New reference values for routine blood samples and human neutrophilic lipocalin during third-trimester pregnancy

Reference values are usually based on blood samples from healthy men or non-pregnant women. Blood samples from pregnant women may be compared with these reference values. Correct references for pregnancy can be extremely important for clinical decisions such as ablatio placentae, appendicitis, premature rupture of membranes and preeclampsia. Previous studies of normal variations during third-trimester pregnancy are incomplete. Blood samples during pregnancy weeks 33, 36 and 39 as well as 1-3 h postpartum were collected from pregnant women with dietary iron supplement and at least one previous pregancy without a history of hypertension or preeclampsia. When the sampled values were compared with the present reference values from men and non-pregnant women, the following differences were found during normal pregnancy: Haemoglobin and ferritin were reduced, CRP was slightly elevated, WBC (white blood cell count) and HNL (human neutrophilic lipocalin) were elevated during pregnancy and significantly increased postpartum. Albumin was reduced. ALT and AST were slightly elevated and GGT was unchanged during pregnancy. ALP, D-dimer and fibrinogen were elevated. Uric acid increased during the third trimester and thrombocyte count decreased. Separate reference values for pregnant women are essential for correct diagnostic decisions during third-trimester pregnancy. Elevated levels of D-dimer do not necessarily indicate ablatio placentae. A diagnosis of progressive preeclampsia cannot be based on increasing uric acid levels and reduced platelet count in a stable clinical condition. HNL signals activation of neutrophilic granulocytes and can thereby offer a helpful tool for diagnosing infection during pregnancy and postpartum.