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Research report

Barriers encountered when recruiting obese pregnant women to a dietary intervention

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Maternal obesity has health implications for mother and baby but a study revealed how midwives were reluctant to raise this issue with women in their care


Bridget A Knight, PhD, MSc, RGN, RM, RN, is a research midwife, Peninsula NIHR Clinical Research Facility; Katrina Wyatt, PhD, MSc, is a senior research fellow in child health, both at Peninsula Medical School, University of Exeter.


Knight BA, Wyatt K (2010) Raising issues of obesity with pregnant women: the implications for pregnancy related obesity research. Nursing Times; 106: 31, early online publication.

Background Obesity in pregnancy is increasing. It carries significant risks for the mother and her baby, and has considerable implications for the family and the maternity services. Specific guidelines have been developed for the identification and management of the associated clinical risks, but there is little evidence of an optimum dietary intervention for these high risk mothers.

Aim This study assessed the feasibility of recruiting into a proposed dietary intervention project aimed at reducing the incidence of excessive weight gain during pregnancy for mothers with a raised body mass index (BMI) in early pregnancy.

Method Women in early pregnancy (8–10 weeks) with a BMI greater than 30kg/m2 were identified and offered the opportunity to participate in a project which delivered specific dietary advice and ongoing motivational support at the time of routine antenatal appointments throughout their pregnancy.

Results and discussion Over a four month period, 25 women out of a potential 172 were recruited into the study; a recruitment rate of 14.5%%. Midwives were crucial to the recruitment strategy, but cited personal and professional reasons for their reluctance to address directly the issue of obesity in pregnancy with pregnant women.

Conclusion Recruitment for this study and any future obesity intervention study is problematic due to the perceived sensitivity surrounding obesity in pregnancy and the subsequent discomfort that professionals feel towards raising the issue.

KeywordsMidwifery, Obesity, Pregnancy, Research

  • This article has been double-blind peer reviewed



Practice points

  • The incidence of maternal obesity is increasing.
  • Maternal obesity has health implications for both mother and baby.
  • Midwives are reluctant to address with pregnant women the issue of obesity in pregnancy.
  • Midwives require guidance and support to address this sensitive issue.




Obesity is a complex problem. Although personal responsibility plays a part, the ready availability of energy dense foods and an increasingly sedentary lifestyle is producing a society that almost perceives being overweight as normal (Foresight, 2007).

It is estimated that 57% of women in England over the age of 16 are overweight and that 24%are classified as obese; that is, have a BMI greater than or equal to 30kg/m2 (Box 1 outlines how to calculate a BMI and what BMI scores indicate). The related healthcare costs are suggested to be £4.2bn per year. If current trends continue this figure could double by the year 2050 (NHS Information Centre, 2009).

Box 1 Body mass index

Body mass index can be calculated by dividing body weight in kilograms by height in metres squared.

                                                            Weight (kg)

Body mass index =

                                                            Height (m)2


Below 18.5kg/m2Underweight
18.5–24.9kg/m2 sqIdeal weight
25–29.9kg/m2Over the ideal weight
Above 40kg/m2Very obese


This general trend of increased BMI in the female population is reflected in the proportion of obese women booking with the maternity services – the figure has more than doubled (from 9%%to 18.9%%) in the past decade (Kanagalingam, 2005). Moreover, it is now considered the most common clinical risk factor in obstetric practice (Krishnamoorthy, 2006).

The Confidential Enquiry into Maternal and Child Health (CEMACH) (2007) recently highlighted that obesity in pregnancy carries significant risks and identified that over half the women who died either directly or indirectly from pregnancy related causes were overweight or obese. Sebire (2001) stated that when compared with mothers of ideal weight, obese mothers are also at increased risk of:

  • Gestational diabetes;
  • Proteinuric pre-eclampsia;
  • Delivery by emergency caesarean section;
  • Delivering an infant with a birth weight above the 90th centile.

This has considerable implications for the mother and her family, as well as the maternity services. While services have responded to the growing problem of obesity in pregnancy by developing specific guidelines for the identification and management of the associated clinical risks, an optimum dietary intervention for these high risk mothers has not been identified.

