UPBEAT: how does obesity affect blood loss after birth?

Professor Lucilla Poston, Dr Annette Briley, Mr Paul Seed, Ms Claire Singh

Obese women appear to be more likely to suffer from severe blood loss after birth.

Bleeding after childbirth is relatively common. If a woman loses 500ml of blood or more, this is called postpartum haemorrhage, or PPH – post meaning after, and partum meaning birth. Losing large amounts of blood can have both short and long term effects on the mother, for example increased risk of blood clotting, anaemia, and a higher risk of bleeding in future births. Recently, the number of women losing this much blood has increased, even in countries with good healthcare resources. The reasons for this are unclear and likely to be complex, but part of the puzzle may be to do with rising levels of obesity.

We have already shown that risk of blood loss increases with body mass index, or BMI, with a significant increase in very obese women. There is also evidence that heavier women suffer higher risks from losing the same amount of blood as lighter women.

We will look at women who took part in UPBEAT to explore how a mother’s BMI can affect how much blood she loses after birth. We also want to understand if changes to diet and lifestyle during pregnancy have any effect on the amount of blood lost. To do this, we plan to create statistical models that will help us understand this relationship mathematically.

This work will be valuable in helping mothers in the third stage of labour – this occurs after the baby is born, when the placenta is delivered. This is when bleeding may begin, so it is vital to give women in this stage care that takes into account the risk of blood loss. If we can use the results of this study to help carers know which women are most likely to experience heavy bleeding, they can make sure the baby is delivered in the safest way possible.

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This study takes place in a Tommy's centre and is funded by Tommy's, the National Institute for Health Research, Chief Scientist Office Scotland, and Guy's and St Thomas' Charity

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