Raised maternal serum cystatin C: an early pregnancy marker for preeclampsia.

The balance between trophoblast cathepsin and decidual cystatin C expression is pivotal in physiological trophoblast development. Defective trophoblast invasion is characteristic of preeclampsia and may involve derangement of the cathepsin/cystatin C balance. We conducted a prospective nested case-control study of healthy women with singleton pregnancies in the first trimester of pregnancy. Maternal serum cystatin C concentrations in those subsequently developing preeclampsia (n = 30) were compared to controls with normal outcome (n = 90). The median cystatin C concentration in early pregnancy was significantly higher (P = .0001) in those who subsequently developed preeclampsia (median 0.65 mg/L) when compared to normal pregnancy (median 0.57 mg/L). Of the 30 women developing preeclampsia, 14 (47%) had cystatin C above the 80th centile (0.67 mg/L) for the controls. Maternal serum cystatin C concentrations in early pregnancy may be of value in identifying women at high risk of developing preeclampsia.