IPM Take
Preeclampsia is usually defined through what is happening to the mother: rising blood pressure, proteinuria, organ dysfunction and the escalating risk that may force an early delivery.
But the fetus is experiencing the disease too.
A new prospective study suggests that severe preeclampsia is associated with measurable changes in how the fetal heart functions, potentially offering another window into the physiological strain created by placental disease.
The most interesting finding is not simply that fetal cardiac measurements differed between severe and non-severe preeclampsia. It is that some of those differences remained after researchers accounted for gestational age, maternal age, body mass index, early-onset disease and fetal growth restriction.
That makes the signal harder to dismiss as merely an artefact of smaller or more premature fetuses.
Still, this is not ready for clinical adoption.
The study was single-centre, observational and relatively small. Its analyses of how well individual cardiac measures distinguished severe disease were exploratory, and the same measures were substantially weaker at predicting which babies would require neonatal intensive care.
That gap matters.
A test that separates two research groups is not automatically a test that improves a clinical decision.
For now, fetal cardiac indices such as the Tei index and isovolumetric relaxation time are better understood as signals of fetal cardiovascular adaptation, not validated tools for deciding when to deliver or which pregnancy needs escalation.
The research question is now whether that physiological information can add something meaningful to the surveillance tools clinicians already use.
Executive Summary
A prospective observational study published in Scientific Reports examined fetal cardiac function in 224 women with preeclampsia, including 150 with non-severe disease and 74 with severe preeclampsia.
Researchers assessed several measures of fetal myocardial performance and circulation, including the Tei index, isovolumetric contraction and relaxation times, ejection time, umbilical artery pulsatility, pulmonary artery pulsatility and pulmonary artery peak systolic velocity.
Fetuses in pregnancies affected by severe preeclampsia showed a different cardiovascular profile.
The mean Tei index was higher in severe disease, at 0.55 versus 0.48, while isovolumetric contraction and relaxation times were longer. Umbilical and pulmonary artery pulsatility indices were also higher, while ejection time and pulmonary artery peak systolic velocity were lower.
These associations remained statistically significant after adjustment for gestational age at assessment, maternal age and BMI, and persisted in sensitivity analyses incorporating early-onset preeclampsia and fetal growth restriction.
The clinical outcomes moved in the same direction. Women with severe preeclampsia delivered earlier, their infants had lower birth weights and lower 5-minute Apgar scores, and 23.0% of newborns required NICU admission compared with 5.3% in the non-severe group.
Exploratory analyses found that isovolumetric relaxation time showed the strongest discrimination between severe and non-severe preeclampsia, with an area under the curve of 0.861. The Tei index followed at 0.849.
But performance fell substantially when the researchers tried to predict NICU admission. The best-performing measure, the Tei index, reached an AUC of only 0.650.
The results therefore suggest biological and potentially prognostic relevance, but they do not establish clinical utility.
Why it matters
- HTA bodies: The study illustrates the distance between a promising physiological marker and a clinically useful diagnostic technology. Before additional fetal cardiac measurements are incorporated into formal surveillance pathways, evidence would be needed that they add predictive value beyond existing ultrasound, Doppler and maternal assessments and that using them changes outcomes.
- Payers: More detailed fetal cardiac assessment would require specialist ultrasound capability, clinician time and potentially more frequent monitoring. Any expansion of surveillance would need to demonstrate that additional information reduces emergency delivery, neonatal morbidity or intensive-care use rather than simply generating more testing.
- Industry / innovation partners: Advanced fetal ultrasound, automated measurement and AI-supported image interpretation could make sophisticated cardiac assessment more reproducible. The opportunity is significant, but algorithms should not be built around exploratory thresholds before multicentre validation establishes which measurements actually improve decision-making.
Preeclampsia is a maternal diagnosis, but its consequences are shared across two circulations.
As maternal blood pressure rises and placental function deteriorates, clinicians are watching not only the woman but also the fetus: Is growth slowing? Is blood flow through the placenta becoming more resistant? Is the fetus still tolerating the pregnancy, or is delivery becoming safer than waiting?
A new study suggests there may be another layer of information hidden inside that surveillance.
The fetal heart itself appears to behave differently when preeclampsia becomes severe.
Researchers studying 224 women with preeclampsia measured a series of fetal cardiac and Doppler parameters and compared pregnancies classified as severe with those in which the disease remained non-severe. What emerged was not a single abnormal measurement but a broader pattern of altered cardiac timing and vascular resistance.
One of the clearest differences appeared in the Tei index, also known as the myocardial performance index. Rather than looking only at how forcefully the heart contracts, the measure combines timing information from contraction and relaxation to give a broader picture of cardiac performance.
