Benefits of Ultrasonic Screening of a Pregnant Population

Abstract

A 5 yr ultrasonic routine screening program of a pregnant population with participation of .apprx. 90% of the pregnant women is described. A pronounced improvement in early detection of twins resulted, the incidence now approaching 95% with the mean gestational age for the detection being 20 (median 19) wk. Early detection in combination with clinical measures was associated with a decrease in the incidence of twins born preterm (before wk 37) from 33-10%. The perinatal mortality rate of twins fell from 6-0.6%. The power of an early measurement of the fetal biparietal diameter (BPD) to predict the date of confinement was high. Of 848 pregnant women with an early BPD measurement (96.5% were measured before the 21st gestational wk), 95% were delivered spontaneously within 12 days according to the estimates from the BPD, only 1.5% being delivered later than the 42nd gestational wk. The corresponding figures estimated from the last menstrual period were 79.3% and 11.6%. BPD was used for estimate of actual gestational age and the 17th gestational wk was chosen for the 1st ultrasonic examination. As dating of the gestation is an important prerequisite in a screening program for neural tube defect, the estimate of serum .alpha.-fetoprotein (AFP) was conveniently added to the ultrasonic screening program. When ultrasound was used for exclusion of twins, dead fetuses and erroneous dates, the percentage of amniocentesis occasioned by raised serum AFP value was low (1.3%). The introduction of ultrasound at this department enabled the reduction by 50% of the number of X-ray examinations of pregnant women, and the cost when examination was performed by midwives was low.