Stress during pregnancy affects baby’s sex and brain development
Two new studies are elucidating the effects of maternal stress during pregnancy on a baby’s development. The research is finding strong correlations between levels of a mother’s stress during pregnancy and a number of birth outcomes, including fetal brain development, risk of preterm birth and even a baby’s sex.
The first study, led by scientists from King’s College London, presented the largest investigation conducted to date into the relationship between maternal stress and infant brain development. The research examined 251 prematurely born babies, comparing brain scans tracking white matter development with stress scores calculated by a questionnaire completed by the mothers.
“We found that in the mums that were more stressed during pregnancy and the period before birth, white matter was altered in the babies,” says lead researcher Alexandra Lautarescu.
Brain development in the infants was found to be altered in specific frontolimbic pathways. White matter was particularly reduced in a region called the uncinate fasciculus. It is unclear at this stage what kind of consequences result from abnormal development in the uncinate fasciculus, however, there are potential links to anxiety, Alzheimer’s, depression, and even schizophrenia.
A second newly published study, from a team of Columbia University researchers, more specifically set out to try to categorize different types of prenatal stress and identify how they can influence different birth outcomes. Combining questionnaires, diaries, and physical assessments, 187 women were followed throughout their pregnancies.
Three particular stress profiles were identified during the study: a psychological stress profile consisting of clinically significant levels of anxiety and depression, a physical stress profile incorporating high blood pressure and excessive caloric intake, and a baseline healthy profile.
One of the interesting findings in the research was that high levels of physical and psychological stress during pregnancy significantly increased the chances of a female birth. Generally, the ratio of male to female births is close to even (105:100), but those ratios notably skewed female in the presence of physical (4:9) and psychological (2:3) stresses.
“Other researchers have seen this pattern after social upheavals, such as the 9/11 terrorist attacks in New York City, after which the relative number of male births decreased,” notes study leader Catherine Monk. “This stress in women is likely of long-standing nature; studies have shown that males are more vulnerable to adverse prenatal environments, suggesting that highly stressed women may be less likely to give birth to a male due to the loss of prior male pregnancies, often without even knowing they were pregnant.”
The physical stress phenotype identified in the Columbia study also correlated with higher rates of premature birth, and reduced fetal heart rate. Higher rates of birth complications were found in the psychologically stressed group.
Both of these new studies did not particularly focus on what mechanisms could be causing these fetal effects. Catherine Monk does point out that there is a growing body of animal research suggesting stress hormones such as cortisol can directly influence fetal development.
“Stress can also affect the mother’s immune system, leading to changes that affect neurological and behavioral development in the fetus,” says Monk. “What’s clear from our study is that maternal mental health matters, not only for the mother but also for her future child.”
Both teams of scientists do agree the primary takeaway from these studies is a greater emphasis on maternal mental health during pregnancy. King’s College researcher Alexandra Lautarescu suggests the influence of maternal stress over fetal development is so strong that mental health during pregnancy should be a major part of a woman’s antenatal health plan.
“Antenatal services need to be aware that it is important to think about stress of the mums and we need to have some kind of support there for the mums who identify that they are stressed,” says Lautarescu. “If we try to help these women either during the pregnancy or in the early post-natal period with some sort of intervention this will not only help the mother, but may also prevent impaired brain development in the baby and improve their outcomes overall.”
The King’s College study was published in the journal Biological Psychiatry.
The Columbia University study was published in the journal PNAS.