What is the primary hormone responsible for maintaining pregnancy in the first trimester?

The primary hormone responsible for maintaining pregnancy in the first trimester is progesterone. After conception, the corpus luteum produces progesterone, which is crucial for preparing the uterine lining for implantation of the embryo. Progesterone helps maintain a thick, nutrient-rich endometrium, which is essential for the growing embryo and prevents uterine contractions that could lead to miscarriage.

While other hormones, such as human chorionic gonadotropin (HCG), also play significant roles during early pregnancy (for example, HCG helps support the corpus luteum), progesterone is the main hormone that sustains the pregnancy during this critical early stage. Its role in creating a suitable environment within the uterus and maintaining the pregnancy until the placenta takes over hormone production is vital in the first trimester.

Estrogen also contributes to pregnancy maintenance but primarily acts in conjunction with progesterone. Oxytocin, though important later in labor and breastfeeding, does not play a role in maintaining pregnancy during the first trimester.