Stress and Pregnancy: How It Affects an Unborn Child's Brain

The Stressed Pregnant Mother

Source: Lin Shao Hua/Dreamstime

All parents want to have healthy and happy children. When pregnant, they will make every effort to eat well, take the proper supplements, and avoid recreational drugs, alcohol, and cigarettes.

Few of them are unaware of the destructive power on their unborn children of parental stress.

While most people understand what the word stress means, the concept is quite difficult to define.

For our purposes, stress denotes both the internal and external demands that we face to accommodate change. Stress becomes negative when adaptation or coping mechanisms fail. However, stress is very subjective. For me, what may be horrifying to even contemplate may be savored by another, like bungee jumping.

Stress Hormones
One group of stress hormones is called catecholamines, and they consist of adrenaline and nor-adrenaline. These are manufactured in the adrenal gland's inner core (the medulla), a small gland that sits on top of the kidneys. So, when a person feels stressed, the fight or flight response is initiated, and the adrenal gland injects adrenaline and noradrenaline into the circulation.

This system is part of the autonomic nervous system (the other part is the parasympathetic system) and is referred to as the sympathetic nervous system. It increases heart rate, blood pressure, and blood sugar production. Also, because the body is being readied for fight or flight, blood is diverted from the internal organs such as the stomach and the intestines to the large muscles of the legs (so you can run better) and the arms (obvious).

Stress During Pregnancy
As an internal organ, the uterus suffers the same fate as the gastrointestinal tract, having its normal blood supply diminished. What that means for a pregnant woman is that her baby will receive less blood and, therefore, less oxygen and nutrients at times of stress. If this state persists, the consequences can be dire.

It should be added that stimulation of the sympathetic system is accompanied by inhibition of the parasympathetic system. The latter promotes rest, sleep, and digestion. Its inhibition leads to wakefulness and malabsorption of food. As you can see, the fight or flight response is well suited for a person being chased by a lion but not so great for a pregnant mother’s unborn child. There is another aspect to the body’s reaction to a perceived threat. And that occurs by way of what is called the HPA Axis.

This system works beautifully under normal conditions. It is designed, for lack of a better term, to preserve homeostasis (equilibrium) or restore homeostasis as quickly as possible at times of stress. It is a feedback loop apparatus similar to the heating systems of most apartments or houses where a thermostat is set at a certain temperature.

When the temperature in the room falls below the set temperature, the thermostat will signal to the furnace, and the furnace will heat up. After a while, the house heats up sufficiently for the thermostat to tell the furnace to shut down. Everything stops until the room cools, and then the whole process starts again.

Similarly, with the body. If a pregnant woman runs to catch a streetcar, she will experience stress, but her system will quickly return to normal after she reaches the streetcar and sits down. No harm was done.

On the other hand, if this pregnant woman experiences acute stress such as the death of a loved one or loss of a job, or is a single mother worried about how she will support the child she is carrying, her amygdala, in response to these ruminations will override signals from the hippocampus (“Hey! Stop that! There is enough cortisone in the blood already!”), and stoke the fires in the adrenals, so they keep making more cortisone, adrenaline, and noradrenaline. In either case, her body is flooded with stress hormones.

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Thus, we have two possibilities: Short-lived major flooding of the mother’s and consequently her baby’s body with stress hormones or a higher-than-normal concentration of stress hormones over a protracted period. In either case, high levels of stress hormones are detrimental to the health of the mother and her unborn child.

Stress and the Developing Brain
Research has shown that abnormally high and prolonged cortisone concentrations have many harmful effects on the developing baby. In this discussion, we explore how they affect the construction of their brain.

The brain develops from the early embryo's outward-most layer, the ectoderm. The neural cells travel from the neural tube to form the six layers of the cerebral cortex. Each layer has its distinct pattern of organization and connections.

Each cell is genetically programmed to journey to a particular location in the brain. This means that under normal conditions, a neuron which, for illustration purposes, we shall call A ends up at point X and there connects with neuron B.

Great. But what if there are large concentrations of cortisone, nicotine, or other neurotoxic substance in the brain?

High cortisol concentrations in the brain will lead to cell migrations to the wrong destinations, resulting in abnormal neural circuits. If this state is prolonged (chronic stress), a large concentration of stress hormones will create massive destruction of neurons, synapses, and dendrites (each neuron receives messages from other neurons by way of up to 15,000 fine hair-like branches called dendrites).

When this process occurs in the hypothalamic and reticular activating systems, it will interfere with the child’s internal states, such as sleep and digestion. When widespread cell destruction happens in the amygdala and hippocampus, it will interfere with information entering the brain freely.

Excessive and sustained stress also leads to a marked decrease of neurons in the prefrontal cortex resulting in an increased dominance of lower brain centers over higher centers. Stress also decreases the production of oxytocin, the so-called love hormone, and increases the production of vasopressin, a hormone that supports aggressive behaviour.

The sustained secretion and circulation of glucocorticoids such as cortisol
eventually leads to a depletion of dopamine, which decreases activity in the brain's pleasure pathways; reduction of norepinephrine, resulting in a lack of motivation and alertness; and a lowering of serotonin, reducing feelings of happiness and well-being.

Due to a confluence of all these factors, this child will have a very strong propensity to develop a personality disorder.

Summary
Unfortunately, stress during pregnancy may handicap a child from before they are even born. For this reason, assuring a stress-free pregnancy for all women should be a priority of all government public health programs.