My husband and I have different ways in which we contribute to the household. Neither is better, harder, or more valuable. They're different, but equal. Even though I know this, I often disrespect my husband's role by comparing our responsibilities. My husband goes to work while I stay home with Henry. Partly because of that division of labor, partly because of Henry's temperament, and partly because we exclusively breastfeed (meaning no pumping or formula), I end up carrying the most of the burden in regards to the day to day tasks of caring for Henry.
However, my husband cares for Henry in a different way. He makes money for our family, he makes sure our home is clean and babyproofed, he does the laundry, he drives when we are together so I can sit in the backseat with Henry. So, while I feel the weight of taking care of Henry's needs, my husband's responsibilities are different, but equal.
I think one of the greatest areas of stress between partners at the addition of children is about the division of labor. What worked before and was the status quo, no longer works because there are new tasks and a new family member who needs a ton of care and attention. Even if you had an idea of how the home would function before the child's arrival, his or her temperament might force you to adjust your plan. Moreover, I'm a firm believer that nothing can truly prepare you for having a child. Therefore, it's easy to feel tension or distress while navigating the new roles of mother and father and the changing relationship dynamics.
The challenge and the goal is to learn to respect and appreciate the other without devaluing that person's contribution. While our tasks and roles may be different, their value is equal.