Final answer:
The placenta secretes two primary hormones, estrogen and progesterone, which are essential for maintaining pregnancy and preparing the body for childbirth.
Step-by-step explanation:
The two hormones that the placenta secretes are estrogen and progesterone. These hormones are critical for pregnancy, as estrogen maintains the pregnancy, promotes fetal viability, and stimulates tissue growth in the mother and fetus. Progesterone plays a role in preventing new ovarian follicles from developing, suppressing uterine contractility to prevent preterm labor, and later allowing for the intensification of uterine contractions that lead to childbirth. It is also important to know that the placenta produces the hormone hCG, which supports the corpus luteum and influences the male fetal gonads to secrete testosterone.