According to the results of latest research study conducted at the Department of Health and Environment of the JU MC Institute of Public Health, every time a woman gives birth to a male baby, she increases her chances of health problems in the future. What is the reason for that? How should we interpret it?
Together with his team, Dr Andrzej Galbarczyk has conducted a five year long research project, examining over 500 women of postmenopausal age living in the area of Island Beskids.1 Why there? The region is simply known for its high birth rate: statistically, every participant of the study has given birth to four children.
The study began with Dr Galbarczyk asking his patients to subjectively assess their own physical health in the last twelve months. It was then juxtaposed with the number of sons and daughters they have brought to this world. It soon became obvious that every male child has significantly contributed to a decline in the mother’s health when she became older. Conversely, the number of daughters had no impact on their well-being. What are the causes of this phenomenon and what can we do with this data?
Baby’s sex vs. mother’s health
Giving birth to a large number of children has an adverse effect on the female organism. There are many studies which show that intensive reproduction (e.g. having five or six children) has a lasting impact on the mother – when they reach old age, such women may experience numerous health problems, partly because of increased oxidative stress.2 They tend to look much older than other women their age with less numerous offspring,3 and they have shorter lifespans as well (this is known due to historical data).4
Dr. Galbarczyk’s research proves that giving birth to a son makes a big difference when compared to a daughter. In most cases, males are noticeably bigger than females (this is caused by the fact that male foetus develops faster), forcing the mother’s body to provide them with more nutrition.5 What’s more, male foetuses stimulate their mothers’ bodies to produce higher calorie milk, allowing for more rapid physical development.6
Sons are also much more of a strain on their mothers’ immune system, because the Y chromosomes, present only in males, contain genes which produce protein absent in the female organism, and therefore, completely alien to it. Older women with more sons can suffer from mild chronic inflammations.7
A real threat to mothers?
Dr Galbarczyk’s study was conducted on women over 50 who have given birth to more children than the current average (together they have over 2300 children!). However, there are also other factors to consider, such as the fact that the participants of the study have lived, given birth, and raised their offspring in much harsher environment than we have now.
In malnourished populations, e.g. in Africa, every pregnancy makes a woman thinner and less physically fit. In Western countries, women receive much more support, both socially and medically. Indeed, pregnant women often gain weight as their organism prepares for increased energy expenditure. If a woman has access to plenty of nutritious food, it’s safe to assume that she will be able to have as many children as she wants (at least energy-wise). Moreover, we can assume that, statistically speaking, a modern woman living in a city and giving birth to one or two children is not exposed to the ‘reproductive costs’ related to high birth rate. Therefore, it’s reasonable to think that a healthy woman with in a stable financial situation can have many sons and not experience a decline in health.
Research conducted by the JU MC Department of Health and Environment increase our knowledge about women’s health (particularly in the old age) and what factors affect its quality. A suitable choice of treatment and preventative health care tailored to individual patients with known reproductive history (including the sex of her children) can result in a considerably more effective medical care, and even minimise the risk of diseases or disorders.
1 A. Galbarczyk, M. Klimek, I. Nenko, & G. Jasienska, Sons may be bad for maternal health at older age. New evidence for costs of reproduction in humans. The Journals of Gerontology: Series A, (2018) gly190. https://doi.org/10.1093/gerona/gly190.
2 A. Ziomkiewicz, A. Sancilio, A. Galbarczyk, M. Klimek, G. Jasienska, & R. G. Bribiescas, Evidence for the cost of reproduction in humans: High lifetime reproductive effort is associated with greater oxidative stress in post-menopausal women. PLoS ONE, 11 (2016). https://doi.org/10.1371/journal.pone.0145753.
3 U. M. Marcinkowska, A. C. Little, A. Galbarczyk, I. Nenko, M. Klimek, & G. Jasienska, Costs of reproduction are reflected in women’s faces: Post-menopausal women with fewer children are perceived as more attractive, healthier and younger than women with more children. American Journal of Physical Anthropology, 165 (2018). https://doi.org/10.1002/ajpa.23362.
4 S. Helle & V. Lummaa, A trade-off between having many sons and shorter maternal post-reproductive survival in pre-industrial Finland. Biology letters, 9 (2013) 20130034. https://doi.org/10.1098/rsbl.2013.0034.
5 R. M. Tamimi, P. Lagiou, L. A. Mucci, C.-C. Hsieh, H.-O. Adami, & D. Trichopoulos, Average energy intake among pregnant women carrying a boy compared with a girl. BMJ (Clinical research ed.), 326 (2003) 1245–6. https://doi.org/10.1136/bmj.326.7401.1245.
6 C. E. Powe, C. D. Knott, & N. Conklin-Brittain, Infant sex predicts breast milk energy content. American Journal of Human Biology, 22 (2010) 50–54. https://doi.org/10.1002/ajhb.20941.
7 S. Marttila, T. Nevalainen, L. Kananen, J. Jylhävä, M. Jylhä, A. Hervonen, J. Ilonen, & M. Hurme, Number of sons contributes to ageing-associated inflammation. Scientific reports, 5 (2015) 8631. https://doi.org/10.1038/srep08631.
Picture: Georgios Iakovidis, Maternal affection
Original text: www.nauka.uj.edu.pl