A new study by Spanish scientists show that women suffering from stress before they become pregnant and during conception are almost twice as likely to give birth to a girl than a boy.
The research was conducted by Spanish researchers at the Mind, Brain and Behaviour Investigation Centre (Centro de Investigacion Mente, Cerebro y Comportamiento; CIMCYC), the Department of Pharmacology at the Pharmacy Faculty and the Psychology Faculty, all three at Granada University in Andalucia.
The researchers analysed cortisol levels in pregnant women’s hair. Cortisol is a hormone that is released as a result of stress.
Professor Maria Isabel Peralta Ramirez, 49, told Metropolitan Press in an exclusive interview that the 108 women who were part of the study had a sample of their hair taken so they could asses their cortisol levels.
The psychologist said: “Hair accumulates the level of cortisol in that organism, and as hair grows one centimetre per month, if you take three centimetres, you have the cortisol levels belonging to before conception, during conception and for the first weeks of the pregnancy”, as the women had the sample taken between the 7th and 8th week of their pregnancies.
The women were monitored during their pregnancies and births and according to Professor Peralta Ramirez, “mums who had given birth to girls had higher – even double – the levels of cortisol than the ones having boys.”
Previous research had reported that women facing extraordinarily stressful events had more girls, as was noted after President Kennedy’s assassination or after the terror attacks on 11th September 2011, she explained. But this research has gone deeper into the mechanisms that cause this.
Furthermore, instead of incorporating similar events into their study, the scientists decided to focus on common, daily stress.
Professor Peralta Ramirez explained: “There are three different types of stressful situation. The extraordinary ones, which are shocking events happening in our lives, like a car crash, the death of a loved one, or a traumatic events. Then there is the quotidian stress, which are smaller things, like work stress, traffic jams, not being able to pay bills at the end of the month, among other things.
“The last type of stress is called kept chronic stress, which is similar to the extraordinarily stressful situations but it is kept for longer, like the ones suffered by doctors working in the emergency departments dealing with people who have the coronavirus, for example.”
Professor Peralta Ramirez said that the bodies of women suffering from quotidian – daily – stress, when they are pregnant, reduce their estrogen levels, which causes a hostile cervical mucus. Professor Peralta Ramirez explained that “cervical mucus is the discharge that allows the sperm to go to the ovule, and this mucus becomes acidic, so it becomes hostile and the sperm cannot arrive to the ovule properly.”
According to the professor, sperm with the X chromosome, which creates a female embryo, are more resistant to hostile cervical mucus caused by the stress effect, but sperm with the Y chromosome, which are destined to create male embryos, are faster but “weaker and more vulnerable”.
Professor Peralta Ramirez also said that when women suffer from extraordinary stressful events, such as terror attacks or even when employees at their company are fired en masse, there is an increase in miscarriages that affects male foetuses more than female ones. She added: “It is as if nature, in these moments of adversity, is guaranteeing the survival of the species, because men can fertilise a lot of women, but if we are in a war period, nature needs more women.”
This hostile environment caused by the cervical mucus could be triggered by stress resulting from difficulties in becoming pregnant and therefore, the doctor suggested that “it would be interesting to assess psychological stress in pregnant women just before conception or after the implantation of the embryo, because if the fertilisation process is done properly but the woman is very affected, it will always have hormonal consequences.”
The hormonal imbalance caused by stress cannot be cured with medicine, Professor Peralta Ramirez said, as there is a “waterfall of hormones that affect fertilisation”.
The team’s research has also confirmed that women with high levels of stress tend to have more psychopathological symptoms, such as depression and anxiety, and Professor Peralta Ramirez claimed that “they are more vulnerable to developing postpartum depression, and it is more likely that the birth will end up being a caesarean or a manipulated birth, which is not a natural birth.”
Stress levels during the last three months of pregnancy could also lead to other consequences, such as having problems making milk to breastfeed the newborn.
The coronavirus situation is making the already stressful situation of being pregnant worse. According to Professor Peralta Ramirez, “midwives are not listening to the women anymore due to the pandemic and therefore they do not have psychological support during the pregnancy.”
She added: “The health care system in Spain does not have psychological support as a primary focus.” So the women have to deal with the stress by themselves.
In order to deal with this situation, the doctor recommended finding psychological support and engaging in calming activities such as yoga or meditation, whatever the woman feels more comfortable with, as everyone’s needs are different.
Stress can affect the baby as well as the mother. It can affect the baby’s neurological development process, causing some delays to it, according to the expert.
The team of scientists are also studying whether there more girls than boys are being born during the coronavirus pandemic.