Studies conducted on non-pregnant obese women have suggested that even a 10%%reduction in body weight may have significant health benefits (Orzano, 2004). While this would be the favoured pre-conceptual approach, given that up to half the pregnancies in England and Wales are unplanned (Rowlands, 2007), a more practical approach may be needed. We know overweight or obese women often gain more weight during their pregnancy than is recommended (Rhodes, 2003), which often results in offspring who are bigger and fatter at birth (Knight, 2005) and in early childhood (Knight, 2007).

Current guidelines (NHS, 2009) identify that pregnancy is not the time to diet and suggest that most women put on 10–12kg. Clinical experience identifies that women consider pregnancy to be a time when they do not have to worry about putting on weight. This view may Iimit the scope for a dietary intervention aimed at avoiding excessive weight gain.


Health professionals have the potential to make a positive impact on the amount of weight gained during pregnancy by providing specific dietary advice and tackling individual motivation. However, this is a complex intervention which requires thorough testing in order to provide the necessary evidence base. This pilot project was a preliminary step to assess how feasible and acceptable the development of such an intervention might be. One of the first things to determine were issues concerning recruitment; for example, how easy would it be to get women involved and would they want to stay involved?

Ethical approval for the study was obtained from the Devon and Torbay Research Ethics Committee in 2008.


This was a community based project conducted in Exeter. The local maternity unit has approximately 3,000 deliveries per year and approximately 40% of the unit’s expectant women are overweight or obese. It is one of the few units in England to offer a first trimester screening clinic (FTSC), which aims to provide women in early pregnancy (11–14 weeks’ gestation) with a one stop appointment that involves an ultrasound, routine antenatal blood tests and optional screening for Down’s syndrome. Access to this service is usually arranged in early pregnancy (8–10 weeks gestation) by a community midwife or GP.

Women have their height and weight measured routinely when booking in with the maternity services (6–8 weeks’ gestation). Weight is needed prior to booking a FTSC appointment and a BMI is calculated to identify those at risk due to a low BMI (less than 18.5kg/m2) or a high BMI (greater than 30kg/m2) who may need referral to consultant services. Women with a BMI greater than 30kg/m2, who were not diabetic and were not carrying twins, were informed of the project by their midwife and asked if they would be interested in hearing more about it. If they agreed, their contact details were passed to the project midwife.

The project midwife had a good working relationship with the local midwives and explained to them during the developmental phase that the project was not a weight loss programme; it was aimed at preventing mothers from gaining too much weight during their pregnancy. The midwives were reassured that their role was purely identifying potential recruits – that is, women with a raised BMI in early pregnancy – and that the project midwife would then be responsible for recruiting them to the study and subsequently providing routine antenatal care and the proposed dietary intervention for those who agreed to participate. Midwives were given a copy of the patient information sheet which explained the current absence of help and advice for women with a raised BMI in pregnancy and how the project aimed to examine ways to prevent overweight women from gaining too much additional weight during pregnancy in order to reduce the risk of complications for mothers and babies and hopefully help mothers to lose weight after their baby’s birth. 


Over a three month period, 127 women appeared to meet the entry criteria and were therefore potential recruits. Of these,  only two were referred by their midwife for more information, and when subsequently contacted by the project midwife, neither wanted to take part.  

Due to the lack of success of the initial recruitment strategy an alternative was developed. On attending the FTSC women are weighed again, usually by a healthcare assistant (HCA), to ensure an accurate figure is incorporated into the screening test. The project midwife approached the HCAs to ask for their assistance in raising awareness of the project. The project and eligibility criteria were discussed with them and it was explained that their role was to ask women if they would be interested in finding out more about the project. Suggestions were offered for how to introduce the project to mothers; for example, “one of our midwives is doing a project on the best advice to give to mothers who may be a bit overweight for their height. Would you be interested in hearing more about it?”

