In vivo investigation of placental transfer early in human pregnancy

The use of coelocentesis to study placental drug transfer in the first trim ester has required the adaptation of existing pharmacologic models to the c hanging anatomical structures present before and after 12 weeks of gestatio n. The biochemical properties of the coelomic and amniotic fluids are impor tant parameters in evaluating the pharmacokinetics of drugs and toxins in e arly pregnancy. In particular, the protein concentration and pH of these fl uids are significantly different and vary widely with gestational age. Thes e biochemical variations are less likely to influence the distribution of i nert substances such as inulin inside the first trimester conception caviti es than the distribution of drugs such as diazepam or propofol. This can ex plain why they are not all accumulating inside the exocoelomic cavity. It h as been demonstrated that the permeability of the placenta is greater in ea rly pregnancy than at term. Furthermore, because of the slow turn-over of t he coelomic fluid, substances such as nicotine to which the mother is chron ically exposed accumulate inside the exocoelomic cavity. This prolonged fet al exposure to tobacco carcinogens has important teratogenic implications a nd should be further explored. (C) 2000 Elsevier Science Ireland Ltd. All r ights reserved.