CBSE Class 12-science Answered

In case of human females, if the ovum is fertilised and pregnancy occurs, the corpus luteum persists and is transformed into corpus luteum graviditatis (verum) or corpus luteum pregnancy. It remains in the ovary for 3-4 months, during which it secretes large amount of progesterone with small quantity of estrogen, which are essential to maintain pregnancy. After 3-4 months, the placenta begins to secrete these hormones and the corpus luteum degenerates.

Relaxin is secreted by the corpus luteum during the initial period of pregnancy. Later on, it is secreted in large quantities at the time of labour by placenta and mammary glands. Relaxin helps to soften the cervix and relax the pelvic ligaments during childbirth.