Clinical chemistry alterations in pregnancy and oral contraceptive use.

In this study the effects of pregnancy and oral contraceptive use on plasma glucose concentrations, hepatic, renal, and thyroid function tests, and their relationships to plasma lipoprotein lipids after an overnight fast are compared. Observations were made in 546 pregnant women at 36 weeks' gestation, 56 women using oral contraceptive hormones, and 77 women not using sex hormones. All subjects were randomly selected from defined populations. Compared with nonpregnant women not using hormones, median plasma glucose concentrations are 3% lower with oral contraceptive use and 17% lower in pregnancy. Plasma total bilirubin concentrations are lowered by similar amounts in oral contraceptive users (29%) and in pregnancy (32%). Serum glutamic oxaloacetic transaminase is slightly lower among hormone users (9%) but is significantly higher (27%) in pregnancy. Alkaline phosphatase is significantly lower in oral contraceptive users (23%) but is higher in pregnancy (86%). Serum globulin concentrations are unaffected by pregnancy or oral contraceptive use. Compared with nonusers, thyroxine is 30% higher in oral contraceptive users and 100% higher during pregnancy. Serum creatinine is unaffected by sex steroid use but is 28% lower in pregnancy. Associations of these test results with plasma hormone concentrations corroborate hormonal mechanisms and suggest that some alkaline phosphatase and serum glutamic oxaloacetic transaminase come from the placenta. Relationships of these clinical measurements to lipoprotein lipids in pregnancy are generally weak and do not point to important controlling relationships, but effects similar to those seen in nonpregnant subjects are seen with hyperglycemia (associated with elevated triglyceride) and elevated thyroxine levels (associated with lower cholesterol and triglyceride).(ABSTRACT TRUNCATED AT 250 WORDS)