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OP19.03: The use of transvaginal ultrasonography to predict preterm birth in women with a history of spontaneous preterm birth

Objectives: To establish the relationship between PAPP-A and β-hCG and low birth weight (< 2500 g) and preterm delivery (< 32 weeks) in a consecutive cohort of 1867 low-risk singleton pregnancies with a liveborn child. Methods: A cohort study including 1867 pregnancies undergoing first-trimester combined screening for Down syndrome in an 18-month period at a single center in Region Zealand, Denmark. Ultrasound data were combined with biochemical parameters, prenatal registry and PKU registry at Statens Serum Institut, Copenhagen. Results: There was a significant relationship between low PAPP-A and both low birth weight and preterm delivery. Using a PAPP-A cut-off of 0.64 MoM the sensitivity for detecting pregnancies with a birth weight < 2500 g was 31%, with a specificity of 84%. The positive predictive value (PPV) was 7% and the negative predictive value (NPV) was 97%. The relative risk (RR) for low birth weight associated with low PAPP-A was 2.18 (95% CI, 1.34–3.54). Using the 0.64 MoM PAPP-A cut-off the sensitivity for preterm delivery was 60%, the specificity 85%, the PPV 1.9% and the NPV 99.8%. The RR was 8.24 (95% CI, 1.39–48.9). Using β-hCG with a cut-off of 0.3 MoM, the sensitivity of low β-hCG for low birth weight was 7%, the specificity was 99%, the PPV 22% and the NPV 96%. The RR was 5.98 (95% CI: 2.66–13.45). Using a cut-off of 0.5 MoM the sensitivity of low β-hCG for preterm delivery was 40%, the specificity 91%, the PPV 2% and the NPV 99.7%. The RR was 6.87 (95% CI, 1.16–40.57). Conclusions: Low PAPP-A and β-hCG MoM values exhibited a significant correlation with low birth weight and preterm delivery in a consecutive cohort of low-risk pregnancies. The PPV was low making both markers unsuitable for screening. However, a combination of the markers, the likelihood ratio based screening for chromosomal abnormalities, and the use of additional markers could make screening for adverse pregnancy outcome a possibility.