Context. It has been proposed that preeclampsia may result from of an imbalance in angiogenic factors. Although prolactin (PRL) is mainly related to lactation, it is also involved in other biological functions, including angiogenesis.

Objective. To determine the relationship among preeclampsia, serum and urinary PRL levels, and excretion of antiangiogenic PRL fragments in urine.

Study design. Employing a cross-sectional design, urinary and serum PRL levels and presence of PRL isoforms were determined in 546 pregnant women (207 healthy pregnant, 124 with gestational hypertension, 48 with mild preeclampsia, and 167 with severe preeclampsia).

Results. Urinary PRL concentrations were significantly (p<0.001) higher in preeclampsia [11.99 ng/mg creatinine] than in healthy pregnancy [0.20 ng/mg creatinine] and gestational hypertension [0.19 ng/mg creatinine], and were even higher in severe preeclampsia compared with mild preeclampsia [21.20 vs. 2.77 ng/mg creatinine, respectively (p<0.001)]. Antiangiogenic PRL fragments (14–16 kDa) were detected in 21.6% of urine samples from women with severe preeclampsia, but in none from other groups. Patients with HELLP syndrome and/or eclampsia, placental abruption, acute renal failure, and pulmonary edema exhibited highest urinary PRL concentrations (p0.028) and frequency of antiangiogenic PRL fragments in urine (p0.036). High serum PRL levels were associated to severe preeclampsia independently of gestational age, proteinuria, and prolactinuria (p=0.032).

Conclusions. Preeclampsia is characterized by increased urinary PRL excretion. Urinary PRL concentrations and its isoforms appear to be suitable markers to assess the severity of preeclampsia and occurrence of adverse outcomes. PRL and and/or its isoforms might be involved in the pathophysiology of preeclampsia.