Impact on fetal mortality and cardiovascular Doppler of selective ligature of uteroplacental vessels compared with undernutrition in a rabbit model of intrauterine growth restriction.

OBJECTIVES

To compare the impact on birth weight, mortality and fetal haemodynamic changes of selective ligature of uteroplacental vessels vs maternal undernutrition as experimental models of intrauterine growth restriction in the pregnant rabbit.

METHODS

Three groups of NewZealand rabbit fetuses were compared: controls (n = 60), selective ligature of 40-50% of uteroplacental vessels (n = 38) and 70% diet restriction (n = 19), both starting at 25 days of gestation. Cardiovascular Doppler evaluation was performed before delivery in a subgroup of fetuses (15 controls and cases from surgical model and 10 fetuses from the undernutirtion model) before delivery including: umbilical artery pulsatility index (UAPI), middle cerebral artery pulsatility index (MCAPI), ductus venosus pulsatility index (DVPI), aortic isthmus pulsatility index (AoIPI), isovolumetric contraction time, ejection time, isovolumetric relaxation time (IRT), and myocardial performance index. Fetuses were delivered at 30 days of gestation by caesarean section and biometric measurements were recorded.

RESULTS

The mortality rate was significantly higher in the surgical group (54.2%) than in the undernutrition (5%) and control (14.3%) groups (p < 0.001). Changes of biometrical measurements increased across experimental groups, being more pronounced in the surgical model. Ultrasound evaluation demonstrated linear trend for increased values in DVPI (p = 0.003) and AoIPI (p = 0.029), and IRT (p = 0.003) across study groups, but statistically significant changes were only observed in the surgical model. No significant differences were observed in the UAPI or MCAPI.

CONCLUSIONS

While animal models fail to perfectly reproduce the human condition, selective ligature of uteroplacental vessels reproduces more closely cardiovascular features observed in human fetuses with intrauterine growth restriction when compared with undernutrition.