Changes in protein C and protein S levels in normal pregnancy.
OBJECTIVE
The objective of the study was to determine the normal changes in the plasma concentrations of protein C and protein S that occur during each trimester of pregnancy.


METHODS
The study was a prospective cross-sectional study of 91 normal pregnant women who had plasma concentrations of protein C and protein S measured during the first, second, and third trimesters.


RESULTS
There was no statistically significant change in antigenic or functional protein C levels during normal pregnancy. Total protein S levels also remained unchanged. Free protein S levels fell significantly from first to second trimesters (0.45 U/ml mean to 0.26 U/ml mean, p < 0.001), but no further fall occurred during the third trimester.


CONCLUSIONS
The second-trimester fall in free protein S levels is a physiologic pregnancy adaptation. Women with a thromboembolic event appearing for the first time during pregnancy should have investigations for protein S deficiency delayed until the postpartum period, to avoid misdiagnosis and treatment.
Department of Obstetrics and Gynecology, University of Ottawa, Ontario, Canada.
W
W
Faught
P
P
Garner
G
G
Jones
B
B
Ivey
D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D009994:Osmolar Concentration; D011247:Pregnancy / Q000097:blood*; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D011446:Prospective Studies; D011486:Protein C / Q000378:metabolism*; D017293:Protein S / Q000378:metabolism*; D012016:Reference Values
D011486:Protein C; D017293:Protein S