Birth and the survival of the fittest

Everyone knows that evolution is based on the principle of “survival of the fittest.” What does that mean for childbirth?

It means that by definition not everyone survives. Lots of people die. In the case of childbirth it means high levels of neonatal and maternal mortality.

So contrary to the inane babbling of NCB and homebirth advocates that women’s bodies are perfectly designed to give birth, no one’s body is perfectly designed for anything. There is a tremendous amount of genetic variation, there are many competing environmental pressures and the environment can change over time. Simply put, human existence is a competition and many drop out and die along the way. That applies to childbirth just as to any other aspect of human existence.

For example, there is tremendous genetic variation to the onset of labor and there are risks and benefits to each variation. Consider the onset of labor. The range of normal is extremely wide. In human pregnancy (average length 40 weeks) labor can start normally anywhere from 38-42 weeks, and onset is not restricted to the normal range. Premature birth is quite common and post mature birth is hardly rare.

Contrary to the nonsense spouted by NCB and homebirth advocates that babies “know” when to be born, there are advantages and disadvantages to birth at any possible gestational age. Babies born at earlier gestational ages are smaller and therefore more likely to fit through the mother’s pelvis. Yet babies born at earlier gestational ages will be less likely to have mature organ systems, and therefore more vulnerable to illness and death. On the other hand, babies born at later gestational ages are more robust, but they are also larger and might not fit through the mother’s pelvis or might outgrow the ability of the placenta to supply them with oxygen, and die before labor even begins.

And birth doesn’t depend only on the baby. It also depends on the mother. The maternal pelvic dimensions are determine by a wide array of genetic factors, each independent of the others. Moreover, a pelvic structure that is beneficial for birth may be suboptimal for maternal survival in the non-pregnant state. A wide maternal pelvis is ideal for childbirth, but limits maternal mobility and therefore the ability of the mother to outrun predators and to keep up with her tribe.

It isn’t simply the expulsion of the baby at birth that is affected by maternal genetic variation. If the mother’s blood type and the babies blood type differ (and both are determined independently), the mother’s immune system can attack the baby’s blood cells and kill the baby.

Pregnancy produces a variety of metabolic changes in the mother, some of which may be deleterious to the baby, the mother, or both. Gestational diabetes increases the risk of neonatal complications and the risk that the baby will be too big to fit through the maternal pelvis. Pre-eclampsia and eclampsia can kill the baby, the mother or both through a series of complex metabolic changes that affect everything from blood pressure, to blood clotting, to maternal seizure threshold. Just as subclinical sickle cell trait confers an evolutionary advantage in surviving malaria, but clinical sickle cell disease is a killer, subclinical variations of pregnancy complications probably also confer an evolutionary advantage, but clinical manifestations can and do kill.

Consider something as common as postpartum hemorrhage. The most common cause of postpartum hemorrhage is uterine atony, failure of the uterus to contract strongly after the placenta has been expelled. Prolonged labor is a risk factor atony, and the length of labor is determined not merely by maternal factors like the strength of contractions and the size of the maternal pelvis, but by fetal factors like the size of the baby and its position as it enters the pelvis. It is the interplay between these maternal and fetal factors that determine whether a fatal hemorrhage will occur after birth, not some mystical “perfection” of the process that can be relied upon to provide the desired outcome.

Survival of the fittest means exactly what it sounds like: only the fittest will survive and the rest will die. Being the “fittest” in a given environment depends on a complex interplay of multiple genetic factors, each of which is independent of the others. Just like a human being isn’t “perfectly designed” to outrun every predator, every human being (mother or baby) is not perfectly designed to survive pregnancy and childbirth.

Human beings have survived and thrived thus far because of technological interventions. We can’t outrun every predator, but we can create spears to kills predators from a distance and we can make fire to ward off predators that we cannot see in the dark. I haven’t noticed anyone claiming that authentic human existence requires returning to the savannah, giving up fire, and putting aside our spears.

We cannot control climate, or our vulnerability to severe climatic conditions, but we can create clothes to hold body heat, houses to shelter us, and central heating to warm us. I haven’t noticed anyone claiming that authentic human existence requires shedding our clothes, leaving our houses and huddling in caves.

We cannot depend on every baby to fit through a maternal pelvis, every pregnancy to last for the optimal length of time, and every mother to withstand the metabolic extremes that may be caused by pregnancy. Yet I have heard NCB and homebirth advocates prate that authentic childbirth requires vaginal delivery, “unhindered” labor regardless of timing, and an acceptance of every maternal metabolic change no matter how deranged.

The hallmark of human evolutionary success is the development and deployment of technology. In this environment, that’s what makes people fit. Rejecting that technology, and demonizing it as unnecessary and inauthentic is the ultimate in foolishness.

The fittest mother is not the one who rejects technological interventions; the fittest mother is the one who employs any and every technological intervention that can potentially enhance her child’s survival. Anything less is the intellectual equivalent of prancing around naked in a snowstorm while rejecting houses, central heating and even fire as unnecessary technological “interventions.” It’s extremely painful and a quick way to an unnecessary death.