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.
Also, when switching, full protection from pregnancy begins after 48 hours if the first dose of the progestin-only contraceptive is taken on the first day of the menstrual period. If the birth control is begun on other days, full protection may begin 3 weeks after you begin taking the medicine for the first time.