In chronic hypertension, it is the Dopplers that predict preeclampsia

Design

secondary analysis of a prospective cohort with propensity score matching, one case to two controls

Population

1,258 singleton pregnancies with chronic hypertension undergoing routine ultrasound at 35+0 to 36+6 weeks; 167 cases with estimated fetal weight below the tenth percentile, 64 of them with abnormal Dopplers

Primary outcome

development of superimposed preeclampsia by traditional and current guideline definitions

Effect

preeclampsia in 234/1,258 (18.6%) overall; more frequent in growth-restricted cases than matched controls across all definitions, with delivery 1.7 weeks earlier; no difference for small fetuses with normal Dopplers

Whether a small fetus in a woman with chronic hypertension signals superimposed preeclampsia or is simply a complication of the hypertension has practical consequences for surveillance. This secondary analysis of a prospective cohort took 1,258 singleton pregnancies with chronic hypertension who had routine ultrasound at 35+0 to 36+6 weeks, and compared 167 cases with an estimated fetal weight below the tenth percentile against propensity-matched controls, splitting cases by whether Dopplers were abnormal.

Among the 1,258 women, 234 (18.6%) developed preeclampsia. Cases with fetal growth restriction — a small fetus plus abnormal uterine, umbilical or middle cerebral artery Dopplers, 64 women — more often developed preeclampsia by any definition, more often had induction and caesarean delivery, delivered 1.7 weeks earlier and more often had babies below the tenth percentile or admitted to the neonatal unit. Cases with a small fetus but normal Dopplers did not differ from controls in preeclampsia, though they delivered slightly earlier and had smaller babies.

The distinction is the finding, and it is directly actionable: a low estimated fetal weight at 35-36 weeks in a woman with chronic hypertension means something quite different depending on the Dopplers. Where they are abnormal, intensify maternal as well as fetal surveillance and expect earlier delivery. Where they are normal, the fetus is small but the maternal trajectory looks like anyone else's. This is a single secondary analysis at one gestational window, and the authors ask for replication earlier in pregnancy before it is generalised.

• Do the Dopplers before deciding what a small fetus means in chronic hypertension
• Abnormal Dopplers: step up maternal surveillance for preeclampsia, not only fetal monitoring
• Normal Dopplers with a small fetus did not raise preeclampsia risk above matched controls
• Expect delivery about 1.7 weeks earlier in the growth-restricted group and plan accordingly
• Findings apply to 35-36 weeks only; earlier gestations were not tested

The statistics, in plain English

Propensity score matching balanced measured characteristics — age, body mass index, parity, prior preeclampsia and others — and the reported standardised mean differences below 0.1 confirm it worked for those variables; it can do nothing about unmeasured ones. The growth-restricted group numbers 64 women, so the individual outcome comparisons rest on few events and the size of each difference is uncertain even where the direction is consistent. Preeclampsia was defined three different ways and the finding held across all three, which is more reassuring than any single definition would be.

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