Maternal mortality constant in UK, Reasons : Maternal age, Obesity and C-section

New research from Scotland published in Anaesthesia (a journal of the Association of Anaesthetists) shows the increased risk of severe maternal sickness/complications (morbidity) is associated with a range of risk factors including increasing maternal age and levels of obesity, and also previous Caesarean section.

Even though maternal mortality is no longer reducing (although the UK rate is low by international standards), nor is it going up and the authors believe a possible explanation for this is that UK maternity services are continually adapting to meet the needs of this increasingly complex pregnant population.

In this study, the authors analysed 17 diagnoses 2 and 9 interventions 3 (including critical care admission) as a composite measure of severe maternal morbidity for pregnancies recorded over 14 years in Scotland. Any woman presenting with any of these conditions or needing any of these interventions was considered seriously ill. There were 762,918 pregnancies, of which 7947 (10 in 1000 pregnancies) recorded 9345 severe maternal morbidity events, with 2802 episodes of puerperal (post-natal) sepsis being the most common (30%). Severe maternal morbidity incidence almost doubled from 9 in 1000 pregnancies in 2012 to 17 in 1000 pregnancies in 2018, due in part to puerperal sepsis recording.

The risk of severe maternal morbidity was higher for older women, with those aged 40 years and over 44% more likely and those 35-39 years 22% more likely that those aged 25-29 years to experience it. Women with severe obesity (BMI of 40 kg/m2 or higher) were 32% more likely to experience severe maternal morbidity than those women in the normal weight range (BMI 18.5-24.9), while women in the less severely obese range (BMI 30-40) were 13% more likely than women of normal weight to experience it.

Women having a multiple pregnancy were 2.4 times more likely than women carrying a single baby to have severe maternal morbidity, and those with three or more pre-existing health problems were 4 times more likely to have it than women with no health problems. Women who had required a previous Caesarean delivery were 52% more likely to have severe maternal morbidity than those who had not.

The authors conclude that the increasing prevalence of these factors in UK mothers might stall historical reductions in maternal mortality and will increase the need for healthcare during pregnancy and childbirth." They explain that one quarter (26%) of pregnant women had obesity (BMI>30) at the time of antenatal booking in 2021, while over half of pregnant women in Scotland had overweight or obesity (BMI >25) at the time of booking in 2021. The proportion of pregnant women with obesity has increased from 1 in 5 (20%) in 2011 to 1 in 4 (26%) in 2021.5.

Reference:"Increasing maternal age, obesity and Caesarean section rates could be reasons why maternal mortality is no longer falling in the UK"; AAGBI, Anaesthesia.