Fimbriae (common pili) and flagella on the surface of bacterial cells. Left: dividing Shigella enclosed in fimbriae. The structures are probably involved in the bacterium's ability to adhere to the intestinal surface. Right: dividing pair of Salmonella displaying both its peritrichous flagella and its fimbriae.
Relaxin's peak is reached during the 14 weeks of the first trimester and at delivery. It is known to mediate the hemodynamic changes that occur during pregnancy, such as increased cardiac output, increased renal blood flow, and increased arterial compliance.
The most critical period is between 6 to 9 weeks of gestation, but taking warfarin in the second and third trimesters can be also risky. Previous studies have shown that central nervous system abnormalities develop due to usage of warfarin in second and third trimester (secondary to bleeding and formation of blood clots in blood vessels).