Problem: To evaluate the independent ability of midtrimester amniotic fluid tumor necrosis factor-alpha (TNF-alpha) in the prediction of small-for-gestational-age (SGA) infants.
Method of study: In this case-control study, patients delivering a SGA infant were matched with controls based on GA at delivery, maternal age, race, and parity. Patients with immune disease, chronic hypertension, diabetes, asthma, congenital hearts disease, multiple gestation, and fetal anomalies were excluded. Amniotic fluid samples were immunoassayed for TNF-alpha. Potential confounding variables evaluated were maternal serum alpha-fetoprotein level, smoking history, pregnancy induced hypertension, and neonatal gender. Statistical analysis included Fisher's exact test and ANOVA after log transformation with P < 0.05 considered significant.
Results: Eighteen patients delivered SGA neonates and were matched with 41 controls. No significant differences were identified in the confounding variables between patients with SGA neonates and controls. Amniotic fluid TNF-alpha levels were not significantly different between patients subsequently delivering SGA neonates and controls [median 7.63 (range 0.25-16.1) pg/mL versus 9.39 (0.25-66.9) pg/mL, P = 0.8].
Conclusions: Midtrimester amniotic fluid TNF-alpha levels are not predictive of SGA neonates when compared with controls matched for gestational age at delivery.