Over lunch at our favorite little restaurant, Cathy, my best friend, announced that she was pregnant—and instead of being happy for her, I was stunned to realize that I felt betrayed. Before I had even a second to compose myself, a survival instinct deep within the most primitive part of my brain had taken possession of my emotions. I had a sinking feeling that nothing would ever be the same between Cathy and me. Like it or not, I was competing with the tiny presence in her womb. "Congratulations!" I said, feeling suddenly very lonely. This was not a case of baby envy. When Cathy got pregnant, my own daughter was 12 years old. And some years earlier, after a couple of painful miscarriages, I had decided that I didn't really want any more children. I vividly remembered what it was like to care for a baby—to wake up at three AM, yet not be able to take a shower until three PM—and I was glad that phase of my life was over and done with. No, I was not envious. What I did resent, however, was being presented with a fait accompli. How dare Cathy make a unilateral decision that would affect our relationship! Maybe I would lose her forever. Ah! Separation anxiety is such a primordial emotion, it defies rationality. How needy we all are under our poised, affable facades. And indeed, from that moment until nearly three years later, not only did Cathy and I struggle to make time to get together, but when we did, we strained to find compelling topics of conversation. I had the impression that she was pulling away, no longer chatting enthusiastically the way she used to. Right after the delivery, I went to visit her, but her newborn and I never managed to bond. He would fret and whimper the minute I held him in my arms. And whenever I'd get on the phone with his mother, as if on cue, he'd begin to scream uncontrollably. She would say, "I'll call you back," but she would never find the time to do so. Eventually I stopped reaching out to her. Adults are powerless against the will of a baby who doesn't want to share with others his mother's attention. Let's face it: A brand-new infant car seat strapped into the back seat in a dear friend's car can become a hurdle between two women. No matter how deep the understanding or how long-standing the chumminess, your relationship may be tested when one of you embraces motherhood. A new mother seems distracted, when in fact she is focusing on a complex network of new challenges. As a friend, you get annoyed because she looks at you but doesn't quite see you and doesn't laugh at your jokes anymore. I can only imagine how much worse the feeling of rejection must be for someone who has not experienced motherhood firsthand. Women who are trying to conceive but are denied the joys of childbearing are especially vulnerable when a pregnant friend begins to withdraw from them. It's harder for them to accept that a future mother has to focus inward; it comes with the territory. Try bending like a willow.

All friendships are at the mercy of events beyond our control, which is one of the reasons we cherish their fragile pleasures. In hindsight, I wish I had known it was safe to let go of Cathy when she needed to be left alone. Not clinging to a friend is also part of friendship. Even enduring relationships have their own timetables, with cooling off periods that can last months and even years. As it turned out, my friendship with Cathy was only on hiatus. We were lucky: The birth of her baby heralded what was only a brief interruption.

For many childless women, though, the temptation is to deliberately ignore the overwhelming lifestyle change the birth of a baby has brought into their friend's household. And what a change! My friend Susan is mortified because her former college roommate—a Rhodes scholar who became the lead investment banker for an international merger-and-acquisition team—has decided to stay on maternity leave an extra three months. "Since the birth of her daughter, she only wants to discuss the pros and cons of backpack baby carriers versus swaddling slings," Susan tells me, rolling her eyes. And Carol, a successful graphic designer, recently described her meltdown while baby-sitting in the lobby of a museum for a friend who was in the bathroom filling up a baby bottle with a breast pump. "I can't tell the difference between a pacifier and a teether," Carol recalls, "yet there I was, trying to get a colicky newborn to calm down by pushing him in his stroller back and forth for a full 20 minutes while everyone was staring at me." Maybe there is a good reason why mothers and non-mothers have trouble finding common ground. Only the most devoted buddies are supposed to stick around. Mothering is not for the fainthearted. Mess, chaos, and pandemonium are to be expected. So if you can't take the heat, get out of the nursery. Yet, as out of touch as they sometimes are, baby-bashful girlfriends are a healthy influence on both mother and child. Born in the heady days of early feminism, my daughter was raised among my friends, women for whom liberation was synonymous with solidarity. A number were childless by choice, yet felt compelled to support peers who, like me, were single with a baby in tow. These liberated girls would bring over their knitting for the evening and, while I did the dishes, show my kid how to purl. From these impromptu "aunts," my daughter learned something I couldn't have taught her on my own: that she belongs to a large tribe of generous and multitalented women. In the long run, the presence of a child can be an opportunity for girlfriends to get closer to each other. Cathy and I didn't drift apart forever. When her son was three, she emerged from mental hibernation: One morning (perhaps because she'd had an almost normal night of sleep, at last), she woke up and was her old self again. She called me and we resumed our relationship with renewed energy. Today we live on different coasts, but we are very close. We are linked by a common history—that of our friendship. Together we have grown as much as, if not more than, the children we have nurtured over the years.