Heart rate variability after a high-risk birth: differences depend on age and context

What the researchers compared

Heart rate variability, or HRV, is used to assess autonomic nervous system function. The authors examined differences between people with a perinatal risk factor and healthy controls born at term, only after hospital discharge.

The literature search, conducted through April 2025, included 27 studies and yielded 156 effect sizes. The populations studied ranged from early childhood to adulthood. The factors examined included preterm birth, low birth weight and fetal growth disorders.

An overall result that masks different situations

The overall effect was modest and not statistically significant: d = −0.21, with p = 0.14. This standardized effect size does not represent a 21% reduction in HRV. Heterogeneity was high, with an I² of 89.3%, which limits the relevance of a pooled average across all these populations.

The most consistent reductions in HRV were found in people born small for gestational age or who had experienced intrauterine growth restriction. For preterm birth and low birth weight, no significant overall effect was found, but results varied substantially across studies and age groups.

Younger samples showed more pronounced differences than older samples. This suggests an age-dependent association, without demonstrating progressive normalization within the same person.

What this review changes—and what it does not

These findings suggest that the causes of perinatal risk should be distinguished rather than grouping all high-risk births together. They do not establish that preterm birth alone leads to a lasting reduction in HRV.

Most studies were cross-sectional: they compared groups at a single point in time rather than following the same people over time. Differences between age groups therefore cannot distinguish possible catch-up from survivor bias.

Finally, this review concerns an indicator of autonomic function. It demonstrates neither that a difference in HRV predicts a clinical complication nor that an intervention intended to modify it would improve health.

What we can take away

The strongest conclusion is a distinction: associations with HRV vary according to the perinatal risk factor and age. An average value does not capture every trajectory.