What is the role of human placental lactogen during pregnancy?

Human placental lactogen (hPL), also known as human chorionic somatomammotropin, plays a significant role during pregnancy primarily by promoting maternal metabolic adaptations that ensure adequate fetal growth. One of its key functions is to antagonize insulin effects, which leads to an increase in glucose availability in the maternal circulation. This action enhances the supply of glucose to the fetus, which is essential for its growth and development.

As pregnancy progresses, hPL levels rise, which corresponds to the increasing demands of the growing fetus. This rise in hPL not only supports the energy needs of the fetus by modulating maternal glucose metabolism but also facilitates lipolysis, encouraging the use of fatty acids for maternal energy. Further, it can influence mammary gland development in preparation for breastfeeding.

The other options provided do not accurately reflect the role of hPL. For instance, the fluctuating trend of hPL levels does not encompass a decrease over time throughout pregnancy, nor is the emphasis on its categorization as a protein sufficient to convey its functional role. Additionally, while hPL does increase as pregnancy advances, the choice that specifically highlights its mechanism of antagonizing insulin to enhance glucose availability is the most pertinent and captures the essence of hPL's function in supporting fetal