Which hormone is primarily responsible for the maintenance of pregnancy?

Progesterone is a crucial hormone for maintaining pregnancy. It plays a vital role in preparing the endometrium (the lining of the uterus) for a fertilized egg to implant and thrive. After fertilization occurs, progesterone helps maintain the uterine environment, preventing contractions that could disrupt the newly formed placenta and embryo. It also promotes the growth of blood vessels in the endometrium, ensuring a sufficient blood supply for the developing fetus.

Throughout the first trimester of pregnancy, progesterone levels remain elevated to support the pregnancy until the placenta can take over hormone production. Its action is fundamental in preventing premature labor and ensuring that the body can sustain the pregnancy until the fetus reaches viability.

Other hormones, while important in various aspects of reproductive health and childbirth, do not primarily focus on the maintenance of pregnancy in the same way as progesterone. Estrogen contributes to the development of fetal tissues and regulation of other hormones. Oxytocin plays a significant role during childbirth and lactation, stimulating uterine contractions and milk ejection. Relaxin helps to soften the cervix and relax pelvic ligaments but does not maintain the pregnancy itself.