Relaxin levels in the circulation rise after ovulation, during the second half of the menstrual cycle. At this stage it is thought to relax the wall of the uterus by inhibiting contractions, and it also prepares the lining of the uterus for pregnancy.

When do your ligaments start loosening in pregnancy?

This common — though uncomfortable — sensation is your body's way of stretching to accommodate your growing uterus. Many women start feeling it around week 14 of pregnancy, but it can strike at any time from the second trimester on. Round ligament pain isn't unusual in pregnancy, and it's often temporary.

How long does your body produce relaxin?

In humans. In females, relaxin is produced mainly by the corpus luteum, in both pregnant and nonpregnant females. Relaxin levels rise to a peak within approximately 14 days of ovulation, and then decline in the absence of pregnancy, resulting in menstruation.