Over the next four months, 172 women appeared to meet the entry criteria for the project. Of these, 67 expressed an interest, were sent written information, and subsequently telephoned by the project midwife. This resulted in 25 women being recruited to the study. Of these, five helped assess and refine the study paperwork, while the other 20 were randomised to one of two groups: one group received routine antenatal care and the intervention, the other group received only routine antenatal care. Data from the trial arm of the project are currently being analysed for publication.


One of the areas the pilot study wanted to assess was how easy it would be to recruit pregnant women with a BMI greater than 30kg/m2 into a dietary intervention study. The preliminary results indicated that recruitment was difficult. The recruitment rate of 14.5% is much lower than the rates achieved for recent local dietary intervention studies: a study focusing on diet and weight loss in patients with type 2 diabetes achieved a recruitment rate of 28% (Daly, 2006), while another on healthy eating to reduce the risk of diabetes in overweight adults achieved a rate of 33% (Greaves, 2008).

It had been anticipated that pregnant women would have had a similar motivation to these groups in terms of addressing a health related issue, as well as the greater incentive of the health of their growing baby, however this was clearly not the case. As previously mentioned, many women feel that pregnancy is not the time to “diet” and, in fact, expect their weight to increase – they are not in the correct frame of mind to approach any dietary modification.

When the initial recruitment strategy failed, the project midwife spoke directly to a number of midwifery colleagues to try to identify what the difficulties might be. The initial reasons given by midwives were usually “too busy” or “just forgot”, both of which are understandable in the context of busy antenatal clinics. However, as conversations developed it became clear that many midwives felt uncomfortable about raising the issue or asking women if they would be interested. Some feared upsetting the women in their care by raising the issue of obesity, while others found it difficult to discuss due to personal weight issues.

The obesity rates for the general population are reflected in the NHS workforce, where the number of nurses and midwives who are overweight or obese is increasing (DH, 2009). This has the potential to affect how the effectively dietary advice is delivered and how well it is received. Early participants to the project were asked if they would have a problem being recruited to the project by a person who was overweight. Although most participants said they were unsure, several were adamant that they would have a problem with it.

Although the second recruitment strategy was more successful than the first, it was also slow and problematic. The HCAs who helped with the study had worked in the maternity services for many years and were experienced in dealing with pregnant women and their families, however, they were initially reluctant and felt awkward about raising the subject through fear of embarrassing anyone. Initially they did not all women who met the study criteria as they perceived that some would not be interested.

Selecting who to ask was often based on what the women looked like rather than a BMI calculation. However, using “looking big” as a selection criterion can be flawed because the general increase in obesity has distorted our perception of what is considered normal. The director of the Cancer Research UK Health Behaviour Research Centre recently said, “there is a wide presumption that the average weight of people around you is normal, but this isn’t true. The majority of the population is overweight” (Wardle, 2008). One study from Plymouth (Jeffery, 2004) showed that 40% of overweight mothers and 45% of overweight fathers thought that their weight was “just right”. Perhaps more worrying was that only 25% of these parents recognised that their child was overweight. However, this inability to recognise the problem is not confined to the lay public: a further study from Germany (Bramlage, 2004) identified that health professionals could only correctly classify 20–30% of overweight patients as being overweight.


This pilot project appears to have identified an important potential barrier to conducting research in this area. While it was anticipated that any research involving maternal obesity would be challenging, the difficulty was originally assumed to be in developing an intervention for obese pregnant women, rather than identifying and recruiting possible participants.

Maternity staff are crucial to these projects, yet appear uncomfortable about mentioning the subject. Midwives routinely discuss such sensitive issues as domestic violence, mental health and drug use, however this requires specific training and support. The apparent difficulty in addressing the issue of obesity in pregnancy may reflect a training need.

The highly visible nature of obesity, and the sensitivity surrounding the issue for both midwife and mother, may affect midwives’ ability to discuss the potential consequences of obesity in pregnancy in a creditable way. It may be that there is a need to help staff address feelings about their own weight before developing an intervention that can have a long term impact on reducing the complications associated with obesity in pregnancy.


This study was funded by The Burdett Trust for Nurses.

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