Significant decrease of maternal serum serotonin levels in singleton pregnancies complicated by the HELLP syndrome

The purpose of this study was to compare peripartum maternal and umbilical cord serum serotonin levels in singleton pregnancies complicated by the HELLP syndrome (hemolysis, elevated liver enzymes, low platelets) or by severe preeclampsia with those of appropriate controls. The study population comprised 14 primigravidae women with class 1 or 2 HELLP syndrome (platelet count < 50 000 or < 100 000/mm(3), elevated transaminase levels, evidence of hemolysis) and 17 women with severe preeclampsia (American College of Obstetricians and Gynecologists criteria). Serotonin was measured in maternal serum immediately before delivery and in umbilical cord serum by a highly sensitive I-125-radio-immunoassay. The control groups comprised 31 women who had uncomplicated deliveries at term (control group I) and another 31 at the gestational age matched to that of each patient (control group II), Maternal serum serotonin concentration was 59.5 +/- 36.1 ng/ml (mean +/- SD) in the HELLP group, versus 94.9 +/- 40.5 ng/ml in control group I (p = 0.043, U-test) and 88.7 +/- 29.4 ng/ml in control group II (p = 0.048). Levels in the preeclampsia group (51.6 +/- 32.2 ng/ml) were not different from those in the HELLP group but were equally decreased when compared to control groups I (p = 0.009) and II (p = 0.003). We have observed a similar depression of serum serotonin concentrations both in severe preeclampsia and in the HELLP syndrome, reflecting the decreased platelet content of serotonin. It is uncertain whether these changes may be causally involved in the pathogenesis of hypertensive disorders of pregnancy. Decreased serum serotonin concentration may serve as an additional marker for platelet activation in preeclampsia and in the HELLP syndrome.