Heterozygote carriers of mutations in the F11 gene, encoding Factor XI, have normal coagulation by thromboelastography during pregnancy

•Comparison between F11 mutation carriers and presumed to be normal pregnant women.•F11 mutation carriers had reduced FXI activity levels.•thromboelastography revealed no clinically significant differences between groups.•No pregnant women in either group experienced an anesthetic complication. Evidence to guide clinical decision-making in pregnant women who are usually asymptomatic, but identified as heterozygote carriers of F11 mutations, is lacking. We hypothesized that women identified on prenatal screening as heterozygous for a mutation in the F11 allele would have minimal evidence of an in vitro coagulation abnormality. We prospectively enrolled women identified by prenatal screening as F11 mutation carriers and pregnant women who were presumed to be normal as controls. We collected blood during antepartum visits or at presentation for delivery and assessed Factor XI (FXI) coagulant activity level, as well as whole-blood coagulation, by thromboelastography. F11 mutation carriers had lower serum FXI activity levels than controls (51.2 ± 8.5% vs 94.1 ± 19.4%; P