In the placenta's trimester-specific production, which hormone is primarily produced during the second trimester?

• A. hCG
• B. Estrogen
• C. Progesterone
• D. hPL

Answer: (B)

In the placenta, hormone production shifts as pregnancy progresses. Early on, hCG from the placental tissue helps sustain the corpus luteum so it continues producing progesterone and estrogen. As the placenta matures, estrogen becomes the dominant placental hormone in the second trimester. This rise in placental estrogen supports expansion of the uterus, increases uteroplacental blood flow, and aids fetal development. Progesterone remains essential to maintain the pregnancy, but the hallmark change in the second trimester is the placenta taking over estrogen production. Human placental lactogen (hPL) rises more noticeably later in pregnancy to influence maternal metabolism, and hCG declines after the first trimester, so they’re less characteristic of the second trimester compared with estrogen.