Acute effect of high-intensity interval training on fetal blood flow distribution

  1. HMS Skarstad
  2. S Skrede
  3. KL Haganes
  4. ER Ashby
  5. MAJ Sujan
  6. K Deibele
  7. H Mørch
  8. G Haugen
  9. KÅ Salvesen
  10. T Moholdt
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Abstract

Objectives

To examine the acute effects of a single bout of high-intensity interval training (HIIT) on fetal blood flow distribution during the third trimester of pregnancy.

Methods

Thirty-four healthy pregnant participants (mean age 31.6 years, standard deviation (SD) 4.1; gestational week 33.8 (SD 0.4) completed eight 30-second high-intensity cycling work-bouts interspersed with 2-minute rest periods. Fetal heart rate (FHR), maternal blood pressure, and Doppler-derived blood flow indices in the middle cerebral artery, umbilical artery and vein, and ductus venosus were assessed before and after exercise. We estimated fetal liver blood flow and the ratio of umbilical vein flow to ductus venosus. Maternal heart rate (HR) and FHR were recorded throughout exercise. Paired t -tests compared pre- and post-exercise values.

Results

No significant changes were observed in fetal blood flow indices or distribution following exercise. Average maternal HR and FHR during the work-bouts were 158 bpm (SD 16) and 152 bpm (SD 12), respectively. Following HIIT, maternal systolic blood pressure increased by 5 mmHg (95% CI 1 to 8, p =.014), maternal HR by 22 bpm (95% CI 15 to 28, p <.001), and FHR by 13 bpm (95% CI 10 to 17, p <.001). We recorded 16 instances of FHR above normal range during HIIT.

Conclusion

A single HIIT session in late pregnancy increased maternal blood pressure and HR and transiently elevated FHR but did not affect fetal blood flow indices or distribution. Brief episodes of fetal tachycardia were observed but appeared to be clinically insignificant. Future research should investigate the effects of repeated HIIT exposure during pregnancy.

What is already known on this topic

  • Moderate-intensity exercise during pregnancy is considered safe and beneficial for maternal and fetal health.

  • High-intensity exercise during pregnancy may transiently affect fetal heart rhythm, including brief episodes of fetal tachycardia or arrhythmia.

What this study adds

  • This study provides a comprehensive assessment of the acute effects of a single high-intensity interval training (HIIT) session on fetal blood flow indices and blood flow distribution, including fetal liver perfusion, during pregnancy.

  • A single HIIT session did not alter fetal blood flow measurements despite transient increases in fetal heart rate.

How this study might affect research, practice or policy

  • Evidence regarding the safety of HIIT during pregnancy remains limited.

These findings suggest that acute HIIT does not adversely affect fetal blood flow parameters in healthy pregnancies and may support inclusion of HIIT as a time-efficient exercise option during pregnancy

Article activity feed

  1. Version published to 10.64898/2026.05.27.26354197 on medRxiv