Page URL:

Just a little too much weight can affect IVF success

10 October 2011
Appeared in BioNews 628

Being just slightly overweight can affect the chance of having a baby through IVF, according to a study at Guy's and St Thomas' NHS Foundation Trust.

In the UK over half of women of reproductive age are either overweight or obese. Obesity has an adverse effect on natural fertility - obese women are three times more likely to be infertile and have a higher risk of pregnancy complications, including miscarriage. However, the impact of raised body mass index (BMI) on the miscarriage rate after IVF is not clear, and previous studies have been inconsistent.

Consultant Mr Tarek El-Toukhy led a study of more than 400 women undergoing IVF at the Assisted Conception Unit at Guy's and St Thomas' NHS Foundation Trust between 2006 and 2010. All the women underwent single blastocyst transfer which is associated with a higher pregnancy rate and lower miscarriage rate compared with single cleavage embryo transfer.

Overall, 27 percent (%) of the women miscarried before 23 weeks into the pregnancy. Women with a BMI higher than or equal to 25 had more than double the risk of miscarriage compared with women who had normal BMI: 38% versus 20% of the women miscarried. When the scientists subdivided the women into overweight and obese, they found these women had comparable miscarriage rates: 37% and 42% respectively.

El-Toukhy said: 'We were amazed at how large an impact being overweight – not necessarily obese – has on the success of fertility treatment. To maximise the chance of a successful pregnancy, we are now recommending that women get as close as possible to a healthy weight before starting treatment'. The authors suggest that altered hormone levels of insulin and leptin in overweight women might be to blame as these affect the endometrium (the lining of the womb) and implantation of the embryo.

The UK's National Institute of Health and Clinical Excellence states that women with a BMI over 30 who opt for IVF should be warned of potential difficulties. But El-Toukhy goes further than this and said: 'We shouldn't stop at 30, we should aim for a BMI as close as possible to the healthy range'.

'It confirms what we thought we knew', said Mr Stuart Lavery, a gynaecologist at the Imperial College NHS Trust in London. 'Now there's really good justification to employ weight loss programmes as part of fertility management'.

Dr Allan Pacey, a fertility specialist at the University of Sheffield said: 'The effect of obesity on the outcome of assisted conception has been unclear. This is an excellent study which clearly demonstrates that obesity is an important factor in the miscarriage risk after IVF. It highlights the need for women, and I would argue couples, to try and achieve a healthy weight prior to IVF'.

The study was published in the journal Human Reproduction.

A little excess weight affects IVF success
New Scientist |  4 October 2011
Being just slightly too heavy 'cuts IVF hopes'
Daily Mail |  4 October 2011
Influence of BMI on risk of miscarriage after single blastocyst transfer
Human Reproduction |  3 August 2011
11 July 2013 - by Siobhan Chan 
Obese women have a much lower chance of having a baby than those with a normal BMI when using a donated egg, according to a study of almost 10,000 women...
8 October 2012 - by Dr Lux Fatimathas 
Scratching the womb lining may increase a woman's chances of successful IVF treatment, say UK scientists...
17 September 2012 - by Sarah Pritchard 
The eggs of women undergoing IVF are significantly more likely to contain chromosomal abnormalities if the woman is severely obese than eggs belonging to women who are of a healthy weight, a recent US study suggests...
5 March 2012 - by Dr Linda Wijlaars 
Protecting embryos from a laboratory environment during IVF treatment could increase successful pregnancy rates from 35 percent to 45 percent. A novel system, trialled in a recent study, consists of a chain of fully enclosed, interlinked incubators, provides a tightly controlled and protected environment...
24 October 2011 - by Dr Rosie Morley 
Researchers at Oxford University have developed a test that may help to improve IVF success rates by checking the health of embryos. The team, led by Dr Dagan Wells, has apparently developed a test which checks embryos during IVF for abnormal numbers of chromosomes...
26 September 2011 - by Victoria Kay 
Doctors in Canada will consider a policy to withhold IVF to obese women at a national meeting of fertility experts this week....
28 February 2011 - by Ayesha Ahmad 
A survey by Pulse, a weekly magazine aimed at General Practitioners (GPs), has revealed that 31 percent of GPs report that their patients are facing restrictions in IVF treatment following the latest cost-saving measures...
28 June 2010 - by Dr Charlotte Maden 
Women using assisted reproductive technology (ART) to conceive have a higher rate of miscarriage if they are overweight, say a group of UK scientists....
21 October 2009 - by Sarah Pritchard 
Women who are overweight or obese have lower chances of successful IVF treatment, according to researchers reporting at the American Society for Reproductive Medicine (ASRM) conference in Atlanta, US, this week. The researchers, from Michigan State University in the US, found that women who were defined as clinically obese were up to 35 per cent less likely to conceive and have a live baby, and twice as likely to have a stillbirth, than their lighter cou...
4 January 2009 - by Sarah Pritchard 
The results of a study in Scotland have indicated that obese and overweight women have the same chance of successful IVF treatment as normal weight women. The research was undertaken in Aberdeen between 1997 and 2006, on 1,700 women undergoing their first cycle of IVF, and included...
to add a Comment.

By posting a comment you agree to abide by the BioNews terms and conditions

Syndicate this story - click here to enquire about using this story.