The decision to continue breastfeeding in the setting of acute poisoning involves a risk-benefit analysis
• Percentage of maternal dose of most drugs excreted in breast milk is around 2-3% and usually does not pose a poisoning risk
• Usually best to interrupt breast feeding until mother recovered, provided this can be done without compromising infant nutrition

Last Updated on October 14, 2020 by Andrew Crofton