ULTRASONOGRAPHIC SCANNING OF PLACENTAL THICKNESS AND THE PRENATAL-DIAGNOSIS OF HOMOZYGOUS ALPHA-THALASSEMIA-1 IN THE 2ND TRIMESTER

In order to evaluate the association between placental thickness (PT) and fetal homozygous alpha-thalassaemia 1 before the appearance of cla ssic ultrasound findings of haemoglobin (Hb) Part's hydrops fetalis, a total of 473 pregnancies were collected. The control group included 4 22 normal pregnancies with a gestational age from 14 to 23 weeks and t he study group included 51 affected fetuses in the same gestational pe riod. Fetal biparietal diameter (BPD) and PT were measured by high-res olution ultrasound. PT was evaluated against BPD. In the control group , the PT generally increased in parallel with the advancement of gesta tional age. All PT measurements in the study group were above the mean PT of their respective gestational week in the control group. Forty-s ix (90 per cent) of the pregnancies in the study group had PT larger t han the mean plus two standard deviations of the control group. This s tudy suggests that ultrasound measurement of PT may be a useful aid in the prenatal diagnosis of Hb Part's hydrops fetalis before its classi c findings become apparent in the late second trimester or third trime ster.