The relationship between maternal c-type natriuretic peptide levels and fetal growth restriction.

OBJECTIVE: To investigate maternal serum C-type natriuretic peptide (CNP) levels in pregnancies with different fetal growth patterns and to evaluate the ability of CNP to discriminate pathological fetal growth restriction (FGR) from non-pathological fetal smallness. METHODS: This prospective study included 180 singleton pregnancies classified as appropriate-for-gestational-age, constitutionally small with normal Doppler, or pathological FGR with abnormal Doppler. Maternal serum) levels were measured, and appropriate statistical methods were applied to evaluate their ability to distinguish pathological FGR from non-pathological smallness. RESULTS: Maternal age, gravidity, and parity were similar across groups (p > 0.05), while BMI differed significantly (p < 0.001). Gestational age at delivery and birth weight decreased progressively from Group 1 to Group 3 (p < 0.001). Maternal serum CNP levels varied significantly (p < 0.001), being highest in pathological FGR. Post-hoc analysis confirmed higher CNP in Group 3 versus Groups 1 and 2 (p < 0.001), with a smaller difference between Groups 1 and 2 (p = 0.039). CNP correlated negatively with gestational age (r = - 0.277) and birth weight (r = - 0.466) (p < 0.001). ROC analysis showed excellent accuracy for detecting pathological FGR (AUC = 0.908, 95% CI: 0.857-0.959), with a cutoff of 644.3 pg/mL yielding 95% sensitivity and 80.8% specificity. CONCLUSION: Maternal serum CNP levels are significantly elevated in pregnancies with pathological fetal growth restriction but not in constitutionally small fetuses. This suggests that CNP reflects placental insufficiency rather than normal smallness and may serve as a useful biomarker to differentiate pathological from non-pathological fetal growth.