The most common maternal risk factor associated with neonatal complications during delivery is obesity. Although gestational diabetes mellitus (GDM) occurs in 5–10% of the pregnant population, obesity, by virtue of its prevalence, far outpaces GDM as the most important underlying risk factor for increased fetal adiposity. The mechanisms underlying maternal insulin resistance may play an important role in the diversion of excess fuels to the fetus. Maternal adipose depots increase in early pregnancy, followed by increased adipose tissue lipolysis and subsequent hyperlipidaemia, which mainly corresponds to increased triglyceride levels (TG). A positive correlation between maternal TG and infant body weight or fat mass has been found in both GDM and non-GDM obese women. Increased oxidative stress, altered adipokines, and inflammatory cytokines have also been found in obese pregnant women, suggesting an adverse metabolic outcome even in normoglycemic conditions.