Which gestational change can increase fetal exposure to lipophilic drugs?

Which gestational change can increase fetal exposure to lipophilic drugs?

• A. Decreased uterine perfusion
• B. Increased uterine perfusion and volume
• C. Decreased amniotic fluid
• D. Reduced placental transfer

Answer: (B)

Fetal exposure to lipophilic drugs rises when placental transfer increases, and that happens with greater uterine perfusion and placental capacity during pregnancy. Lipophilic drugs diffuse easily across the placenta because they dissolve in the lipid membranes of placental cells; when maternal blood flow to the uterus is higher and the placenta has more surface area and perfusion, more drug reaches the placental barrier and can diffuse into fetal circulation. In other words, the combination of increased uterine blood flow and a larger, more perfused placenta provides more opportunity for the drug to move from mother to fetus. Decreased uterine perfusion would limit transfer, and reduced placental transfer would directly lower fetal exposure. Amniotic fluid volume changes can influence exposure for some drugs via different pathways, but they are not the primary driver of increased exposure for lipophilic drugs.

Fetal exposure to lipophilic drugs rises when placental transfer increases, and that happens with greater uterine perfusion and placental capacity during pregnancy. Lipophilic drugs diffuse easily across the placenta because they dissolve in the lipid membranes of placental cells; when maternal blood flow to the uterus is higher and the placenta has more surface area and perfusion, more drug reaches the placental barrier and can diffuse into fetal circulation. In other words, the combination of increased uterine blood flow and a larger, more perfused placenta provides more opportunity for the drug to move from mother to fetus.

Decreased uterine perfusion would limit transfer, and reduced placental transfer would directly lower fetal exposure. Amniotic fluid volume changes can influence exposure for some drugs via different pathways, but they are not the primary driver of increased exposure for lipophilic drugs.