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Emergence of late-onset placental dysfunction: relationship to the change in uterine artery blood flow resistance between the first and third trimesters.

OBJECTIVES
To test if emergence of third-trimester (T3) placental dysfunction is related to the impedance change in uterine artery blood flow resistance between the first trimester (T1) and T3.


STUDY DESIGN
Mean T1 and T3 uterine artery (mUtA) pulsatility index (PI) was measured in 1098 singletons. Each patient's individual mUtA-PI change was calculated ([(T3 PI - T1 PI/interval in days)] × 100; ΔmUtA-PI). This parameter and T1 and T3 mUtA-PI z-scores were related to placenta-related disease (PRD) and to constitutionally small neonates (CS).


RESULTS
Forty-seven (5%) women had PRD and 83 (8.7%) delivered a CS neonate. T1 and T3 mUtA-PI z-scores were higher with PRD (0.418 versus -0.097 and 1.06 versus -0.13, p < 0.001 for all). Change in mUtA-PI (ΔmUtA PI) was similar for patients with PRD. However, the prevalence of PRD doubled with rising ΔmUtA-PI (11.1% versus 5.2%, p = 0.041).


CONCLUSION
T3 uterine artery Doppler performs significantly better in detecting patients at risk for late-onset PRD than T1 or the gestational age change in uterine artery Doppler resistance This suggests that a proportion of late emerging PRD is not amenable to early screening by uterine artery Doppler. Further research is essential to identify the optimal screening strategy for late-onset placental dysfunction.