Reference intervals for 23 common biochemical parameters during pregnancy and the first six postpartum months

The concentration of many biochemical parameters changes significantly during pregnancy and the postpartum period, causing a need for specific reference values for biochemical parameters in these life periods. We have collected blood samples in pregnancy week 18, 28 and 36 and six weeks, four months and six months postpartum from 139 healthy women. Blood samples from 59 healthy never-pregnant women were included as controls. Serum samples were analyzed for 23 common biochemical parameters and reference intervals for pregnancy and postpartum periods were computed with the non-parametric method in accordance with recommendations from IFCC and CLSI. The dynamics of different biochemical parameters during and after pregnancy vary considerably between parameters. Some analytes like serum amylase and HDL cholesterol do not differ from never-pregnant values. Of the 23 parameters, serum alkaline phosphatase, chloride, gamma-glutamyl transferase and sodium and urea which were still significantly changed at six months postpartum compared to never-pregnant women. The physiological changes related to pregnancy and lactation have profound effects on biochemical parameters, denoting the use of specific reference intervals for both pregnancy and the postpartum period.