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Stress at Conception Could Make You Twice as Likely to Have a Girl

mom and baby lying on the bed

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Key Takeaways

  • A recent study found some correlation between higher levels of cortisol and female fetuses.
  • Hair samples were collected from 108 women between weeks 7 and 10 of pregnancy.
  • Other studies have also shown that fewer live births were males following large-scale stressful events.

Findings from a recent study published in the Journal of Developmental Origins of Health and Disease outline a unique way to identify stress in pregnant women: hair. Samples of hair were obtained from pregnant women and examined for levels of cortisol. It turns out the samples containing higher levels of cortisol were more often from moms carrying baby girls. 

The small study, which took samples from 108 pregnant women early in their first trimester, found that maternal hair cortisol levels were twice as high (300 mg/dl versus 150 mg/dl) in the women who were carrying a baby girl. This leads researchers to consider whether moms who are more stressed out at the time of conception are more likely to welcome a girl. 

How Does Stress Impact Fetal Sex?

It’s important to note that there are other measurements of stress that are also part of the picture when it comes to gauging stress levels in pregnant women. “We have to remember to consider the clinical measurement of a patient's stress as well, which was assessed by several different scales or questionnaires in this study,” says Kathleen Jaeger, a BJC Medical Group OB/GYN at Missouri Baptist Medical Center. “Even though a patient's cortisol level may be high or low, that does not necessarily mean that they are perceiving a different level of stress as compared to their peers.”

Kathleen Jaeger, OB/GYN

“Even though a patient's cortisol level may be high or low, that does not necessarily mean that they are perceiving a different level of stress as compared to their peers.”

— Kathleen Jaeger, OB/GYN

This study used these questionnaires in order to control for other factors that could skew the results. Using the questions answered on all three assessments, "no significant differences were found between the two groups in terms of age, marital status, educational level, employment status, type of pregnancy, number of children, number of previous abortions, pregnancy risk" or whether the pregnancy was desired or not.

This allowed researchers to zero in on the potential relationship between cortisol levels and fetal sex. "One hypothesis is that parents’ stress modifies the concentration of sex hormones through the activation of the HPA axis and has implications regarding sex allocation," the study indicates.

Other Studies Find that High Stress Means Fewer Boys

Notably, this study’s findings are consistent with those of other, similar studies. A 2010 study conducted shortly after the 9/11 terrorist attacks indicate a decline in the number of male births in the months following the event. The study indicates, “The secondary sex ratio (i.e., the odds of a male birth) reportedly declines following natural disasters, pollution events, and economic collapse.” Other studies have established a solid link between maternal stress and infertility.

Whether or not there’s an actual correlation between stress and the sex of an unborn baby, one thing’s for sure. Hair samples are a valuable method of measuring cortisol levels. 

Why is Hair a Good Indicator of Maternal Stress?

Cortisol levels can be measured not only in hair but also in saliva and blood. “But cortisol levels in those are a snapshot in time that can be affected by several different factors, including pregnancy itself,” says Jaeger. “Measuring cortisol levels in hair samples may provide a more accurate assessment of chronic stress that would not be altered by how much sleep a patient got the night before or how much they may be suffering from morning sickness that particular day.”

Managing Maternal Stress

And there’s more to that than simply whether you’ll be seeing pink or dreaming of blue during the next nine months. Maternal stress is a very real thing, and excessive amounts of it can lead to negative pregnancy outcomes like increased risk of preterm birth and postpartum depression. 

While most expectant moms won’t have their cortisol levels measured, it’s important for moms, their partners, and their doctors to keep an eye on stress levels. Lisa Westhorpe, Maternal Health Occupational Therapist MOT OTR/L, says to look for outward signs of excess stress, like the following: 

  • difficulty sleeping
  • headaches
  • digestive issues
  • increased heart rate
  • increased feelings of anxiety or depression
  • difficulty concentrating
  • difficulty with memory
  • anger
  • feeling disconnected from those around you 

Lisa Westhorpe, Maternal Health Occupational Therapist

"Moms-to-be should think about the things they used to enjoy doing and found meaningful pre-pregnancy, and see if there aspects of those activities they could still do."

— Lisa Westhorpe, Maternal Health Occupational Therapist

It's always a good idea to first consult your doctor about your stress levels during pregnancy, but Westhorpe asserts that staying active is key to managing it. "Moms-to-be should think about the things they used to enjoy doing and found meaningful pre-pregnancy, and see if there aspects of those activities they could still do."

And connection with those in similar situations - such as a moms-to-be support group or online forum - can be helpful as well, says Westhorpe. "These things can allow moms to feel that there are sources of support and connection available during the birth and postnatal period, so they don't have to feel alone and isolated."

What This Means for You

If you’re experiencing feelings and symptoms that you think could indicate high levels of stress, it’s important to discuss this with your doctor. They can help you find ways to reduce stress to ensure the best outcome for both you and your baby, no matter the sex.

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  1. Romero-Gonzalez, B., Puertas-Gonzalez, J., Gonzalez-Perez, R., Davila, M., & Peralta-Ramirez, M. (2021). Hair cortisol levels in pregnancy as a possible determinant of fetal sex: A longitudinal study. Journal of Developmental Origins of Health and Disease, 1-6. doi:10.1017/S2040174420001300