Gender differences in amniotic fluid cytokine levels

Objective: Placental trophoblast invasion and amniotic fluid cytokine receptor levels have been reported to vary with fetal gender. We investigated whether fetal gender affects amniotic fluid levels of the inflammatory cytokines interleukin (IL)-6 and IL-10 and the pro-angiogenesis cytokine angiogenin. Methods: Specimens from singleton gestations undergoing mid-trimester amniocentesis for genetic indications were used. Inclusion criteria were (1) outcome information available, (2) no structural or chromosomal anomaly and (3) no conditions associated with preterm delivery. Amniotic fluid IL-6, IL-10 and angiogenin levels were measured by immunoassay. Statistical analysis included the Mann-Whitney U test and Fisher's exact test with p < 0.05 indicating significance. Results: A total of 74 samples were analyzed. Angiogenin levels were significantly lower in amniotic fluid samples from pregnancies with a male than with a female fetus (median (range): 22.2 (5.9-66.4) vs. 32.0 (11.4-159.2) ng/ml, p = 0.007), in contrast to no differences in amniotic fluid IL-6 and IL-10 levels (p = 0.4 and p = 0.1, respectively). In pregnancies with male fetuses delivering preterm (< 37 weeks), angiogenin was also detected at lower levels (p = 0.02). There were no gender differences with respect to race, nulliparity or maternal age. Conclusion: Angiogenin levels, but not IL-6 or IL-10 levels, are significantly lower in second-trimester amniotic fluid of women with male compared with female fetuses, including those women delivering preterm.