Yes, pregnancy is a unique experience. For some women it goes away magically after birth; others have lasting physical and mental changes. Whether this is the most profound experience imaginable in human existence is arguable, though I'm inclined to think it's pretty powerful.

However, the "asymmetry" of pregnancy and child birth is neither fundamental nor permanent for the issue under discussion: sharing the load in child raising more equally, and fathers getting to spend more time with their babies. After breastfeeding is over, fathers are perfectly capable of raising a kid without a mother. It's not magic.