Obstetrics Gynecology – MD, MSC, MMSC, Phd – Fertility Specialist

A mother’s stress level during pregnancy may affect the baby’s sex, study suggests

A study published recently suggests prenatal stress in pregnant women may affect the sex of the baby and be associated with some forms of birth complications.

Researchers at Columbia University and NewYork-Presbyterian Hospital found that stressed mothers are less likely to give birth to a male child.

The findings, which were published in the National Academy of Sciences official peer-reviewed journal PNAS, were based on data gathered from 187 pregnant women divided into three groups: healthy women (66.8% of the study), psychologically stressed women who were found to have depression and anxiety (17.1%) and physically stressed women found to have higher blood pressure and higher caloric intake (16%).

Physically stressed mothers also were more likely to have premature births and decreased fetal heart rate and movement, which researchers suggest may affect central nervous system development. All of the women had healthy pregnancies.

“The womb is an influential first home, as important as the one a child is raised in, if not more so,” said lead author Catherine E. Monk, professor of medical psychology at Columbia University, in a statement.

Pregnancy experts commonly accept that prenatal stress has an affect on a mother’s pregnancy, but the “exact mechanism” of how stress affects pregnant women’s birth outcomes is unclear — a limitation pointed out by the study.

The reason for male fetuses not surviving under times of maternal stress are unclear and require further research, but “increased adaptability” has been seen in female babies.

However, the correlation between stress and a decrease in male births is not unprecedented.

“Significant stressors such as President Kennedy’s (assassination) and the 9/11 terrorist attacks, are associated with changes in the ratio of males to females born such that fewer males were born”.

A 2006 study of 700,000 births in New York City found that the likelihood of a male brith decreased to its lowest level in the months following 9/11.

Although pregnant women are typically more likely to have male babies than female babies at a ratio of 100 girls to 105 boys, which is known as the sex ratio, the study found that women who are psychologically stressed had two male births for every three female births.

The results were more drastic for pregnant women who showed signs of physical stress: for every four male births, womenhad nine female births.

It is unclear how stress is transmitted to a fetus, that animal studies show that stress hormones are elevated during times of stress.

“Stress can also affect the mother’s immune system, leading to changes that affect neurological and behavioural development in the fetus”. 

A crucial factor into reducing stress in pregnant women, the study suggests, is maintaining a strong social support system.

“Pregnancy is an ideal time for reflecting on what kind of social support one is experiencing and whether some is missing, and identifying steps to make some changes”. There are different types of support mothers can receive: emotional support and “actionable” support, such as running errands.