The role of the sympathikus system in fetal programming

Objective: Intrauterine under nutrition during fetal development is associated with an increased risk for cardiovascular and metabolic diseases in later life. Mechanisms responsible for these changes are thought to be the result of an unfavourable intrauterine programming of systems. We hypothesized that increased sympathic activity of the fetus persists postnatally and therefore may account for unfavourable adaptions of the cardiovascular system. Therefore we analyzed the sympathicus/vagus-system in growth retarded fetuses pre- and postnatally.

Methods: CTGs of small for gestational age (SGA) babys (<5. perc.) and normal controls (AGA) were analyzed for FHR and FHR variability. 24h Holter ECGs 3 days post partum were analyzed for various heart rate variability parameters indicating sympathic system activiy.

Results: 20 SGA fetuses were compared to 20 AGA fetuses. Prenatal CTG analysis revealed a mean heart rate of 140 bpm in both SGA and AGA fetuses. Fetal heart rate variability was 14.6 in SGA and 16.8 beats in AGA fetuses revealing no significant difference. Postnatal geometric- and time-domain indexes of HRV assessed by 24-hour Holter monitoring revealed no significant alterations in SGA compared to AGA fetuses

Conclusion: Heart rate variability as marker for sympathic activation is not altered in SGA newborns. Therefore, fetal adaption to placental insufficiency does not result in imbalance of the sympathicus/vagus system postnatally.