Maternal and fetal cardiovascular response to moderate-to-vigorous intensity exercise in singleton and twin pregnancies

OBJECTIVE: Current guidelines suggest limiting physical activity in pregnant individuals carrying twins but this recommendation is not based on empirical evidence. We assessed maternal and fetal cardiovascular response to submaximal exercise testing in singleton versus twin pregnancies. METHODS: Females with a singleton (n=12, 26±5 weeks of gestation, 33±3 years of age) and twin (n=12, 26±5 weeks of gestation, 33±2 years of age) pregnancies were recruited. Maternal cardiac function (heart rate (HR); cardiac output (CO), stroke volume (SV) and ejection fraction (EF) via echocardiography) and mean arterial pressure (MAP; photoplethysmography) were measured at rest and during incremental cycling exercise to 70% HR reserve. Fetal HR and umbilical blood flow were measured pre-exercise and post-exercise. RESULTS: Compared to those with singleton pregnancies, women pregnant with twins had a higher resting HR (95±12 vs 83±6 bpm; p=0.003) and MAP (91±8 vs 82±9 mm Hg; p=0.013), but similar to SV, EF and CO. In response to a submaximal cycling exercise test, individuals with twins and singletons had similar changes in HR (Δ46±22 vs Δ56±11 bpm; p=0.16), CO (Δ6.2±3.9 vs Δ7.2±2.8 L/min; p=0.50), and ΔMAP (Δ14±7 vs Δ15±6 mm Hg; p=0.75). Fetal HR was unchanged in response to exercise at 70% HR reserve in both groups (singleton: Δ-1±4 vs twin: Δ0±4; p=0.53), with no incidence of fetal bradycardia or tachycardia. Umbilical blood flow was unchanged. CONCLUSION: While resting haemodynamics were generally higher in individuals with twin compared with singleton pregnancies, the cardiovascular response to exercise was not different between groups and exercise did not impact fetal well-being.