when does relaxin start being produced during pregnancy
Relaxin In females, relaxin is produced mainly by the corpus luteum, in both pregnant [1] and nonpregnant[1] females; it rises to a peak within approximately 14 days of ovulation, and then declines in the absence of pregnancy, resulting in menstruation[citation needed]). During the first trimester of pregnancy, levels rise and additional relaxin is produced by the decidua. 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. It also relaxes other pelvic ligaments.[6] It is believed to soften the pubic symphysis.
Corpus luteum The introduction of prostaglandins at this point causes the degeneration of the corpus luteum and the abortion of the fetus. However, in placental animals such as humans, the placenta eventually takes over progesterone production and the corpus luteum degrades into a corpus albicans without embryo/fetus loss.