| Summary: | Objective: This study aims to determine the strength of relationship between pregnancy-associated plasma protein A (PAPP-A) concentrations, using a Thai-specific reference range, and rates of idiopathic preterm delivery.
Materials and methods: A retrospective cohort study was conducted on consecutive singleton pregnancies, undergoing first-trimester screening for fetal Down syndrome, between January 2007 and July 2012, at our network hospitals in the northern part of Thailand. The prospective database was assessed for the records with complete outcome information, including PAPP-A concentrations, gestational age at delivery, medical and obstetric complications, and fetal and pregnancy outcomes. Pregnancies with potential causes of preterm delivery were excluded. The recruited women were assigned to two groups; a group with normal PAPP-A levels (≥10th percentile) and a group with low PAPP-A levels (<10th percentile). The main outcome was the rate of idiopathic preterm births in the two groups.
Results: Of 6867 screened women, 3830 were available for analysis and 670 were excluded because of potential confounders. Of the remaining 3160, 302 had low PAPP-A levels and 2858 had normal PAPP-A levels. The rates of spontaneous preterm births at ≤36 weeks, ≤34 weeks, and ≤32 weeks of gestation were significantly higher in women with low PAPP-A levels (7.6% vs. 17.9%, 3.1% vs. 11.9%, and 2.2% vs. 11.9%, respectively), with a relative risk of 2.37, 3.79, and 5.41 for preterm birth, respectively.
Conclusion: A PAPP-A level of ≤10th percentile was significantly associated with an increased risk for idiopathic preterm birth. Therefore, pregnant women with low PAPP-A levels in the first trimester should be considered at a high risk of preterm delivery.
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