Respiratory morbidity among offspring misclassified as growth restricted.

Objective: An ultrasound-based diagnosis implies that some fetuses suspected to be growth-restricted (FGR) are discovered at birth to be appropriately grown (appropriate for gestational age [AGA] birth weight, between the 10th and 90th percentile). These fetuses may thus be exposed to unnecessary medical interventions, including early labor induction. In this study, we have evaluated the long-term respiratory health of offspring misclassified as FGR.

Study Design: A population-based cohort analysis was conducted, including deliveries of AGA singletons between 1991 and 2021 at a tertiary referral hospital. Incidence of morbidity due to various respiratory conditions was compared between AGA offspring with prenatal diagnosis of FGR, and those without a false diagnosis of FGR. The Kaplan-Meier approach was used to estimate cumulative morbidity incidence. The stratified Cox proportional-hazards model was used to control for confounders.

Results: A total of 324,620 deliveries of AGA newborns were included in the analyses; 3249 of them (1.0%) were misclassified prenatally as FGR. The FGR subgroup delivered at an earlier gestational age (36.7 vs. 39.1 weeks, p < .001) and had more than 25% higher incidence of respiratory-related morbidity during childhood (33.2% vs. 26.5%), specifically related to asthma and obstructive sleep apnea (p < .001 for all). A higher cumulative morbidity rate due to respiratory conditions was observed in the Kaplan-Meier survival curve (log-rank p value < .001). This association between FGR and respiratory morbidity was independent of preterm delivery, maternal age, cesarean delivery, and child's birth year (adjusted hazard ratio = 1.14, 95% confidence interval: 1.07-1.21, p < .001), using a Cox proportional hazards model.

Conclusion: AGA newborns misclassified as FGR, are at an increased risk for long-term respiratory morbidity during childhood and adolescence.