Which of the following secretes the hormone, relaxin, during the later phase of pregnancy?

The hormone relaxin is produced during pregnancy to help relax the pelvic ligaments and the cervix, preparing the birth canal for delivery.

In the early stages of pregnancy, the primary endocrine organ is the corpus luteum, which forms from the ovarian follicle after ovulation. It is well‑known for secreting progesterone to maintain the uterine lining.

As pregnancy progresses into the later phase, the corpus luteum continues to function and, in addition to progesterone, begins to secrete relaxin. This secretion peaks in the second trimester and contributes to the softening of the uterine musculature and the relaxation of the pelvic joints.

Other structures listed—such as the foetus, the uterus itself, and the Graafian follicle—do not serve as the main source of relaxin during this period. The uterus may respond to relaxin, but it does not produce it, and the Graafian follicle has already transformed into the corpus luteum after ovulation.

Therefore, among the given options, the correct source of relaxin in the later phase of pregnancy is the corpus luteum.