News briefs

Female hormones associated with higher risk of dementia

Life events that influence levels of the female hormone oestrogen may be linked to a woman’s risk of developing dementia in later life, according to research from the George Institute for Global Health, published in PLOS Medicine. Oestradiol is the most predominant form of oestrogen during reproductive life and oestriol is the primary oestrogen during pregnancy. Use of hormones that originate from outside the body, such as oral contraceptives during reproductive years, and hormone replacement therapy in later life can also influence oestrogen levels. The researchers analysed data on 273240 women without dementia who were registered with the UK Biobank database. After adjusting for other factors that could have influenced the results, they found the following were associated with an increased risk of dementia: early and late first occurrence of menstruation; younger age at first birth; and hysterectomy – specifically hysterectomy without surgical removal of one or both ovaries, or if the hysterectomy took place after ovary removal. Conversely, the factors associated with a decreased risk were ever having been pregnant, ever having had an abortion, longer reproductive lifespan, and later menopause. The authors proposed that risk variation in women may not be associated with childbearing because a similar pattern was observed between number of children fathered and dementia risk among a similar number of men in the same study. They also found the higher dementia risk linked to early (natural and artificial) menopause was more pronounced in women of lower socio‐economic status.

https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1003955

Emergency caesarean delivery causes inflammatory response

Labour and natural childbirth cause stress on a mother’s body but an emergency caesarean delivery is associated with even more inflammatory gene expression in the placenta, according to research from Flinders University, published in Frontiers in Immunology. The researchers investigated differences in placenta inflammation markers after delivery of both male and female babies involved in 20 emergency caesarean procedures – compared with 40 placentas from vaginal deliveries and 10 placentas from elective caesarean deliveries at an Adelaide public maternity hospital between 2006 and 2018. “Labour is an inherently inflammatory process, so if you have a planned or pre‐labour caesarean section there will be less inflammasome activation than seen in an emergency caesarean section in a woman already in labour or in an unassisted vaginal birth,” said Dr Anya Arthurs, the lead author. “In births where labour is involved, there is more inflammatory gene expression in the placenta if you had an emergency caesarean section compared with a vaginal birth. This study also indicates that babies, in particular females, could be more compromised in their development and long‐term health and wellbeing after an emergency caesarean section. Interestingly, while placentas tested from baby boys have more inflammatory gene expression from a vaginal birth, baby girls born in emergency caesarean section deliveries have more inflammatory markers. One explanation for this could be our finding that placentas from baby boys tend to put out ‘alarm signals’ (known as ‘interleukin‐33’) in times of fetal distress, which we didn’t see in the placentas from baby girls. This could help to mitigate the amount of inflammation.”

https://www.frontiersin.org/articles/10.3389/fimmu.2022.807750/full