The mechanism causing low urinary and serum total estriol (E3) levels in 3 pregnancies following colectomy was investigated by 1) measurement of unconjugated and total E, concentrations in maternal serum, stool, and urine; 2) assessment of placental function by the dehydro-epiandrosterone sulfate (DS) loading test; and 3) measurement of umbilical-serum total E3, dehydroepiandrosterone (D), and DS concentrations at the time of delivery. In the patients without colons the enterohepatic circulation of E3 was disrupted, hydrolysis and reabsorption of E3 in the gut did not take place, and excessive loss of conjugated E3 in the stool with consequent reduction of urinary and serum total E3 was consistently observed. Fetoplacental well-being was, however, suggested by the findings of normal levels of maternal-serum unconjugated E3, normal rise of maternal-plasma estradiol levels following DS infusion, ultrasonographic evidence of normal fetal growth rate, normal concentrations of umbilical-serum DS, D, and total E3, and no signs of fetal distress at delivery. It is concluded that, in pregnancies after colectomy, levels of maternal serum unconjugated E3, but not serum total E3 or urinary E3, should be used to monitor the fetoplacental function, and that subnormal urinary and/or serum total E3 levels in such patients may not reflect fetal jeopardy but rather reflect alteration in the E3 disposal mechanism.
© 1979 The American College of Obstetricians and Gynecologists