Early postnatal transitional circulation in fetal growth restricted neonates

Background: Fetal growth restriction (FGR) may impact early postnatal transitional circulation.

Aim: Echocardiographic assessment of left ventricular cardiac output, superior vena cava (SVC) and ductus venosus (DV) blood flow in FGR neonates first three days after birth.

Study design: Prospective observational study.

Subjects: FGR and Non-FGR neonates.

Outcome measures: Left ventricular cardiac output, SVC and DV blood flow day one, two, and three.

Results: Adjusting for gestational age (GA), birth weight, sex, and twin/singleton, flow measurements were similar between Late-FGR (GA ≥ 32 weeks, n = 23) and Non-FGR (GA ≥ 32 weeks, n = 39). On day three, Late-FGR had significantly lower left ventricular stroke volume (Estimated Marginal Means (Standard Error) 0.99 (0.08) vs 1.22 (0.06) mL/kg, p = 0.027) and higher heart rate (134 (5) vs 119 (4) beats/min, p = 0.032). Left ventricular cardiac output and left ventricular stroke volume decreased significantly from day one to three in both groups; Late-FGR 170 (8) to 149 (8) mL/min/kg, p = 0.007, and 1.34 (0.07) to 1.17 (0.07) mL/kg, p = 0.015, and Non-FGR 161 (6) to 144 (6) mL/min/kg, p = 0.002, and 1.27 (0.06) to 1.16 (0.06) mL/kg, p = 0.021. SVC flow remained unchanged from day one to three in Late-FGR (92 (6) to 83 (6) mL/min/kg, p = 0.161) and decreased significantly in Non-FGR (83 (5) to 71 (5) mL/min/kg, p = 0.021). DV blood flow remained unchanged. No measurements differed between Early-FGR (GA 30⁺⁰-31⁺⁶ weeks) and Late-FGR.

Conclusions: Late-FGR had limited impact on left ventricular cardiac output, SVC and DV blood flow in early neonatal period. Most adaptive circulatory changes occurred early during transition.