New research sheds light on why older mothers more likely to face birth complications

13 January 2017

Pregnant women over 35 years old are more likely to have complications at birth due to delayed and longer labour stages, suggests new research published in The Journal of Physiology.  

It is well known that older mothers are more likely to experience complicated births, and this new research identifies physiological changes in the body that could explain this. Using mouse models, researchers from King’s College London have discovered that maternal age influences the structure of the uterus. Specifically, they examined how the muscle of the uterus contracts, the way it responds to oxytocin (an important drug to speed up labour), and the number of mitochondria (energy supplier for cells) available to provide energy for uterus muscle contraction. They also found altered hormonal signals which underpinned the delayed onset of labour.

The average age for women to have their first child is increasing, with more women giving birth to their first child over 35 years of age. This has been paralleled by an increase in pregnancy complications such as induction for women who have passed their due date, failure to progress in labour, and bleeding after delivery. Older women are also more at risk of requiring a caesarean section or instrumented delivery (e.g., with forceps), suggesting there may be issues with the way their uterus can contract during labour.

The research team developed and used a pregnant mouse model of maternal aging. Pregnant mice at different ages were used to mimic the human situation. The average mouse has a peak fertile period between 3 – 5 months, so mice at 8 months were used to represent an older mother. They analysed the functions and physiological changes in the cervix and uterine muscles from these pregnant mice. In older mice, muscle contraction properties in the uterus were impaired, less sensitive to oxytocin and had reduced numbers of mitochondria indicating that the uterus muscles are less able to contract. Signalling of the pregnancy-related hormone progesterone was also altered and this triggered a delay in labour.

Dr. Rachel M. Tribe, Reader in Women's Health at King’s College London and lead investigator of the study explained: “Our research highlights that there are key physiological and cellular changes associated with a mother’s age that result in labour dysfunction. Timing of delivery and progress of labour is directly related to maternal age and this can cause complications during birth.”

Dr Rima Patel, Research Associate at the Division of Women's Health, King’s College London and fellow researcher added: “Our study uses a mouse model so further research involving measuring hormones and analysing uterus tissue in older pregnant women is now needed. Studies like this in maternal aging are essential to inform future clinical management strategies for older mothers to ensure more hassle-free and successful births.”

ENDS 

Notes to Editors

  1. Full paper title: Effect of reproductive ageing on pregnant mouse uterus and cervix. http://onlinelibrary.wiley.com/doi/10.1113/JP273350/full
  2. The Journal of Physiology publishes advances in physiology that increase our understanding of how our bodies function in health and disease. http://jp.physoc.org
  3. The Physiological Society brings together over 3,500 scientists from over 60 countries. The Society promotes physiology with the public and parliament alike. It supports physiologists by organizing world-class conferences and offering grants for research and also publishes the latest developments in the field in its three leading scientific journals, The Journal of Physiology, Experimental Physiology and Physiological Reports. www.physoc.org
  4. About King’s College London
    King's College London is one of the top 25 universities in the world (2016/17 QS World University Rankings) and among the oldest in England. King's has more than 27,600 students (of whom nearly 10,500 are graduate students) from some 150 countries worldwide, and some 6,800 staff.
    King's has an outstanding reputation for world-class teaching and cutting-edge research. In the 2014 Research Excellence Framework (REF) King’s was ranked 6th nationally in the ‘power’ ranking, which takes into account both the quality and quantity of research activity, and 7th for quality according to Times Higher Education rankings. Eighty-four per cent of research at King’s was deemed ‘world-leading’ or ‘internationally excellent’ (3* and 4*). The university is in the top seven UK universities for research earnings and has an overall annual income of more than £684 million.
    For further information, please visit the website: http://www.kcl.ac.uk/newsevents/About-Kings.aspx
 

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