Review of ethanol dispersion, distribution, and elimination from the fetal compartment

Abstract

This study is a review of alcohol dispersion into and elimination from the fetal compartment. PubMed searches were conducted for all years and all languages for relevant papers. We also hand searched the reference list of papers and text books for additional references. Alcohol concentration is determined by body water (49% for women), grams of ethanol consumed, and duration of drinking. The fetus has very limited metabolic capacity and transfer from the fetal compartment to maternal circulation is the major pathway to reduce fetal exposure. Vasoconstriction of the placenta-umbilical unit from alcohol and smoking decreases rates of alcohol elimination from the fetal compartment. By 20 weeks of gestation, keratinization of fetal skin reduces the permeability of fetal skin to very low levels, increasing the duration of fetal exposure and complicating alcohol elimination from the fetal compartment. Two reabsorption pathways, the intramembranous pathway and fetal swallowing, create a recycling system where much of the ethanol the fetus excretes will be reabsorbed back into its circulatory system. Fetal re-excretion of ethanol into the amniotic fluid occurs by means of fetal urine, breathing movements, and nasal excretions. Amniotic fluid then functions as a reservoir for ethanol, prolonging fetal exposure. While the fetus has the ability to metabolize some ethanol, removal from the fetal-maternal unit relies primarily on maternal metabolic capacity. The alcohol elimination rate from the fetal compartment is approximately 3% to 4% of the maternal rate. We conclude with examples of the clinical relevance of information from this review. .