The etiology of preeclampsia is unknown. The relatively high risk of recurrence of preeclampsia in subsequent pregnancies to the same mother suggests a genetic basis for the disease, but the mode of inheritance is uncertain. We compare the risk of preeclampsia in second pregnancies for mothers whose first preeclamptic pregnancy was either a singleton or a twin pregnancy. The crude and adjusted recurrence risks of preeclampsia in twin and singleton pregnancies were estimated in a population-based register including the first and second pregnancies of 550218 women registered in the Medical Birth Registry of Norway, 1967-1998. The recurrence risk of preeclampsia in second pregnancy for women with a singleton pregnancy with preeclampsia the first time was 14.1% (95% CI: 13.6-14.6). For women with a first time twin pregnancy the recurrence risk was lower, 6.8% (CI: 4.3-10.1), P < 0.001. Thus, the crude excess risk for recurrent preeclampsia was 7.3% (95% CI: 4.5-10.0) in women with a first time singleton as compared to women with a first time twin pregnancy. The recurrence risk of preeclampsia is lower when the first pregnancy was a twin as compared to a singleton pregnancy. This observation is consistent with a polygenic liability model.
Copyright 2003 Wiley-Liss, Inc.