IMPACT OF PRENATAL MID-TRIMESTER SCREENING ON THE PREVALENCE OF FETALSTRUCTURAL ANOMALIES - A PROSPECTIVE EPIDEMIOLOGIC-STUDY

The objective of this study was to evaluate the effectiveness of the m easurement of maternal serum alpha-fetoprotein (MSAFP) at 16 weeks and a subsequent routine ultra-sound screening at 18-20 weeks' gestation and the impact on the birth prevalence of congenital structural anomal ies in an unselected pregnant population of Hungary in a prospective e pidemiological study. A total of 63 794 pregnant women (representing o n-sixth of the population of Hungary) were offered this screening prog ram over 3 years (1988-90). Of the pregnant population, 75.7% (48 312) received MSAFP screening and in 81.0% (51 675), at least one ultrasou nd scan was performed. In the screened pregnancies, 496 craniospinal, thoracoabdominal, urogenital and other severe major anomalies occurred : 317 were detected at 18-20 weeks (sensitivity 63.1%; specificity 100 .0%; positive predictive value 100.0%). The sensitivity of ultrasound scanning was significantly higher (P<0.05) than of the MSAFP screening . (At the time of ultrasound scanning the MSAFP value was known.) In t his study, the less serious anomalies such as hydrocele, hypospadias a nd undescended testicle were not stystemically searched for, but the b irth prevalences were calculated. The overall mid-trimester prevalence of severe plus less severe major anomalies was 2.26%. The birth preva lences of severe major anomalies were 0.57 (craniospinal). 4.36 (thora coabdominal and urogenital) and 1.21 (other severe) per 1000. These va lues were lower than the mid-trimester prevalences which were 2.94 5.2 0 and 2.06 per 1000, respectively. The prevalence values at he age of 1 year were also calculated (0.36, 2.21, 0.54 per 1000 respectively). We conclude that our screening program with availability of terminatio n of pregnancy could significantly (P<0.05) reduce the prevalence of s evere major abnormalities at birth. Training programs in cardiac scann ing are required.