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Many fetal deaths from placental insufficiency may be prevented by determining urinary estriol levels during the last trimester of pregnancy.
Kaighn Smith, MD, said that such measurements improve survival rate in two ways:
With rapidly falling estriol levels which are indicative of fetal distress, the clinician may be able to recognize intrauterine jeopardy earlier than otherwise indicated. He then may induce labor or perform cesarean section immediately to reduce the number of perinatal losses.
On the other hand, if estriol levels remain normal in a pregnancy complicated by factors leading to placental insufficiency, the fetus may be allowed to continue closer to term—thus obviating the danger of neonatal death due to prematurity.
These conclusions were based on studies of more than 900 complicated pregnancies at the University of Pennsylvania. They showed that the mortality (average of neonatal deaths and stillbirths) from pregnancies complicated by hypertension and/or toxemia dropped
Estriol: Forecasting Fetal Survival. JAMA. 1966;197(4):37. doi:10.1001/jama.1966.03110040023008