OP04.15: Nomograms of fetal intrauterine shunts

Abstract

To generate nomograms for the blood flow velocity waveforms of central fetal intrauterine shunts Foramen Ovale (FO) and Ductus Arteriosus (DA). Data has been extracted from an ongoing, prospective longitudinal observational study of uteroplacental and fetal circulation. After an early dating scan to confirm gestational age, 155 women with singleton pregnancies were scanned serially from 16 weeks onwards at 4 weekly intervals till 24 weeks and two weekly intervals thereafter, till 38 weeks. Congenital anomalies were excluded. Echocardiographic studies of FO and DA flow velocity waveforms were performed. Other serial measurements for the trial included biometric measurements BPD, HC, AC, FL, AFI and Doppler flow velocity waveforms of Umbilical Artery, Middle Cerebral artery, Ductus Venosus and Uterine arteries. Patients with adverse outcomes were excluded and all the women with normal outcomes were included for data analysis. Every two gestational weeks patients were grouped and for these groups, the 5th, 50th and 95th percentiles were calculated for the FO, and DA Peak systolic velocity (PSV) and Pulsatility Index (PI). Gestation—specific reference ranges were constructed for the fetal intrauterine shunts. In normal pregnancies, PI of FO decreased and PI of DA was relatively constant with advancing gestation. However, the PSV of FO and DA increased linearly with gestational age. Reference ranges for fetal central intrauterine shunts have been established which may enhance our understanding of fetal compromise and aid in evaluating management of complications like fetal growth restriction as well as congenital cardiac malformations.