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.
As the pregnancy grows it releases the pregnancy hormone called human chorionic gonadotropin (hCG) into the maternal blood. This hormone can be detected one week after implantation (28 days from the beginning of the menstrual period and 2 weeks after ovulation) in the blood or urine. So, pregnancy officially begins at the time of implantation but is usually not detectable until the pregnancy hormone shows up in the blood and urine.