How was our life before birth and what we did in mother’s womb? Writes Ian Linden
A new-born baby’s first cry: a sound that signals its triumphant transition from the fluid world of the womb to the air of the outside world, from complete dependence on the placenta for oxygen to independent breathing. A transition, for which nine long months of pregnancy have prepared, achieved during the first seconds and minutes after birth. Almost miraculously, the new-born child instantly adapts to life in another world.
Towards the end of pregnancy, the baby increasingly exercises its breathing muscles, taking in and expelling amniotic fluid from its trachea. After the umbilical cord and artery are tied off, with its first breath, the arteries in the baby’s lungs dilate and their air sacs are ventilated as the oxygenated blood flow switches to the pulmonary artery. To change the blood flow, a little flap-valve in the foetal heart, and a small duct between the major pulmonary artery and aorta close, one immediately, the other over a few hours, sending all the blood through the lungs at each heart cycle. To grow and develop successfully, to reach this point, the baby has depended on its surrounding environment.
Peter Nathanielsz has recently updated and expanded his book, Life Before Birth: The Challenges of Foetal Development (Life Course health Press). Professor Nathanielsz is an internationally respected expert in foetal physiology. His original work, translated into fourteen languages, received accolades from around the world. Written in clear English with helpful diagrams and illustrations, an excellent glossary and index, the book helped to establish a trend: making scientific research accessible to the non-specialist, continued today in the BBC’s science broadcasting. He keeps to his promise to avoid speculation and provide only factual information that is backed up by credible and tested research. In this second edition the story of foetal development is filled out with evidence from the last thirty years’ scientific researches. And what a story it is!
The Human Genome Project, unravelling the make-up of our genetic code, our genotype, completed in 2003, was just getting underway in 1992 when the first edition of Life Before Birth was published. This recent edition includes fascinating data from molecular biologists on the complex process of how particular genes are “expressed”, that is step by step how they provide instructions for building proteins and the body’s different cells and tissues, controlling and regulating the events that take place during the development of the placenta, embryo, foetus and new-born baby. For example, a single gene, SRY, on the exclusively male Y chromosome provides instructions for the primitive gonad to become a testis.
Experiments on, rats, mice, sheep, and rhesus monkeys have yielded many of the results applicable to human development. Ultrasound, MRI (Magnetic Resonance Imaging) scans and other technological advances have played their part. Studies on sheep, for example, have shown the sensitivity of the foetus to sound and light. Foetal response to sound begins and grows at two-thirds through human pregnancy. If the mother whispers in one ear of her new-born baby and the father in the other, the baby will invariably turn towards its mother; in utero it has heard her voice most often.
But the core theme of the book is in the title: “challenges to foetal development”. We are susceptible to a range of intra-uterine experiences. As a result of current or past environmental changes, conditions in the womb may deviate from a normal range, with resulting changes in gene function. Analysis of such changes in gene function are a growing area of study known as epigenetics. And some of these changes predispose the individual foetus to ill-health in later life.
Over the last thirty years, understanding has grown of how responses to challenges experienced in the womb may, as the book says, “alter the development of foetal organs, changing their functional capacities in ways that can persist across the life-course”. This alteration of normal development is known as “developmental programming”. In other words, how our inherited genotype plus environment creates, for better or worse, our phenotype, the sum total of our unique physical and behavioural characteristics.
Smoking, parental obesity or malnutrition, advanced parental age, alcohol, “recreational” drugs can all cause potentially measurable negative changes in foetal development, with consequences in later life such as hypertension, obesity, diabetes, and cardiovascular problems. Changes in developmental programming can even accelerate ageing, a remarkable story told in later chapters of the book. Despite the womb being an extraordinary nurturing organ, damaging molecules with potential to harm mothers cross the placenta, and by entering the foetus’s own developing gametes (sperm and eggs), to harm their children and grandchildren. Cocaine in the mother’s blood can harm the foetus by shutting down blood supply to the uterus without having to pass through the placenta.
It is not only the mother’s physical condition which affects the child. For example, recent Canadian research on male mice has shown how paternal obesity acts not only through poor sperm quality but also through the impact of seminal fluid/plasma on the biochemistry of the uterine lining. Mating with high-fat males produces offspring with poorer glucose tolerance in adult life and suggests damage to the energy-generating units in the offspring’s cells, the mitochondria, transmissible to the next generation.
In a final chapter, Lucilla Poston, Professor of Maternal and Foetal Health at King’s College London, explains the importance and practical implications of our current knowledge of epigenetics. Economic and social disadvantage affect future as well as present generations. Even from before conception foetal, neonatal and later health all depend to a significant degree on good diet, parental health and fitness. Another powerful reason for government to “level up”. No-one pretends that will be easy. But there are simple, achievable policies, such as promoting dietary supplements. In one survey “of more than 131,000 women planning pregnancy in the UK, less than one third were taking folate supplements” (folic acid prevents spina bifida and is essential for the body to make DNA).
Often the stuff of our contemporary “culture wars”, discussions about the beginning of life — with all its intricate self-regulation and complex bio-chemistry ignored — are increasingly fraught. Views are mainly expressed in the assertive language of conflictual rights, with little acknowledgement of duties, whether personal or social, and negligible concern for the significance of hard-won medical scientific knowledge on which health and lives depend. Nathanielsz brings four precious assets to his story: a well-honed scientific mind, wisdom, clarity of expression and above all facts.
To say a book is a must-read is a cliché. But Life before Birth really should be widely read. This new edition is a treasure trove of material suitable for inclusion in school curricula. Poston cites as exemplary the University of Southampton’s “Life-lab” project which aims to teach secondary school children about biology and health from womb to tomb.
Finally, no disclaimer this, at secondary school Nathanielsz and I had the same inspiring biology teacher. We can both vouch for the importance of a first-rate science education for everyone. Life before Birth shows how it is done. Our generation owes the next not only good health but the awe and wonder that insights into foetal life evoke.
