Oxidative stability of low density lipoproteins and vitamin E levels increase in maternal blood during normal pregnancy

In 24 healthy pregnant women, parameters related to the oxidative stability of low density lipoproteins (LDL) were determined at three times during pr egnancy and shortly after delivery. The fatty acid composition of plasma ph ospholipids (PL) and the plasma concentrations of vitamin E, vitamin A, and p-carotene were assessed in the same samples. Total triglyceride (TC), tot al cholesterol, LDL-cholesterol, and high density lipoprotein (HDL)-cholest erol concentrations were also determined. The length of the lag phase of is olated LDL challenged with CU2+ ions significantly increased with the progr ession of pregnancy. The oxidation rate and the amount of conjugated dienes formed increased and reached a maximum at 29-37 wk of pregnancy. Total TG, cholesterol, and LDL-cholesterol reached a maximum in the third trimester of pregnancy. beta -carotene remained stable, vitamin A decreased, and vita min E significantly increased throughout pregnancy. Vitamin E plasma concen tration correlated positively with the length of the lag phase. The increas ed levels of vitamin E could contribute to the higher resistance of LDL tow ard oxidation with progressing gestation, measured by the prolonged lag pha se. Further more, vitamin E plasma levels correlated positively with TG con centration but not with LDL-cholesterol. The level of polyunsaturated fatty acids in PL decreased with the progression of pregnancy. No correlation wa s found between the fatty acid composition of plasma FL, nor with the chole sterol concentration, and the parameters studied related to the oxidative s tability of LDL. The major finding of this study is the increased oxidative resistance of LDL with progressing gestation.