Second-trimester amniotic fluid or maternal serum interleukin-10 levels and small for gestational age neonates

OBJECTIVE: To evaluate if interleukin-10 levels in either early second-trimester amniotic fluid (AF) or maternal serum can be utilized as a predictor of the subsequent occurrence of small for gestational age (SGA) infants after controlling for gestational age at delivery. METHODS: We identified patients who underwent genetic amniocentesis for standard genetic indications or maternal blood sampling for maternal serum alpha-fetoprotein (MSAFP)/triple screen between January 1992 and February 1995 with available follow-up delivery data. Small for gestational age was defined as birth weight less than the tenth percentile for gestational age. Control patients were matched for gestational age at delivery, maternal age, race, and parity with at least two controls for each study patient. We excluded patients with maternal immune disease, chronic hypertension, diabetes, asthma, congenital heart disease, multiple gestation, and fetuses with structural or chromosomal anomalies. Second-trimester AF and serum samples were assayed for interleukin-10. Potential confounding variables considered were MSAFP level, smoking history, pregnancy-induced hypertension, and neonatal gender. The interleukin-10 levels were normalized using natural log transformation for statistical analysis. Statistical analysis included chi 2, Fisher exact test, and analysis of variance, with P < .05 considered significant. RESULTS. From the AF data base, 18 patients (6%) delivered SGA neonates and were matched with 46 controls. From the maternal serum data base, 13 patients (7%) delivered SGA neonates and were matched with 45 controls. Neither AF nor maternal serum interleukin-10 levels were significantly different in patients subsequently delivering SGA neonates compared with controls (AF: median 21.0 pg/mL. [range 13.8-27.6] versus 17.5 pg/mL. [range 8.9-362.12], P = .18; serum: median 15.7 pg/mL [range 9.9-73.5] versus 18.7 pg/mL [range 9.7-71.7], P = .60, respectively). No significant differences were identified in gestational age at sampling, maternal smoking history, pregnancy-induced hypertension, or elevated MSAFP in patients delivering SGA neonates compared with controls (P > .05 for each). As expected, birth weight was significantly lower in patients delivering SGA neonates compared with controls (P < .001). CONCLUSION: Second-trimester AF or maternal serum interleukin-10 levels are not predictive of subsequent delivery of SGA infants.