PREDICTING THE RISK OF PRETERM LABOR BY SECOND TRIMESTER MEASUREMENT OF MATERNAL α-FETOPROTEIN LEVELS AND A RISK FACTOR SCORING SYSTEM

Background: Preterm labor (delivery after 20 weeks and before 37 weeks of gestation) is the leading cause of prenatal mortality in developed countries. Many women who have preterm labor have abnormally high plasma levels of α-fetoprotein in early pregnancy.
Methods: This study was designed to evaluate the ability of this biochemical test and a clinical risk factor scoring system to prospectively discriminate pregnancies at high risk for preterm delivery. In nested case control study six-hundred women were studied prospectively from the early second trimester until delivery. There were sixty women in the study group (those with preterm delivery) and sixty women in the control group (those with term delivery).Aplasma level sample was collected during the second trimester, between 17 and 30 week's gestation. Then α-fetoprotein was determined in both groups.
Results: The mean AFP level was 196.75±151.48 IU/mL in the study group and 85.98±55.90 IU/mL in the control group, both of which were statistically significant (p<0.001). The mean infants age was 33.11±3.40 weeks in the study group and 38.83±0.86 weeks in the control group (p<0.001) and mean of birth weight was 1988±672.33 gr in the study group and 3241.50±405.98 gr in the control group (p<0.001). The risk factor scoring system was >10 in 17% of women in the study group and in 8% of women in the control group. The sensitivity, specificity, PPV and NPV of this test was 78%, 65%, 69.10 and 75% respectively. The accuracy of the test, LR+ and LR- were 71%, 2.24 and 0.333 respectively.
Conclusion: The combination of measurement of maternal serum AFP in the second trimester associated with a risk factor scoring system provides a more accurate indicator of the risk of preterm delivery and therefore may be of use in targeting prevention strategies.