Reference values for biochemical tests during pregnancy: analysis of the PRECAREbio Cohort and correlation with precarious status.

Objective: To establish normal current values of various biochemical parameters during pregnancy in the northern area of Paris (France) in a subgroup from the PreCARE cohort and to study their changes according to the term of pregnancy, and to determine the influence of maternal precarity.

Design: The PreCAREbio cohort of pregnant women was defined in the PreCARE study, a multicenter cohort study.

Setting: Participants completed detailed questionnaires at enrolment and immediately postpartum. Data were collected prospectively. 26 biochemical parameters were longitudinally assessed.

Population: All women registered to deliver or who delivered at one of the four participating university hospitals in Paris between October 2010 and November 2011 were eligible for study inclusion (n=10,419).

Methods: We studied 26 biochemical markers during pregnancy and the influence of maternal social deprivation.

Main Outcome Measures: Baseline values for 26 biochemical markers and their changes according to the term of pregnancy, and the influence of maternal social deprivation on these biochemical markers.

Results: 386 patients with 1733 blood samples recruited in one of the four centers in the PreCARE cohort were included. Baseline concentrations (median, 2.5th and 97.5th percentile) for each marker and did not differ at the different time points. Mean concentrations of each biochemical marker did not differ between socially deprived women and non-socially deprived women.

Conclusions: We have established normal values for 26 biochemical parameters during pregnancy. We have also shown no difference in these values between socially deprived and non- socially deprived women.