Description of the condition
Overweight and obesity (body mass index (BMI) ≥ 25.0 to 29.9 kg/m2 and BMI ≥ 30 kg/m2 respectively (Who 2013)) are increasingly common among women of reproductive age (Callaway 2006; Vahration 2009). There are many known associations between overweight and obesity and adverse outcomes for both the woman and her infant during pregnancy, birth and the postnatal period.
Overweight and obesity are known to be associated with many adverse general health conditions such as hypertension (Kurukulasuriya 2011), diabetes (Reaven 2011) and PCOS (polycystic ovary syndrome) (Gambineri 2002). PCOS is a common cause of decreased fertility (also known as infertility/subfertility, or failure to achieve pregnancy within a specific timeframe) in women of reproductive ages (Hull 1987) and is associated with several late pregnancy complications (Bjercke 2002). Whilst overweight and obesity is associated with reduced fertility, the specific preconception management of women with known subfertility will not be discussed in this review as it is discussed in another Cochrane review (Anderson 2010).
During pregnancy overweight or obese women are at increased risk of experiencing a miscarriage (Frederick 2013), developing impaired glucose tolerance (decreased ability to control blood glucose levels) (Frederick 2013), sleep apnea (a sleep disorder involving pauses in breathing) (Frederick 2013), pre-eclampsia (pregnancy-related hypertension), chorioamnionitis (infection of the amniotic fluid surrounding the infant or of the membranes) (Raatikainen 2006) and preterm birth (Catalano 2006; Galtier 2008). There are additional risks of complications during labour and birth, including the need for induction of labour or caesarean birth (Catalano 2006), and also the risk of postpartum haemorrhage. Throughout the pregnancy and after the birth, overweight or obese women are also at higher risk of venous thromboembolism (a blood clot in the veins that can then break off and spread to other parts of the body) (Gray 2012).
Infants born to women who are overweight or obese are at increased risk of congenital abnormalities such as neural tube defects (a defect in the formation of the brain and/or spinal cord), structural heart defects and gastrointestinal malformations (Waller 2007). The infant is also more likely to have high birthweight (macrosomia) (Catalano 2006), which can result in increased risk of birth trauma and maternal complications (Oral 2001). Macrosomia is also recognised as a risk factor for subsequent child and adulthood obesity and its consequences (Birbilis 2012).
Description of the intervention
Preconception care is a collection of health interventions designed to best prepare and improve the woman’s physical and emotional health to increase the likelihood of a successful pregnancy and healthy infant (Whitworth 2009). It has many components and can be implemented in many ways depending on the resources available and the individual needs of the woman.
Preconception care for the general population may include advice about alcohol intake and smoking, as well as exercise, nutritional supplementation and immunisations. Less attention however, has been paid to the needs of specific subgroups of women, including women who are overweight and obese, who may benefit from specific and targeted interventions. This may include diet and lifestyle advice, active management of co-morbid medical conditions or bariatric surgery.
How the intervention might work
Women who are overweight and obese may benefit from a structured approach to preconception counselling, aiming to reduce the risks of the specific overweight and obesity complications outlined above. This approach may involve a preconception assessment of the woman's health, which could be followed by a directed and individualised plan to optimise the woman's health. This approach may include the following.
Education is an important part of preconception counselling. Informing women about the risks associated with overweight and obesity during pregnancy may allow them to make informed decisions about their pregnancy plans and timing of conception.
Preconception screening for health conditions associated with obesity
Obesity prior to pregnancy is associated with many conditions including hypertension (high blood pressure) (Kurukulasuriya 2011), impaired glucose tolerance and diabetes (Reaven 2011) and sleep apnea (Mehra 2008). Many of these conditions can be exacerbated by pregnancy. By screening for these conditions prior to conception there is the opportunity to optimise the woman's health by treating these co-morbid conditions prior to conception. For example, for some women, it might be advised to await stabilisation of blood pressure or some degree of weight loss prior to conceiving.
