What is the primary role of the umbilical cord during pregnancy?

The primary role of the umbilical cord during pregnancy is to connect the fetus to the placenta for nutrient exchange. The umbilical cord contains blood vessels that facilitate the transfer of oxygen and essential nutrients from the mother to the developing fetus, while also removing waste products from the fetal circulation. This critical connection supports the fetus's growth and development throughout the pregnancy.

While the other options present several functions related to pregnancy and fetal development, they do not accurately capture the primary function of the umbilical cord. The umbilical cord does not serve as a protective barrier; rather, the amniotic sac provides protection. Although the placenta can generate some hormones important for maintaining pregnancy, the umbilical cord itself does not have a role in hormone production. Lastly, maintaining fetal posture is influenced more by the amniotic fluid and the space in the uterus rather than the umbilical cord itself. Thus, the correct answer highlights the vital life-supporting function of the umbilical cord in connecting the fetus and placenta for nutrient and waste exchange.