The average Tei index was 0.55 in fetuses exposed to severe preeclampsia compared with 0.48 in those whose mothers had non-severe disease.
Other measurements moved with it. The periods the fetal heart spent in isovolumetric contraction and relaxation were longer in severe disease, while ejection time was shorter. Resistance-related measures in the umbilical and pulmonary circulation were also higher, while pulmonary artery peak systolic velocity was lower.
Taken together, the findings are consistent with the idea that the fetal cardiovascular system is adapting to a more difficult intrauterine environment.
That possibility is biologically plausible. Preeclampsia is fundamentally connected to abnormal placentation and vascular dysfunction. When placental resistance rises, the fetal circulation does not exist in isolation from it. The heart has to work within that altered haemodynamic environment.
What makes the study more interesting is that the cardiac differences did not disappear when researchers adjusted for factors that could otherwise explain them.
Severe preeclampsia often occurs earlier, and it is frequently accompanied by fetal growth restriction. Both could independently influence cardiac measurements. Yet the associations remained after adjustment for gestational age at the scan, maternal age and BMI, and after additional analyses accounting for early-onset disease and fetal growth restriction.
That strengthens the signal.
It does not make it a clinical test.
The distinction becomes especially important when looking at what happened after birth.
Pregnancies with severe preeclampsia ended earlier and produced smaller babies with lower 5-minute Apgar scores. Nearly one quarter of infants in the severe group were admitted to neonatal intensive care, compared with just over 5% in the non-severe group.
The researchers therefore examined whether the fetal cardiac measurements could help distinguish severe disease or identify babies who would later require intensive care.
Some performed impressively at the first task.
Isovolumetric relaxation time achieved an area under the receiver operating characteristic curve of 0.861 for distinguishing severe from non-severe preeclampsia within the study cohort, while the Tei index reached 0.849.
Those numbers can sound close to diagnostic readiness.
They are not.
The analyses were exploratory and performed in the same population in which the associations were identified. There was no independent validation cohort. Thresholds that perform well in one centre can deteriorate significantly when applied to a different hospital, patient population, ultrasound machine or operator.
More importantly, distinguishing a severe preeclampsia group defined using existing clinical criteria is not necessarily the decision clinicians most need help making.
Preeclampsia severity is already assessed through maternal symptoms, blood pressure, laboratory findings, fetal growth and conventional fetal surveillance. The more valuable question is whether a new cardiac measure predicts something clinicians cannot already predict well.
On that point, the results were much less convincing.
When the researchers examined NICU admission, discrimination was limited. Even the best-performing parameter, the Tei index, achieved an AUC of only 0.650.
That difference tells the real story of the study.
The fetal heart appears to contain information about the physiological severity of preeclampsia. Whether that information is useful enough to change management remains unanswered.
Current fetal surveillance in preeclampsia already has an established architecture. Clinicians assess fetal growth and amniotic fluid, use umbilical artery Doppler to examine placental resistance and employ cardiotocography according to clinical circumstances. Decisions about continued surveillance or delivery are made by combining those findings with maternal status.
The newly studied cardiac parameters are not currently part of that standard pathway.
Adding them would only make sense if they improve it.
That could eventually mean identifying fetal compromise before conventional monitoring becomes abnormal. It could mean differentiating pregnancies that appear similar by maternal criteria but carry different fetal risk. Or it could mean helping clinicians determine which pregnancies require closer surveillance when expectant management is being considered.
But each of those possibilities still needs to be demonstrated.
There is also a practical issue.
Detailed fetal cardiac assessment requires expertise and reproducible measurement. A parameter that works well when obtained by experienced investigators may be considerably less useful if measurements vary between operators or centres.
This is where technology may eventually change the equation.
Automated ultrasound analysis and AI-supported measurement could make timing intervals and cardiac indices easier to obtain consistently. If future multicentre studies confirm that these measures carry independent prognostic value, automation could potentially bring them into wider obstetric practice without turning every preeclampsia assessment into a specialist fetal echocardiography examination.
That future remains speculative.
For now, the study is more important for what it reveals about preeclampsia than for any immediate change to screening.
The maternal blood pressure reading tells only one side of the disease.
Placental Doppler tells another.
The fetal heart may be telling a third.
The challenge for researchers is to prove that listening to that additional signal improves something that matters: the timing of delivery, neonatal morbidity, intensive-care admission or longer-term cardiovascular health.
Until then, these measurements should remain where the evidence places them, as promising markers of fetal adaptation rather than new clinical thresholds.
Severe preeclampsia appears to leave a measurable cardiovascular signature before birth. The next question is whether recognising that signature can actually help clinicians protect the baby.
