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.
Stress or fatigue is suggested to cause a physical reaction within the body, leading to nausea and vomiting. When to expect nausea during pregnancy. Nausea typically starts within four to eight weeks of gestation and is expected to subside between 13 and 14 weeks. However, it can start earlier and can last longer. Also, not every woman will experience nausea the entire duration of the first trimester.