Protein is essential during pregnancy primarily for fetal tissue growth. It provides the necessary amino acids required for the development of fetal organs, muscles, and overall cellular structure. Adequate protein intake supports the rapid cell division and differentiation happening in the fetus. Additionally, protein contributes to the growth of maternal tissues such as the uterus and placenta. Unlike energy storage or calcium absorption, the key role of protein is to build and repair tissues, making it critical for healthy fetal development.

Reference: Maternal & Child Health Nursing, Adele Pillitteri, 7th Edition.