Blood rheology at term in normal pregnancy and in patients with adverse outcome events
Authors: von Tempelhoff Georg-Friedrich , Velten Eva , Yilmaz Asli , Hommel Gerhard , Heilmann Lothar , Koscielny Jürgen 
Published: December 2019

Plasma volume expansion of more than 1.5 l and sustainable activation of the hemostatic system that results in a steady rise of the fibrinogen/fibrin turnover are contemporary physiological events during normal pregnancy. In contrast, adverse outcome of pregnancy i.e. pre-eclampsia commonly coincide with hemo concentration and over activation of blood coagulation both of which alter blood rheology.

On the basis of 4,985 consecutively recorded singleton pregnancies values range of blood rheological parameters in women with normal and complicated outcome of pregnancy at the time of their delivery were compared.

Plasma viscosity (pv) was determined using KSPV 1 Fresenius and RBC aggregation (stasis: E0 and low shear: E1) using MA1-Aggregometer; Myrenne.

Seventy-nine point four percent (n=3,959) had normal pregnancy outcome and 1,026 with adverse outcome of pregnancy had pre-eclampsia (8.4%; n=423), had newborn with a birth-weight < 2,500 g (9.5%; n=473), had early-birth before week 37 (9.3%; n=464), and/or were diagnosed with intra uterine growth retardation (IUGR) (5.0%; n=250). In women with normal pregnancy outcome mean (±SD) of pv was 1.31±0.09 mPa s, of E0 was 21.6±5.3, and of E1 was 38.4±7.9 while in women with adverse outcome means for rheological parameters were statistically significantly different i.e. pv: 1.32±0.08 mPa s; p=0.006, E0: 22.1±5.5; p=0.002 and E1: 39.5±8.5; p=0.0006. Subgroup analysis revealed statistical significant lower pv in women who either had pre term delivery or a low birth-weight child (p<0.005) as compared to women who had normal pregnancy outcome while patients with pre-eclampsia had markedly higher low shear and stasis RBC aggregation (p<0.0001). None of the rheological results at term were correlated with either maternal age (r<0.04), BMI (r<0.09), maternal weight gain until delivery (r<0.04), or fetal outcome such as APGAR-score (r<0.09) art. pH in the umbilical cord (−0.05<r<0.04), fetal birth-weight (r<0.04). Women who did vs. did not receive iron supplementation during pregnancy had lower pv (p<0.0001) and higher E0 (p<0.01) while smokers vs. non-smokers had lower E0 (p=0.0002).There was a strong correlation between hemoglobin concentrations and pv at term (spearman r=0.15; p<0.0001).

To our knowledge this is the largest trial that consecutively assessed blood rheological parameters in pregnant women at term. Distribution of pv and RBC aggregation was studied in women with normal and complicated pregnancy. We found lower pv and increased RBC aggregation in patients with different adverse outcome of pregnancy compared to normal pregnancy. Interestingly, in pre-eclampsia hemo concentration and increased fibrinogen turnover due to enhanced coagulation activation are weighty co factors of pv but were associated with lower pv in patients with pre-eclampsia. However, coincidental increased RBC aggregation and hemo concentration may potentially derogate blood flow in the materno-fetal unit that is commonly traceable using vessel duplex ultra sound in pre-eclampsia.