Book Club: The Fourth Trimester: Understanding, Protecting and Nurturing an Infant Through the First Three Months

by Sarah Gilbreath

The-Fourth-TrimesterThis month, the P&N Book Club delves into the science behind an infant’s first few months of life. In The Fourth Trimester: Understanding, Protecting, and Nurturing an Infant Through the First Three Months, long-time medical journalist Susan Brink details the importance of the fourth trimester as the final phase of development, providing insight in how being born must feel to a baby and sharing new research on the this crucial time period’s impact on health later in life.


P&N: You mention that your inspiration for the book came from witnessing the reactions of friends and family members when they first became parents, and remembering your own experience. If you could go back to the moment you became a mother, what advice would you give yourself?

SB: That question takes me way back, some 43 years. Not only did my book not exist as a resource to help prepare new parents, but also the science behind my book had not yet been developed. The advice of parents, in-laws, friends and relatives was all over the map, in keeping with the times, and much of it was based on the belief that you could “spoil” a baby by doing what the infant wanted. That was bad advice.

So I think the number one piece of advice I’d give myself, if I could run life’s reel backwards to that moment in time, would be: Don’t worry. You cannot spoil a newborn. Do what the baby wants you to do when she wants you to do it. The number one job during the first three months of my baby girl’s life, I’d counsel myself, is to be a loving, careful observer of all the cues and signals she is sending that tell me what she wants and needs. I’d say to myself that biology has designed my baby to communicate her needs. In my chapters on the senses—vision, hearing and touch—I describe those communication methods. And then I’d tell myself to look for those cues, and respond as lovingly and immediately as possible. Don’t worry about spoiling her. Feed her, let her sleep and be awake, on her unique schedule. Comfort her when she cries, even during those frustrating times when you cannot figure out why she’s crying.

An infant, during the fourth trimester, is not neurologically or emotionally prepared to “cry it out,” so stick with her through her distressing times. You won’t be spoiling her. Indeed, you’ll be giving her the important message that you’re there for her, even when you don’t completely understand her distress. Pay very close attention all the time. And because this is such a demanding time for a new mother, ask for help from your spouse, partner, family members and friends and don’t hesitate to accept any and all help that is offered.

P&N: How is this fourth trimester different for premature babies? Do they experience it, as well as regular development, simultaneously?

SB: My book is primarily written with healthy, full-term infants in mind. Premature babies need the care and guidance provided by pediatricians based on the unique health needs of preemies. By definition, a premature infant can be born as few as three weeks too early (or 37 weeks gestation) or as extremely premature as 15 weeks too early (or 25 weeks gestation.) New technology, such as MRI scanning, has shown that brain development of premature infants is quite different from that of full-term babies, with many parts of the brain smaller and less developed. And, of course, the amounts of prematurity, as well as the reason for the premature birth are factors in how well the infant will do in the long term.

But though The Fourth Trimester is about early development of full-term infants, science has learned a lot from the needs of premature babies. For example, we know that colostrum, the first breast secretion before a mother’s milk comes in, provides a measure of protection against infection for all infants—but the antibody called secretory immunoglobulin found in colostrum is particularly helpful to premature infants in fighting off infection.

And most of what we know about pain in full-term infants came from research on premature infants in neonatal intensive care units. Preemies often need a lot of medical procedures involving needles and IV tubes. Researchers found that even very premature babies feel pain, and that that pain can be safely controlled. Medical science went on to prove that if we can control pain even in premature babies with numerous health problems, we can and must also control pain in healthy, full-term infants.

And we’ve learned from premature infants that gentle skin-to-skin touch—stroking, or soft massage—helps them gain weight and develop bone mass. It’s a life-enhancing lesson that benefits full-term infants, as well.

P&N:  You frequently mention the circuitous route of the birth canal. Are there any positions that might make it more straightforward, and therefore easier for the mother and baby?

SB: The birth canal is circuitous whether lying down, squatting, kneeling or in a more upright, vertical position. That’s because, regardless of position, the infant’s head and body must go through a series of rotations in response to the dimensions of its head and shoulders in relation to the mother’s pelvic dimensions. Studies have found that differences in blood loss, time spent pushing, and duration of labor were statistically insignificant, as was the Apgar score of the newborn, regardless of the birthing position of the mother. Some studies have shown that a more upright position helps the mother’s pushing work with gravity for a slightly shorter (say, three minutes or so) delivery time—again, statistically not significant. Though differences are slight, there is no reason that a woman shouldn’t give birth in the position that is most comfortable or desirable for her. She should make sure she has a cooperative medical provider who will accommodate her wishes.

P&N: Are any of the studies you cited still ongoing? If so, have there been any new advances or proposed theories since completion of the book?

SB: There is no stopping science, or the curiosity and creativity of researchers. I looked at hundreds of studies, many of which will provide the hypotheses for future research. One example is new research on hearing. It showed that, just as the early glimpses of vision begin to build the neural architecture that allows the brain to interpret images, every early sound is also creating neural architecture that allows the brain to sort out language and the cacophony of the world around us. That new development in how scientists understand hearing has already led to research looking at potential long-term consequences of ear infections in infants. Could it be responsible, some researchers wonder, for adults who have difficulty sorting out words when conversations are going on around a crowded dinner table, or in a busy, noisy room? And are there therapies that can help youngsters who have a history of multiple ear infections?

Brain research into the infant brain is in its own infancy, and it is only recently that neuroscience has the tools—like functional magnetic resonance imaging, CT scans and PET scans—that create three-dimensional images of the brain. That allows scientists to examine the brain’s chemical composition, electrical transmissions and blood flow.

A report in 2000 by the National Research Council and Institute of Medicine, “From Neurons to Neighborhoods: The Science of Early Childhood Development,” was the impetus behind the birth of an organization called Zero to Three, an organization that focuses on development during the critical first three years of life. Parents can now go to their site ( and find an interactive tool to help explain how the infant and growing brain is processing sight, sound, and touch.

Researchers around the world are interested in childhood obesity. Recent studies suggest that breastfed and formula-fed babies have about equal risks for later obesity. But research may now focus of timing of feedings. Are mothers who try to feed infants more that they might want—often in an attempt to try to make them sleep longer–inadvertently teaching them to overeat? We don’t know, but it has the attention of some researchers.

P&N: What is the one piece of advice you hope readers take away from the book?

SB: First, I think the perfect time to read The Fourth Trimester is when a couple is planning or expecting a baby—while they still have a little time to read—so they can learn what recent science has to say about what it’s really and truly like to be a newborn baby who is suddenly plunked down in this messy, chaotic world of ours.

With that understanding, I’d advise new parents, or grandparents and other loving friends and relatives, to muster up their empathy do all that they can to perceive the world through the baby’s eyes and senses. That will make it easier for you to provide the patient, loving, constant attention that you’ll need in order to give your baby the best possible start. Watch, listen and learn from this marvelous new human being.

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