Differences in uterine artery blood flow and fetal growth between the early and late onset of pregnancy-induced hypertension.

Purpose: We continuously measured bilateral uterine artery (UA) blood flow and compared differences in UA blood flow to investigate the differences in pathophysiology between early- and late-onset pregnancy-induced hypertension (PIH) and the usefulness of continuous monitoring of UA blood flow for the prediction of early-onset PIH.
Methods: The subjects were 76 PIH patients. The mean pulsatility index of bilateral UA (UAPI), an early diastolic notch in the velocity waveform, and regression curves were retrospectively examined and compared between early- and late-onset groups and the groups with and without fetal growth restriction (FGR).
Results: Regression curves of the UAPI in the early-onset group persisted at +2.0 standard deviations or more from the second to third trimester, while the UAPI in the late-onset group stayed within the normal range. A significantly higher mean UAPI with a high frequency of an early diastolic notch was observed in the early-onset group compared with the late-onset group in all pregnancy trimesters. There was a significant difference in UA resistance between the mild and severe groups and between the FGR and non-FGR groups, but to a small extent compared with the onset period.
Conclusion: There was a difference in pathophysiology between early- and late-onset PIH. Continuous monitoring of UA blood flow might be useful for the prediction of early-onset PIH if high UA resistance has been observed.