Relaxin becomes detectable by week 7-10 and is produced throughout pregnancy. This hormone relaxes the mother's muscles, joints and ligaments to make room for the growing baby. The effects of relaxin are most concentrated around the pelvic region; softening the joints of the pelvis can often lead to pain in the area.

How early does relaxin start in pregnancy?

During pregnancy, relaxin levels are at their highest in the first trimester. At this time it is believed to promote implantation of the developing fetus into the wall of the uterus and the growth of the placenta.

Is relaxin released during menstruation?

Relaxin is crucial to the female reproductive process. Relaxin levels increase after ovulation during the second half of a woman's menstrual cycle, where it is believed to relax the wall of the uterus and prepare it for pregnancy. If a woman does not conceive, levels drop until the next cycle.