Answer:
Some of the fetus's blood vessels are contained in tiny hairlike projections (villi) of the placenta that extend into the wall of the uterus. The mother's blood passes through the space surrounding the villi (intervillous space). Only a thin membrane (placental membrane) separates the mother's blood in the intervillous space from the fetus's blood in the villi. Drugs in the mother's blood can cross this membrane into blood vessels in the villi and pass through the umbilical cord to the fetus.
Here's how a drug affects a fetus:
- The fetus's stage of development
- The strength and dose of the drug
- The genetic make-up of the mother, which affects how much of the drug is active and available
- Other factors related to the mother
Hope this helps and have a nice day!