Final answer:
For a primigravida diagnosed with type 1 diabetes mellitus, regular prenatal care is crucial to monitor and adjust insulin requirements, as insulin needs are variable throughout pregnancy.
Step-by-step explanation:
The importance of regular prenatal care for a primigravida with type 1 diabetes mellitus includes monitoring and adjusting insulin requirements due to the physiological changes that occur during pregnancy. Specifically, insulin needs generally increase in the first trimester due to hormonal changes and the body's growing demand for glucose. However, during the second trimester, some women may experience a decrease in insulin needs as the body adapts to pregnancy. It is in the third trimester, though, when insulin needs significantly increase as the placenta produces more hormones that can lead to insulin resistance, thus increasing the mother's requirement for insulin to maintain blood glucose levels within the normal range. Consequently, option C, which states that insulin needs are variable throughout pregnancy, is the correct answer. It is important for women with type 1 diabetes to work closely with their healthcare team to monitor and adjust their insulin regimen, as maintaining glycemic control is crucial for the health of both the mother and the developing fetus.