Fetal Tibial Artery Doppler in Late IUGR Fetuses: A Longitudinal Study

Introduction: Late-onset intrauterine fetal growth restriction (IUGR) is a common pregnancy complication diagnosed in 5–10% of pregnant women worldwide. Under the impact of hypoxia, the fetus develops a protective mechanism of adaptive changes occurring in the cerebral circulation (“brain-sparing effect”). Materials and methods: We conducted detailed longitudinal Doppler examinations and the monitoring of the fetal condition in 53 IUGR fetuses. Doppler measurements of the pulsatility index in the fetal tibial (TA-PI), umbilical (UA-PI), and middle cerebral arteries (MCA-PI) were performed, and the cerebral placental ratio (CPR) was determined on a weekly basis from the 33rd week to the birth. Results: The longitudinal analysis showed a significant increase in the TA-PI. The UA showed a plateau, but no increase was detected near term. The MCA-PI and CPR showed a progressive decrease in values from inclusion to delivery. Our findings indicate that the increase in the TA-PI was the first sign of the aggravating state of the fetus with the changes registered from the 35th week. The parameters of the UA-PI did not show significant changes, while the MCA and CPR became abnormal later from the 37th week. Conclusions: These observations can serve towards the development of guidelines for detecting the deteriorating signs and intervention timing in IUGR during late pregnancies.