Placental function, fetal distress, and the fetal/placental weight ratio in normal and gestotic pregnancies

The ratio between fetal and placental weight is often thought to be a measure of the reserve capacity of the placenta. The aim of our study was to investigate the relationship between 1) endocrinologic parameters during pregnancy (serum placental lactogen - HPL, urinary estriol - E3), 2) the occurrence of fetal distress during labor, and 3) the severity of EPH gestosis, and the fetal/placental weight ratio at various gestational ages. The data from a total of 4911 consecutive pregnancies and deliveries were evaluated. Up to 37 weeks the mean fetal/placental weight ratio was significantly lower in infants with fetal distress. Up to 32 weeks there was a positive correlation between the percentage of women with low HPL and E2 levels and the percentage of infants with fetal distress, and the gestosis index. In addition there was a significant increase in the mean fetal/placental weight ratio in the group with moderate and severe gestosis. With advancing gestational age fetal/placental weight ratios were independent of the severity of EPH gestosis. It is concluded that until 37 weeks fetal distress is associated with a significant lower fetal/placental weight ratio. The morphologic and functional changes in placentas of gestotic pregnancies do not manifest themselves in either an increase or a decrease of the mean fetal/placental weight ratio after 33 weeks.