Making Babies: The Science of Pregnancy (review)

Motivated by his wife's challenging pregnancy with their first child, David Bainbridge has written an engaging and informative book targeted at an educated lay audience. Pregnancy and birth are inherently interesting topics to most of us because, despite major scientific and clinical advancements in understanding the processes, they are still cloaked in mystery and produce awe in those who experience them. Bainbridge sets out to answer what he calls the five big questions of pregnancy, around which he organizes this book. In each of the chapters he presents an overview of the historical contributions of some of the world's best known biologists (e.g., Gregor Mendel in Chapter 1, William Harvey in Chapter 2, Ernst Haeckel in Chapter 3, and Sir Peter Medawar in Chapter 4) as well as contemporary issues that inspire great debate (e.g., designer babies, stem cell research, extrauterine pregnancy).

Why do we reproduce the way we do? In the first chapter Bainbridge tackles the age-old question of why we (and most other vertebrates) reproduce sexually when so many other organisms get along fine without sex and, furthermore, are able to pass along virtually 100% of their genes each time they reproduce. His efforts to answer this question weave together historical threads from Mendel's work, parthenogenetic lizards, Dolly the sheep, the virgin birth of Jesus, and designer babies. Readers are introduced to basic Mendelian genetics, sickle cell anemia, genetic imprinting, the major histocompatibility complex (MHC), an unusual case of a boy who is a male/parthenogenetic chimera, anisogamy, "mitochondrial infestation," and maternal control of embryo formation. Most of the information in this chapter has been simplified so that, in the end, the reader comes away with a pretty good answer to why we have sex, even if it does include the somewhat unpalatable idea that sex helps us to shed parasites. Along the way there is a lot of engaging information about human reproductive biology at the early stages of pregnancy.

How does a mother "know" she is pregnant? To the nonscientist, this may not seem to be a very important question (after all, many seek the answer from their physicians or home pregnancy tests). However, what Bainbridge is addressing, of course, is the fact that the embryo is a foreign body to the maternal immune system so rejection would be more expected than retention. His historical focus in this chapter is William Harvey, perhaps best known for his contributions to understanding the circulation of blood but who also made significant contributions to early understandings of conception. Although he did not have the technological ability to detect sperm and egg, he concluded that both mother and father contributed to the development of an embryo and that internal gestation required an entirely different relationship between mother and fetus than that in animals that lay eggs. Furthermore, the primary way of recognizing pregnancy (then and now) was the cessation of menstruation, so he knew that some sort of communication must occur between mother and fetus to suspend normal cycles in the mother long before physical signs of pregnancy emerge.

Harvey's focus on the mother was an entirely new way of looking at pregnancy, and it is one that has received a lot of scientific and clinical attention in the intervening centuries. But how does the embryo "tell" the mother that she is pregnant so that her system responds appropriately? We now know that hormones are involved, but these were not part of the explanation until the early 20th century.

The rest of this chapter discusses the development of RIA, the roles of various reproductive hormones, ovarian cycles and menstruation, the life (or not) of the corpus luteum, endometriosis, pseudopregnancies, interferons, pregnancy tests, and morning sickness. One tidbit I found particularly interesting is that babies that cause serious morning sickness in their mothers tend to like the taste of salt.

How is a baby put together? Ernst Haeckel is the historical hero of this chapter, primarily for...