Giving birth in the early 1990s in an Upper East Side hospital remains, in my memory, a primal experience. But as Tina Cassidy describes it in “Birth” (Atlantic Monthly Press, 312 pages, $24) — and she is persuasive — our choices about where, how, and even when to give birth are guided, if not limited, by a culture that shapes us much more than we realize. Most Western births these days take place in hospitals, though before the 20th century they usually took place at home. And the increasingly common induction or scheduled C-section means that we can choose the day and very nearly the hour at which we give birth.

The impression that we are in charge means that we are astonished when things don’t go as we expect (or think we have planned). Ms. Cassidy’s experience of giving birth and her surprise at her poor outcome — an emergency C-section followed by not one but two serious infections — caused her to explore first her own family history and then the culture’s. The result is rather eye-opening for women who grew up thinking we were taking over: that reclaiming control over our bodies meant we would surely enjoy a calm, safe labor and delivery. The truth is that childbirth is still painful and risky, even for women who receive good medical care. As Ms. Cassidy puts it, “The arrival of a healthy baby is truly a miracle.”

She begins by placing the physiology of birth firmly into the context of human evolution. Because we walk upright, our pelvises are small compared to those of, say, apes. And because we have well-developed brains, our craniums are relatively large. The human female pelvis has evolved to be widest at the top from side to side, but widest at the bottom from front to back. This means that in order to be born, the human baby must twist in the birth canal. Yet modern nutrition means that babies are becoming larger. While modern nutrition (OK, fast food) is also making mothers larger, there is not enough genetic variation in the population for the development of larger birth canals. This limit should alert us to the fact that even as some medical risks decrease, our culture causes new risks to arise.

The story Ms. Cassidy tells from here, as she reviews the change to doctors from midwives, the move to hospitals from homes, and the advances in pain relief, is one of medical developments largely, but not entirely, conceived by men. That men were involved at all was a change; until the rise of doctors in the early 19th century, in most places, childbirth had been strictly a feminine domain. Changes in practice were first adopted by (or imposed upon) women giving birth, then rejected by later generations of women, and sometimes by their doctors. The fact that many innovations — lying down instead of using a birthing stool, the use of forceps in delivery — didn’t always make things better for women or babies seems not to have stopped some women from asking for them.

Of course, many of these innovations meet real needs. Cesarean sections were first used to remove a stuck or deceased fetus before it could poison its mother. For those inclined to the gruesome, Ms. Cassidy provides some rather vivid descriptions of some of the earlier techniques. She points out that, contrary to myths surrounding the birth of Julius Cesar, the surgery was probably first performed in the 15th century. The largest initial problem with the operation was the risk of infection. Once that was solved, more or less, with modern methods of infection control in the early 20th century, C-sections became much more common.

Moneyed urban women have been opting for C-sections for a century. Ms. Cassidy writes that many doctors now prefer them for themselves or their partners, even for uncomplicated pregnancies. And there are often medical reasons for a C-section, though Ms. Cassidy does a good job of showing why one of them, “failure to progress,” may be based on myth. Yet Ms. Cassidy writes that even before recently reported research suggested that death rates were higher for newborns born by C-section, some commentators found the increasing numbers of C-sections to be problematic. Exploring why these contradictory views exist — conflicting statistical studies? Lack of communication between doctors and patients? Too much communication between expectant mothers with not enough information? — would have made for a more satisfying book. But Ms. Cassidy simply concludes that the issue can’t be resolved.

The treatment of the pain of childbirth is another place where cultural developments due to male doctors were first adopted, and then rejected by their female patients. Before the mid-19th century, midwives offered calming words to alleviate pain. Then doctors started using chloroform, or twilight sleep (the use of a combination of scopolamine and morphine to render women in labor semiconscious, so that they didn’t remember the pain) or general anesthesia to eradicate it. In the 1970s, women began insisting on “natural” childbirth, refusing the anesthesia their mothers had used. It’s doctrine now that obstetricians send their patients for childbirth education classes. My class, at least, carried the subtext that it’s better for mother and baby if labor stays drug-free — but then why do our doctors keep appearing in the delivery room asking if we’re ready for the epidural, the most recent development in pain relief? We’re getting a mixed message.

This uneven book is not helped by its structure, which is less chronological than topical, and can feel repetitive and occasionally padded. But Ms. Cassidy offers several helpful chapters, including an exploration of the evolving role of fathers in the delivery room, and a sprightly survey of postpartum issues. Her book has real value for women who want to understand why the reality of giving birth didn’t match their careful plans and expectations.