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How do the ovaries support pregnancy during its early weeks?

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Close-up of a home pregnancy test device showing a blue plus sign in the result window, indicating a positive result for pregnancy. — pregnancy Devices for individual use at home detect pregnancy by measuring levels of the hormone human chorionic gonadotropin (hCG) in urine.

During the early weeks of pregnancy, the ovaries support the developing embryo primarily through the activity of the corpus luteum, a glandular structure that forms at the site of the ruptured follicle following ovulation.312

The corpus luteum secretes progesterone and estrogens, which are essential for maintaining the pregnancy. These hormones prepare the uterus for implantation, promote the proliferation of the endometrium, and inhibit uterine contractions that could otherwise lead to the rejection of the embryo. Additionally, these hormones act on the pituitary gland to suppress further ovulation, ensuring undisturbed fetal development.32145

To sustain this function, the developing placenta produces human chorionic gonadotropin (HCG), which prolongs the life of the corpus luteum. By approximately the 70th day of pregnancy, the placenta is capable of producing sufficient progesterone and estrogen to take over these functions, rendering the corpus luteum no longer essential for the maintenance of the pregnancy.352