P05.10: Perinatal outcome of small for gestational age babies born after 34 weeks of gestation: role of prenatal surveillance

Objective: Cardiac disproportion often signifies important disease resulting in a postnatal duct-dependent circulation. Diagnostic accuracy was prospectively assessed in fetuses referredwith disproportion detected during routine obstetric screening (1997–2002). Methods: We trained sonographers to recognise cardiac disproportion in four transverse views. Fetuses without disproportion; isolated septal defects, balanced atrioventricular septal defects, tetralogy of Fallot or double outlet right ventricle with large pulmonary arteries, simple transposition or moderate valvar stenosis were excluded. Results: 293/1721 cardiac referrals were for suspected cardiac sonographic anomalies, 109 had disproportion confirmed (60% left sided hypoplasia). Diagnosis included isomerism (6), persistent left superior caval vein (LSVC) (6), chromosomal defects (15), and extracardiac malformations (25). Duct-dependent postnatal circulation was likely in 83%. 12.8% with disproportion had no important cardiac abnormality – 5 had aneuploidy, hydrops or vein of Galen aneurysm, 7 were managed as suspected coarctation (CoA) (3 mild arch hypoplasia (1 45XO), 4 normal). Continuous flow on colour and Doppler at the isthmus (5) aided CoA diagnosis, but one with restrictive foramen excluded it. LSVC occurred in 5.5% disproportion vs. 0.5% referred population (p = 0.00001). Disproportion was not confirmed in 1.5% referrals. Neonatal outcomes were confirmed in all but one that moved abroad. Conclusions: Recognition of cardiac disproportion is a simple but effective protocol with a low false positive referral rate (33/1721, 1.9%) in second trimester screening.