Obstetric prognosis in sisters of preeclamptic women – implications for genetic linkage studies

BACKGROUND: To investigate obstetric prognosis in sisters of preeclamptic women. METHODS: We identified consecutive 635 sib pairs from the Birth Registry data of Kuopio University Hospital who had their first delivery between January 1989 and December 1999 in our institution. Of these, in 530 pairs both sisters had non-preeclamptic pregnancies (the reference group), in 63 pairs one of the sisters had preeclampsia and the unaffected sisters were studied (study group I). In 42 pairs both sister's first delivery was affected (study group II). Pregnancy outcome measures in these groups were compared. RESULTS: Unaffected sisters of the index patients had uncompromised fetal growth in their pregnancies, and overall, as good obstetric outcomes as in the reference group. The data on affected sisters of the index patients showed an increased prematurity rate, and increased incidences of low birth weight and small-for-gestational age infants, as expected. CONCLUSION: Unaffected sisters of the index patients had no signs of utero-placental insufficiency and they were at low risk with regard to adverse obstetric outcome, whereas affected sisters were high-risk. Clinically, affected versus unaffected status appears to be clear-cut in first-degree relatives regardless of their genetic susceptibility and unaffected sisters do not need special antepartum surveillance.