[Diagnostic methods for fetal malformations in the first half of pregnancy]

Fetal abnormalities are the most common cause of perinatal and postnatal death and infant handicap. For this reason prenatal screening (for fetal malformation) has become a routine part of obstetric care in many countries. Most often used are biochemical tests and continuously developing ultrasound diagnostics which makes possible precise analysis of the fetal morphology. There is interesting to establish a noninvasive test for the early detection of fetal malformation in pregnancy which is based on ultrasound examination (NT measurement from the 10th to the 19th weeks, presence of nasal bone in the first trimester ultrasound), correlated with serum concentration of AFP, beta-HCG and oestriol in the second trimester of pregnancy (triple test). The main aim of the study was to establish a diagnostic schema for detection of fetal malformations based on NT measurement in the first and second trimester coupled with triple test performed in the second trimester.

A group of 775 pregnant women from the 10-th week of pregnancy until childbirth has been put under examination. Between the 10th and the 14th and than between 15th and 19th week of pregnancy ultrasound examination with fetal biometry and NT measurement was done. NT measurements have been performed in accordance with the standards worked out by professor K. Nicolaides. At the first ultrasound examination the presence of the nasal bone was observed. The next step was performing the triple test between the 15th and 19th week of pregnancy. On the same day as second ultrasound examination blood was taken to determine the results of the triple test (ELISA method). The obtained results have undergone statistical analysis.

The age of women qualified for the examination oscillated between 15 and 45 (over 35 -9.4%). There were 8 fetal malformations recognized all connected with the chromosomal anomalies, namely, 4 Downs syndrome, 2 fetuses with trisomy of the 18th pair of chromosomes and 2 with triploidy. At all physiologic pregnancies nasal bone was seen during first ultrasound examination. The obtained results of nuchal fold measurements and concentrations for the parameters of the triple test have been the basis to calculate medians in the particular weeks of pregnancy. In all the cases of genetic malformations the widening of the nuchal fold above 99 percentile (MoM NT) has been observed. Fetal nasal bone were absent in 62.5% first trimester ultrasound examinations. The risk of the occurrence of a genetic malformation resulting from the mother's age combined with the risk connected with the NT measurements and the results of the triple test for the cut-off point 1:250 (which seems to be the best for this population) gave 100% sensitivity, 0.6% % of false positive results and the positive predictive value of 80%. The above mentioned results are better than the ones which were obtained within the triple test only, where for the previously fixed cut-off point 1:250 sensitivity reached 63%, positive predictive value 25% and 4.4% false positive rate. Performing the so-called integrated test in which the risk of the occurrence of any malformation is estimated on the basis of the NT measurement in the first and the second term of pregnancy seems to be far more useful.

Diagnostic schema for detection of fetal malformations in the first half of pregnancy which is based on ultrasound examination (NT measurement from the 10th to the 19th weeks), correlated with serum concentration of AFP, beta-HCG and oestriol in the second trimester of pregnancy (triple test) is very sensitive and safe method of the prenatal diagnosis leading to significant decrease of the invasive procedures (amniocentesis).