First trimester maternal serum placental protein 13 levels in singleton vs. Twin pregnancies with and without severe pre-eclampsia

Aims: To determine first trimester maternal serum placental protein 13 (PP13) in singletons vs. Twins with and without severe preeclampsia (PE). Methods: Serum samples were prospectively collected at 8-14 weeks of gestation. PP13 was determined by solidphase immunoassay. Patients were recruited in community clinics throughout the country, and from the twin antenatal assessment clinic in Assaf Harofeh Medical Center, Zerifin, Israel. Demographics, medical, and pregnancy history were obtained at enrollment. Pregnancy outcome was collected after delivery. PP13 was compared by the Wilcoxon rank sum test. Results: In singletons, PP13 declined with maternal weight and was lower in in vitro fertilization. Levels were converted into multiples of the median (MoMs) accordingly. In twins, the median was 1.74 MoM (n 76) vs. 1.00 in singletons (n 676, P 0.0001). Among twins with severe PE (n 10), the median was 1.53 MoM vs. 1.74 in unaffected twins (P 0.10), and 2.26 (n 6) for mild PE (P 0.30). Among singletons with severe PE, the median was 0.44 MoM (n 26, P 0.0001), and for mild PE 0.62 (n 17, P 0.001). Conclusion: PP13 is higher in twins than singletons, corresponding to the larger placental mass. Among singletons with severe PE, levels were significantly reduced, however, among twins, only a non-significant tendency for a reduction was recorded, and warrants further investigation in a larger series.