FETAL LUNG GROWTH IN EXTRA-UTERINE PREGNANCY

Abstract

Several hundred cases of advanced abdominal pregnancy have been reported. Although 20-40% resulted in livebirths, only 50-70% of those survived the early neonatal period. The major cause of death is unknown and most infants have multiple deformities involving mainly the joints and skin. Using an animal model, we freed rat fetuses from the uterus without disturbing the placental implantation site. The fetuses were allowed to reside in the peritoneal cavity, either within intact membranes (with amniotic fluid), or outside of the fetal membranes. Untouched littermate fetuses served as controls. The surgery was performed on either days 17, 18 or 19 of gestation and the outcome was analyzed at term (i.e. 2,3, or 4 days later). The fetuses were then killed, photographed and body, lung, liver, brain and placenta weights recorded. Total lung DNA was determined. Results: Extra-uterine fetuses with intact membranes were in all respects indistinguishable from littermate controls. Extra-uterine and extramembranous fetuses weighed slightly less than controls, all had thin, shiny skin with webs and contractures of multiple joints. After correction for body weight, only their lungs weighed significantly less (p<.01) and contained less DNA (p<.02). Lung DNA per gram of fetal weight was less (p<.05). The difference was even more significant following surgery on days 17 and 18. This animal model highlights the protective role of the amniotic environment and suggests that lung hypoplasia is a major cause of neonatal death in human abdominal pregnancy.