Placental structure and inflammation in pregnancies associated with obesity

Background: Pre-gravid obesity is associated with increased morbidity and mortality for both mother and offspring. Recent studies have demonstrated a heightened inflammatory response both systemically and locally within the adipose and placental tissue in women with pre-gravid obesity, which may play a role in mediating the adverse pregnancy outcomes. The aim of this study was to characterise the maternal and placental inflammatory status and investigate associated changes in placental structure in obese women.

Methods: The pro-inflammatory status of a cohort of 47 non-obese (BMI 20-25 kg/m(2)) and 33 obese (≥30 kg/m(2)) women was characterised by measuring maternal circulating levels and placental gene expression of pro-inflammatory cytokines, and quantifying immune cell populations within the placenta. The effect of pre-gravid obesity on placental structure was investigated by examining placental maturity, vessel density, the formation of syncytial knots and sprouts, and the degree of fibrin deposition, chorangiosis and muscularisation of vessel walls.

Results: Maternal obesity was associated with significantly greater IL-1β (p < 0.05), IL-8 (p < 0.05), MCP-1 (p < 0.001) and CXCR2 (p < 0.05) mRNA expression within the placenta and higher circulating maternal levels of IL-6 (3.30 ± 0.38 vs. 1.77 ± 0.15 pg/ml) (p < 0.001) compared with non-obese women. There were no differences in the number of CD14(+), CD68(+) cells or neutrophils within the placental villi of non-obese and obese women. However there were significantly higher numbers of neutrophils within the interstitial space (p < 0.05). Greater muscularity of placental vessel walls was associated with maternal obesity (p = 0.03), however no other associated structural changes were observed.

Conclusions: Our findings show that although pre-gravid obesity was associated with greater expression of placental pro-inflammatory cytokines and higher circulating IL-6 in pregnancy, there were no major differences in immune cell populations within the placental villi and only a greater degree of muscularity in the vessel walls.