About six months after my son was born, he and I were sitting on a blanket at the park with a close friend and her daughter. It was a sunny summer weekend, and other parents and their kids picnicked nearby—mothers munching berries and lounging on the grass, fathers tossing balls with their giddy toddlers. My friend and I, who, in fits of self-empowerment, had conceived our babies with donor sperm because we hadn’t met Mr. Right yet, surveyed the idyllic scene. “Ah, this is the dream,” I said, and we nodded in silence for a minute, then burst out laughing....