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Women who go through stress around conception time are twice as likely to conceive a girl, study finds

A study carried out by scientists from the University of Granada (UGR) has revealed that women who experience stress both before becoming pregnant and during conception are almost twice as likely to have a girl as a boy.

The findings confirm that foetuses are vulnerable to the effects of maternal stress and that such can play a key role in their development.

How was the study conducted?

1. Researchers in Spain enrolled 108 women to participate in the study.
2. These were monitored from the first weeks of pregnancy through to delivery.
3. Scientists recorded their stress levels before, during, and after conception.
4. The method they used for this was by checking the concentration of cortisol in their hair and various psychological tests.
5. Each hair measurement covered the cortisol levels for the preceding three months as per the calculation that hair grows @ a centimetre per month.
6. The first test taken was therefore a reflection of the women’s stress levels in the period prior to and including conception.
7. Subsequently, the UGR scientists recorded different variables relating to the birth and the sex of the baby.
8. María Isabel Peralta Ramírez, the main author of this work is a researcher at the UGR’s Department of Personality, Evaluation and Psychological Treatment.

She looks at this study and its results as ample scientific evidence demonstrating the impact of stress on the mother in the processes of pregnancy, birth, and even infant neurodevelopment.

Ramirez explains: “The results we found were surprising, as they showed that the women who had given birth to girls presented higher concentrations of hair cortisol in the weeks before, during, and after the point of conception than those who had boys.” In fact, these cortisol concentrations in the hair of mothers who subsequently had girls were almost double those who had boys.

Two theories to possibly explain the outcome:

The hypothalamus-pituitary-adrenal gland system is called the “stress system”. This setup controls the increase in cortisol secretion and modifies the concentrations of sex hormones at the time of conception. Not much clear at the moment but perhaps the testosterone could influence the determination of the baby’s sex (higher the levels of prenatal stress, the higher the levels of female testosterone).
The second possibility is that there is scientific evidence that sperm carrying the X chromosome (which determines that the baby will be female) perform better at passing through the cervical mucus in circumstances of adversity. So, when stress alters the mother’s hormones, these sperm are more likely to be successful in reaching the egg than sperm carrying the Y chromosome (which determines that the baby will be male).

Stress affects the unborn baby’s development:

According to a report (on a research study) published in The Guardian, stress experienced by a woman during pregnancy may affect her unborn baby as early as 17 weeks after conception, with potentially harmful effects on the brain and development,. The study is the first to show that unborn babies are exposed to their mother’s stress hormones at such an early stage in pregnancy.

The findings, published in the journal Clinical Endocrinology, come after separate research on animals showed that high levels of stress in a mother during pregnancy could affect brain function and behaviour in her offspring, and other evidence suggesting that maternal stress in humans can affect the developing child, including lowering its IQ.

Further research on the way this happens and the implications for the unborn child, both before and after birth, need to be studied separately and further, the latest study’s authors said.