The Frontal Cortex

Pregnancy and Stress

Over at Mind Hacks, Vaughan has a typically wonderful post on the “maternal impression” theory, which suggested that a psychological trauma inflicted on the pregnant mother would lead to profound defects in the unborn child. As Vaughan notes, this crude 19th century theory slowly faded away, as it became clear that birth defects had nothing to do with the mental state of the mother. But then, Vaughan says, the Soviet Union invaded Finland in 1939, and that all began to change.

The quickly assembled Finnish force was vastly outnumbered and ominously outgunned but, unlike their Soviet counterparts, they were quick and comfortable in the Artic conditions and made swift and deadly attacks.

In one of history’s great military victories, they defeated the Russians but suffered heavy losses. Many of the dead were young men, and many of the grieving were young pregnant women.

Nearly 40 years later, two Finnish psychiatrists decided to look at the mental health of the children who grew up without fathers. They compared children born to women who grieved during pregnancy, to those born to women who lost their husbands after the child had been born.

Their study, published in 1978, found that mothers who had lost their husbands during pregnancy were much more likely to have children who later developed schizophrenia.

Many similar studies have found that severe maternal stress during pregnancy affects the developing brain of the child, increasing the risk of cognitive or psychiatric problems later in life, possibly due to the effect of the hormonal response of the hypothalamo-pituitary-adrenal (HPA) system.

Consider this depressing finding from the lab of Elizabeth Gould . She found that if a pregnant rhesus monkey is forced to endure stressful conditions – like being startled by a blaring horn for 10 minutes a day – her children are born with reduced neurogenesis, even if they never actually experience stress once born. This pre-natal trauma, just like trauma endured in infancy, has life-long implications. The offspring of monkeys stressed during pregnancy have smaller hippocampi, suffer from elevated levels of glucocorticoids and display all the classical symptoms of anxiety. Stress, in other words, has a way of lingering on.

From the perspective of the brain, this makes a crude sort of sense. After all, if you’re mom was stressed when pregnant then you’re probably being born into a tough world. Why invest in a lavish cortex, stuffed full of new neurons? It probably makes sense to err on the side of scarcity and anxiety.


  1. #1 OneEyedMan
    January 28, 2009

    It doesn’t sound like they disentangle the paternal support effect from the mental trauma one. Men tend to support their pregnant partners, and widows don’t get that support. I don’t know how that would cause schizophrenia, but seems at least as likely as stress. Otherwise, it seems like a maladaptive strategy. Mourning during pregnancy makes your children even worse off than they have to be because their dad died.

  2. #2 Renee
    January 29, 2009


    While it’s true there could be a number of factors contributing to this difference, stress does seem the most likely, as it’s been found to cause similar problems in other animals. Stressed animals often miscarry or even ingest their young after they’re born.

  3. #3 Michael
    January 30, 2009

    Hmm…I’m not sure that I agree with the inductive leap in the closing paragraph, Jonah. From a survival perspective, it actually seems more logical that a high-stress world environment would demand an INCREASE in neuronal proliferation so that baby was born with a much-useful cognitive boost. Point being that there would need to be some alternate teleological explanation for the observed neural trimming.

  4. #4 Mary
    February 3, 2009

    I’m not sure about this either. Have you seen Janet DiPietro’s work?

  5. #5 Gen
    February 7, 2009

    I’m not going to try to say that stress on a pregnant mother will not affect her unborn child. However, the results of the Finnish study, comparing the children born without fathers to children who lost their fathers later probably had more to do with the state of the mother, than with the stressors affecting them while in the womb.

    A woman who has lost her husband before he can even meet their unborn child is going to suffer far worse from depression than a woman who loses her mate later. First of all, she goes from pregnant with a partner, to alone, to burdened with responsibility she was expecting to share. Secondly, postpartum depression is going to have a HUGE play here. For the first year postpartum, a woman is incredibly sensitive to bouts of depression after being triggered either during pregnancy, or shortly after the birth of her child. Depending on the severity of her depression, this would be a more likely explanation for the schizophrenia the children suffered from.

    The results of the rhesus monkey study are very interesting, however. I wonder what difference the offspring would have had at 1-2 years compared to those of mothers who were not exposed to stressors during pregnancy, but immediately after birth, instead? I wouldn’t want to advocate that study, though. Not nice for those poor babes.

  6. #6 Dentist Vaughan
    July 26, 2009

    Severe stress during pregancy can have significant effects on the baby.

  7. #7 Dental Vaughan
    July 26, 2009

    This is a very interesting study of rhesus monkeys that shows the impact of stress can have on a baby during pregancy.

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