Essential thrombocythemia as a risk factor for stillbirth.

INTRODUCTION The risk of abortion is known to be high in women with essential thrombocythemia (ET). However, a few studies have focused on the risk of stillbirth among fetuses reaching gestational age compatible with life. METHODS Review of medical charts of pregnant women with ET who received cares at a single center between January 2003 and June 2013 and the English literature in which more than 20 pregnancies with ET were dealt with regarding outcomes. Outcomes were classified into three categories: spontaneous abortion or preterm delivery before GW 24, stillbirth at and after GW 24, and live birth (LB). Japan national statistics was used to estimate the risk of stillbirth among women with GW 22 or more. RESULTS In all nine pregnancies in four women with ET at our hospital, two miscarriages, one stillbirth (intrauterine death at GW 35), and six LBs occurred. There were six reports in the English literature in which a total of 374 pregnancy outcomes were described: 110 miscarriages (29%), 14 stillbirths (3.7% of all 374 pregnancies and 5.3% of 264 pregnancies with GW≥24), and 250 LBs (67%) occurred. Japan national statistics between 1995 and 2011 indicated that the risk of stillbirth was less than 0.50% among women with GW≥22. CONCLUSIONS The risk of stillbirth was extremely high among women with ET. More intensified monitoring of fetal wellbeing may be required to improve outcome of pregnancy complicated with ET.