Benefits of Ultrasonic Screening of a Pregnant Population

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Abstract
The present study describes the evolution over a 5‐year period of an ultrasonic routine screening programme of a pregnant population with participation of approximately 90 % of the pregnant women. One obvious result obtained in the screening programme is the pronounced improvement of early detection of twins, the incidence now approaching 95 % with the mean gestational age for the detection being 20 (median 19) weeks. Early detection in combination with clinical measures was associated with a decrease in the incidence of twins born preterm (before week 37) from 33 % to 10 %. The perinatal mortality rate of twins fell from 6 to 0.6 % after the introduction of this programme.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 week), 95 % were delivered spontaneously within 12 days according to the estimates from the BPD, only 1.5 % being delivered later than the 42nd gestational week. The corresponding figures estimated from the last menstrual period was 79.3 % and 11.6 %.The experience gained from the programme recognized BPD for estimate of actual gestational age and the 17th gestational week was for practical reasons chosen for the first ultrasonic examination. As dating of the gestation is an important prerequisite in a screening programme for neural tube defect, the estimate of serum alphafetoprotein (AFP) was conveniently added to the ultrasonic screening programme. When ultrasound is used for exclusion of twins, dead fetuses, and erroneous dates, the percentage of amniocentesis occasioned by raised serum AFP value has hitherto been low (1.3 %).The introduction of ultrasound at our department has enabled us to reduce by 50 % the number of X‐ray examinations of pregnant women. The calculated cost for each examination made by midwives in our programme is Skr. 50:‐ (US $ 11).