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.
Uterus Size During Pregnancy: First Trimester. Around 12 weeks pregnant, the uterus is the size of a grapefruit and starts to grow up and out of the your pelvis, but still fits within it. If you are carrying twins or multiples, your uterus will start growing and stretching sooner. Your OB/GYN will be able to feel your uterus by touching your belly.