Prediction of preterm delivery by using uterine artery doppler velocimetry in patients with preterm labor symptoms

OBJECTIVE: The main objective of this study was to assess the efficiency of uterine artery Doppler velocimetry during uterine contraction and inertia (basal), in the prediction of preterm delivery in patients with preterm labor symptoms. Our second purpose was to determine the underlying pathophysiolgy by comparing the blood flow in the basal uterine artery, umbilical artery, fetal middle cerebral artery (MCA) and placental pathologies between the same patient group and the control group matched according to the properties and gestational weeks.METHOD: This was a prospective study performed at the Dokuz Eylul University Hospital from June 2010 to March 2011. 172 patients with singleton pregnancies betwen 24 and 35 weeks that presented with signs of preterm labor and 169 healthy pregnant women with correlative properties who admitted for routine pregnancy visits were recruited for the study. Patients showing preterm labor symptoms were examined with external tocodynamometer for uterine contractions and the cervical length was measured by transvaginal ultrasound. Digital examination was performed for evaluating cervical dilatation, cervical ripening and Bishop score. Tocodynamometer measurements and uterine artery Doppler velocimetry was carried out simultaneously during uterine inertia and uterine contractions. Basal uterine artery, umbilical artery and MCA blood flow were evaluated with Doppler ultrasonography for both patients having preterm labor signs and for the control group. Each patient followed until the birth and their gestational age at enrollment, gestational age at delivery, time interval between admission and delivery, delivery in 48 hours/7 days/ 14 days were recorded. These dependent variables were analyzed for uterine artery Doppler measurements during basal tonus and during contractions and also for known methods and then the results were compared to assess the predictive value of Doppler ultrasound evaluations. The placental pathologies were interpreted and the relationship between the Doppler findings and placental pathologies were investigated. Changes in the blood flow of fetal umbilical artery and middle cerebral artery (MCA) during preterm labor were evaluated.RESULTS: When basal uterine artery pulsatility index (PI) compared with the control group, it was defined that the patients who admitted with preterm labor signs had higher average values (p=0,000). During basal uterine tonus and contractions, uterine artery PI were significantly higher in patients who delivered in 48 hours (p=0,000 \ p=0,000), 7 days (p=0,001 \ p=0,000) and 14 days (p=0,001 \ p=0,000) than the patients who did not deliver. According to the delivery in 48 hours dependent variable evaluation, during uterine contractions, when uterine artery PI ? 1,93; sensitivity was %82,8 and specificity was %85,3, PPV (positive predictive value) was %53,3 and NPV (negative predictive value) was %96,1. When analyzed in consonance with the delivery in 7 days variable when uterine artery PI?1,32 during contraction sensivity was %81,6, specifity was %74,6, PPV was %47,7, and NPV was %93,5. When it was evaluated based on the patients who delivered in 14 days, when uterine artery PI?1,26 sensivity was %76,1, specifity was %73,8, PPV was %51,5, and NPV was %89,4. When all diagnostic methods were evaluated in the same way, it was determined that uterine artery PI during contraction (p= 0,000) and cervical length measurement (p=0,010) were predictors of preterm delivery independent from other methods. In patients with ?25mm cervical length and with uterine artery PI?1,93 during contraction, predictive value of the test was increasing especially for delivery within 48 hours (sensitivity: 87,0, specificity: %84,8, PPV %80,0, and NPV: %90,3). Patient groups with placental pathology had substantially higher results for both basal uterine artery PI (p= 0,001) and uterine artery PI during contractions (p= 0,011). Observations resembled that fetal MCA PI values were significantly lower in patients who delivered in 48 hours/7 days/ 14 days (p= 0,010 / p= 0,014 / p= 0,000).CONCLUSION: In patients showing preterm labor symptoms, uterine artery Doppler measurements during contractions was found to be highly effective when compared with commonly used methods in identifying pregnant women at risk for preterm delivery. With this study, it?s also shown that the placental vascular lesions prosecuted for preterm delivery were associated with antenatal Doppler blood flow. Furthermore, it?s also determined that in patients who admitted with preterm labor symptoms which resulted in preterm delivery, the fetuses showed brain sparing effect.KEY WORDS: Preterm delivery, uterine artery Doppler, cerebroplacental circulation, placental pathology.