Serum paraoxonase (EC 3.1.1.2) may be implicated in the lipid metabolism. In order to substantiate this view we conducted a longitudinal study of interrelationships of serum paraoxonase, lipids and apolipoproteins during pregnancy. Fasting serum levels of paraoxonase, serum lipids (total, HDL and LDL cholesterols, triglycerides) and apolipoproteins (AI, All and B) were estimated in 91 pregnant women at 28 and 32 weeks of gestation and 6 weeks after delivery, and 40 nonpregnant women. Serum paraoxonase, total HDL and LDL cholesterol levels were significantly higher during pregnancy along with corresponding apolipoprotein (p < 0.001). The most striking increase was seen in serum triglycerides and paraoxonase levels (p < 0.001). Serum paraoxonase levels had a significant correlation with triglycerides (r: 0.45–0.60) and ApoAH (r: 0.32–0.41) in both pregnant and nonpregnant states (p < 0.001). Moreover, both serum paraoxonase and triglyceride levels at 28 weeks of pregnancy were negatively correlated with birth weight (r: 0.3, p < 0.05), suggesting a possible role of paraoxonase in energy delivery for fetal development derived from maternal hypertriglyceridemia.