Can a frightening experience during pregnancy affect the development of an unborn child’s brain? Yes.
“I had a call not long ago, before Halloween, from a pregnant woman asking if it would be OK to go to a haunted house,” said Dr. Jonathon Schaffir an obstetrician/gynecologist at Ohio State University in an interview about his research in 2007. “I told her it was fine.”
The belief that a frightening experience during pregnancy can harm a woman’s unborn baby is one of the oldest of old wives’ tales. Genetic factors and prenatal exposure to alcohol, drugs, and other toxins are the primary causes of birth defects and miscarriages, but often there is a grain of truth in long-held superstations. Epidemiological studies since 2007 reveal a strong link between severe psychological stress during pregnancy and detrimental effects on the fetus. This should not be too surprising, considering the powerful and wide-spread actions of stress hormones on the body. Chronic stress is damaging for anyone at any age, including during fetal development. Interestingly, the effects of prenatal psychological stress are especially damaging for male fetuses.
Autism, for example has been linked to severe psychological stress during fetal development. Using data from the National Weather Service on hurricanes and severe storms from 1980 to 1995 in Louisiana, together with records on the incidence of autism in children born in Louisiana during these periods, a team of researchers led by psychologist Dennis Kinney at Harvard Medical School found a strong association between the severity of hurricanes and the prevalence of children with autism born to women who were pregnant during these storms. Overall, the study published in 2008 found that the prevalence of autism disorder was about 5 children per 10,000 births, but the rate more than doubled for children born to women who had experienced the most severe hurricanes, and it jumped to 13 children with autism per 10,000 births in women who experienced the most severe storms.
The data also showed that the timing of the tragic storm with respect to the age of the fetus during the hurricane disaster was particularly important. In women who endured the most severe storms during the most sensitive periods of their pregnancy near the middle and end of gestation (between 5-6 months and 9-10 months), the rate of autism disorder shot up to 26 per 10,000 births. In part this is thought to be a consequence of the different neurodevelopmental events taking place at mid and late gestation, but also the barrier separating the fetus from hormone fluctuations in the mother’s body becomes less effective during this period. Another study found significant increased risk of fetal distress after Hurricane Andrew, and another investigation revealed that the level of prenatal maternal stress during the crippling 1998 Quebec Ice storm predicted autistic traits in children 6 ½ years later.
Other factors could contribute to the epidemiological association between autism and hurricanes. For example, a possible confounding variable might be that women who are unable to evacuate from the path of a severe storm are more likely to be in a socioeconomic class that has less resources for prenatal medical care, and have increased exposures to other environmental risk factors such as pollution. However, associations between other types of psychologically traumatic events tend to support the conclusion that severe psychological stress during pregnancy can negatively impacting fetal development. Even very stressful life events, such as losing a job or the death of a husband during pregnancy can increase the rate of autism according to a 2005 study by Beversdoff et al.
A new study published in 2016 highlights the importance of gene/environment interaction between prenatal stress and autism. This research found that children born to women with a particular genetic variant of a transporter for the neurotransmitter serotonin are at high risk for autism when their mothers were exposed to stress during their pregnancy. The serotonin neurotransmitter system is critical in many mood and psychiatric disorders as well.
In addition to autism, several other neurological and psychiatric conditions are associated with maternal stress. For example, research by Jana Veliskova and Libor Velisek at the New York College of Medicine shows that prenatal exposure to synthetic stress hormones given to mother rats results in susceptibility to postnatal seizures in their offspring, which in humans is a disorder called infantile epilepsy. Here also, males are especially vulnerable. While hormonal effects may be partly responsible for the increased male vulnerability, Dr. Veliskova says that the fundamental genetic difference between males and females is also a critical factor. Males have an X and Y chromosome whereas females have two X chromosomes, so if there is some genetic abnormality in one of the X chromosomes, the second X chromosome can take over in females, but males have no back-up.
The important lesson from these studies is that Dr. Schaffir’s reassurance to his patient that she can enjoy the thrill of a haunted house during Halloween without fear of harming her unborn child is well founded–Halloween frights are all in good fun. But real horrors that cause chronic stress at critical times during pregnancy can have detrimental effects on development of a fetus. Knowing this, supportive actions can be taken to prevent the potential risk.