Giving birth to a boy puts more stress on a woman’s body than if she has a girl, researchers claim. They say babies create chemicals that trigger inflammation in the mother, which can harm her cells. However males make notably more of these than females. This could lead to greater long-term health risks for women who have sons, scientists believe – even contributing to the development of depression or Alzheimer’s disease. Javier Diaz-Castro, from the University of Granada in Spain, said that giving birth to a boy would not ‘feel worse in terms of pain – the pain will be the same whether it is a boy or a girl’. But he said there would be greater damage on a cellular level, as males are more “aggressive” chemically. “In terms of the response in the mother’s body, having a girl causes less inflammation,” said Dr Diaz-Castro, who co-authored the study. This is because males create more substances known as free radicals, which cause the mother’s body to respond as though it were infected. This in turn leads to more inflammation and damage. His team also found that the bodies of baby girls themselves show fewer signs of stress and inflammation after birth. The researchers followed 56 healthy, pregnant women at San Cecilio Clinic Hospital in Granada to see how their bodies responded to having children. Of these women, 27 gave birth to boys and 29 had girls. After the labour, researchers took blood samples from both the umbilical cord and the baby. These were then analysed for levels of so-called oxidative stress – when the body doesn’t have enough antioxidants to tackle the damaging free radicals. They also looked for substances produced by the body when it is inflamed. They found that baby boys were linked to greater stress response from the mother. The team has not followed women over their whole lives – however Dr Diaz-Castro thinks that as they age, women who give birth to boys may have worse health as a result. He said this was because the mother’s immune system will ultimately be affected by the sex of her child. “After having a baby girl the female body will be better adjusted,” he said. Oxidative stress is thought to be linked to numerous conditions including heart disease, Alzheimer’s and depression. The authors of the study – which was published in the journal Paediatric Research – said, “Our findings open a new, exciting field of research centred on the neonate’s sex as a risk factor for several functional alterations, with a great impact on the development of pathologies in the future.”