First-trimester uterine artery Doppler and spontaneous preterm delivery.

OBJECTIVES

To assess the relationship between first-trimester uterine artery Doppler measurements and spontaneous preterm delivery.

METHODS

This was a retrospective analysis of uterine artery Doppler findings at 11-14 weeks in 73 singleton pregnancies with spontaneous preterm labor and 2417 pregnancies delivered at term.

RESULTS

The uterine artery mean resistance index (RI) was 0.68 (coefficient of variation 19%) and 0.69 (17%) in the preterm and term delivery groups, respectively (P = 0.35). The mean pulsatility index (PI) was 1.42 (39%) and 1.42 (46%) in the term and preterm delivery groups, respectively (P = 0.95). Bilateral diastolic notches were present in 34% of preterm deliveries and 33% of controls (P = 0.84). Restricting the analysis to the 19 pregnancies with preterm delivery before 34 weeks of gestation, no significant difference from controls was observed for RI (mean 0.71, coefficient of variation 11%, P = 0.41), PI (mean 1.56, coefficient of variation 29%, P = 0.27) or the number of bilateral notches (42%, P = 0.41).

CONCLUSIONS

Despite pathological evidence suggesting that defective placentation is associated with spontaneous preterm delivery, first trimester uterine artery resistance, as assessed by Doppler ultrasound investigation, is not different in pregnancies subsequently complicated by preterm labor compared to pregnancies delivered at term. This finding may be explained by a late failure of trophoblast development in cases destined to deliver preterm.