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Increased risks in pregnancy for obese mothers and their babies, says study

A new review carried out by Trinity College Dublin and two other universities highlights that women with obesity should lose weight before they become pregnant, to avoid complications

Trinity College Dublin

Women with obesity have a range of increased health risks in pregnancy, both for them and their babies, compared with those in the healthy weight category, according to a new systematic review of research by academics at the School of Nursing and Midwifery, Trinity College Dublin, the University of Gothenberg, and City University London.

The paper, which was published today in the international peer-reviewed journal Obesity Reviews, recommends women with obesity should lose weight before they become pregnant, and also highlights the current lack of support available to these women.

Global rates of maternal obesity have reached epidemic proportions according to the researchers, with prevalence of maternal obesity in women aged 20-39 years in the US at 31.9% while the European average is 30-37%. The prevalence of pregnant women with obesity in Ireland is estimated at 20-25% at present.

Maternal obesity - defined as having a BMI of 30 kg/m2 or over when starting pregnancy, compared to the healthy weight category of between 18.5 and 24.9 kg/m2 - is linked with a range of adverse outcomes for mothers and babies during pregnancy, the birth and post-natally. Problems can include gestational diabetes, high blood-pressure, pre-eclampsia, depression, higher levels of instrumental and caesarean birth, and surgical site infection, all of which are more likely to occur in pregnant women with obesity compared to women of healthy weight.

Maternal obesity is also linked to greater risk of pre-term birth, large-for-gestational-age babies, fetal defects, congenital anomalies, and perinatal death. Furthermore, breastfeeding initiation rates are lower and there is greater risk of early breastfeeding cessation in women with obesity compared with healthy weight women. The researchers also found that maternal obesity is the most significant factor leading to obesity in their children and, coupled with excessive weight gain in pregnancy, also results in long-term obesity for women.

Professor Cecily Begley, author on the study and Chair of Nursing and Midwifery in the School of Nursing and Midwifery, Trinity, said: "Up to 1 in 5 pregnant women in Ireland suffer from obesity, a serious health problem that is not currently being adequately addressed and that can have significant implications for both them and their babies. However, it is important not to stigmatise women because of their weight. We need to provide pre-conceptual health education, through national subsidised programmes, to support and encourage women with a high BMI to lose weight before they conceive. The benefits for them and their babies can be significant."

To get a comprehensive insight into all risks related to obesity in pregnant women, the researchers produced a systematic overview of 22 systematic reviews, which looked at a total of 573 research studies comparing outcomes between pregnant women with obesity and those of healthy weight. This has resulted in an exhaustive and extensive review of the true risks associated with maternal obesity in terms of mother and baby outcomes, including physical and mental health.

The study has been welcomed by Professor Michael Turner, Clinical Lead for the National Clinical Programme in Obstetrics and Gynaecology in Ireland, who has a keen interest in this area. "Our own research in Ireland has shown similar results" he said. "The potential complications of obesity in pregnancy can lead to longer duration of hospital stay and greater costs. Given the high proportion of pregnant women with obesity, it is crucial to invest in weight loss support for these women, to reduce the risks for mothers and babies."


One strand of Trinity College Dublin's MAMMI study (Maternal health And Maternal Morbidity in Ireland), funded by the Health Research Board, is examining morbidities linked with obesity in pregnancy, with a view to developing new methods of support for women. More information on the MAMMI study is available from

The paper is available to view online at the link below.

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