Pregnancy in the 20th century involves women of many age groups from early
teens to the fourth or fifth decade. Modern medicine and in vitro fertiliza
tion techniques have increased options for pregnancy and childbirth. Pregna
ncy is a dynamic state, and medical concerns may involve disorders of the f
etus and mother requiring medications and special nutrients. Therefore, dif
ferent techniques have been developed to evaluate the placental transfer of
drugs and nutrients using tissues and cells derived from human placenta. T
hese include (a) isolated tissues and cells to study placental transport, (
b) primary and malignant trophoblast cell cultures and (c) biophysical meth
ods for studying placental transport. Also, convenient study models have be
en developed to evaluate placental transfer of safe drugs in pregnant women
. Some of the drugs studied by these techniques and models include (a) anes
thetics and pain medications used during delivery, (b) antibiotics and anti
-bacterials used to cure infections, (c) drugs abused by pregnant women and
(d) nutrients required for proper fetal growth. Placental transfer and exc
hange mechanisms are complicated processes, and in vitro models reflect onl
y partially the equilibria that exist among mother, placenta and fetus. The
perfused cotyledon model is elegant and simple but gives only restricted i
nformation. Isolated placental tissues give useful information about the ph
armacological effects of drugs. Metabolic studies using human placental mod
els provide information on the metabolism of a drug during placental transf
er and accumulation of the drug or its metabolite in the placenta or fetal
circulation. Several studies on the transplacental passage of drugs exist b
ut many questions regarding the transfer of drugs between the maternal and
fetal circulations and clearance of drugs from fetal circulation have yet t
o be answered. This article reviews in vitro and in vivo methods for evalua
tion of transplacental transport of drugs and their current effectiveness t
o obtain clinically useful data. (C) 1999 Elsevier Science B.V. All rights
reserved.