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.
With the first baby most moms normally recognise the feeling between 16 & 20 weeks and the overall average seeming to be between 15 and 18 weeks. Experienced moms normally feel the baby earlier then first time moms. Others (like daddy) will usually begin to be able to feel baby kick around the end of the 2nd trimester.