Management of sleep apnea
Sleep apnea during pregnancy has been associated with an increased risk of developing hypertensive disease of pregnancy and gestational diabetes (Priscilla 2013). Intensive lifestyle interventions have been shown, in the general population, to reduce apnea-associated complications and improve rates of remission (Kuna 2013). The effect of preconception interventions for sleep apnea and the outcomes for subsequent pregnancies has not been established.
Folic acid supplementation is well established as an important component of preconception care in the general population, reducing the incidence of neural tube defects. Women who are overweight and obese are reported to have lower serum folate levels (Tinker 2012), although there is no evidence to suggest that higher folate supplementation doses are beneficial. Women who are overweight or obese are reported to be less likely to take supplements during pregnancy, when compared with the general population (Case 2007).
Regular physical activity is recommended for all individuals as part of a healthy lifestyle. There are many benefits of regular physical activity including improved cardiovascular health (Metkus 2010) and improved bone density (Howe 2011). Moderate physical exercise has been shown to be safe (Larsson 2005) and has many benefits before and during pregnancy. Women who engage in regular physical activity in the preconception period are more likely to continue this during pregnancy.
General improvement of nutrition and health
Assessment of the overall nutrition of the overweight or obese women is important as it provides the building blocks for the infant. While under-nutrition is well recognised as being problematic for the pregnancy and future of the infant, over-nutrition also has implications. Infants born to women who are overweight or obese are at greater risk of having a high birthweight, which predisposes to future obesity and metabolic syndrome (Desai 2013). Not only is weight itself important but also the quality of the diet.
Many other factors affect body weight including genetics, psychological state, caloric intake and energy output. Previous Cochrane reviews have demonstrated that weight reduction is achievable in individuals who are overweight or obese with the use of low glycaemic index diets and psychological interventions, especially when these interventions are combined with exercise (Shaw 2009; Thomas 2009). Weight reduction as part of a pre-pregnancy plan may assist in lowering BMI and potentially decreasing pregnancy risk. For particular groups there may be an indication for surgical intervention to assist in weight management, and this includes gastric bypass surgery and gastric balloon insertion.
Bariatric surgery, regardless of whether restrictive (reducing the volume of food that can be consumed) or malabsorptive (reducing the area in the gastrointestinal system available to absorb nutrients), has been shown to have positive effects on many of the complications of obesity, including, diabetes, sleep apnea, dyslipidaemia and hypertension in the general population (Noria 2013). Some studies have shown improved pregnancy outcomes in obese women who have undergone bariatric surgery particularly with regards to reducing the burden of hypertensive disease of pregnancy (Bennett 2010) and diabetes (Weintraub 2008). Unfortunately, some studies have also shown increased risk of nutritional deficiencies following bariatric surgery (Bebber 2011). Surgical interventions for weight control may be indicated in some groups of women who may be at higher risk of hypertensive complications who are resistant to other interventions.
Other Cochrane reviews in this area
There are Cochrane reviews already in place that address issues in this general area. We have listed them here and described differences between the existing reviews and our planned review.
Some address care specifically before during or after pregnancy.
The review by Amorim Adegboye et al (Diet or exercise, or both, for weight reduction in women after childbirth (Amorim Adegboye 2013)) includes only breastfeeding women in the postpartum period and only includes outcomes for the mother and current child, not related to pregnancy.
The review by Furber et al (Antenatal interventions for reducing weight in obese women for improving pregnancy outcome (Furber 2013)) looks at weight control in the antenatal period. Our currently planned review is assessing preconception interventions.
A number of reviews in particular address different aspects of preconception care.
A review by Tieu et al in 2010 entitled Preconception care for diabetic women for improving maternal and infant health (Tieu 2010) includes women with pre-existing diabetes, and this group has been specifically excluded from this review.
The review by Whitworth and colleagues (Routine pre-pregnancy health promotion for improving pregnancy outcomes (Whitworth 2009)) excludes trials where interventions are aimed specifically at women with established medical, obstetric or genetic risks or already receiving treatment as part of programmes for high-risk groups and examines routine health promotion for all women.
In contrast, the review by Anderson and colleagues (Preconception lifestyle advice for people with subfertility (Anderson 2010)) is specific to those women seeking fertility treatment and this group has been excluded from this review.
The Tieu review (Interconception care for women with a history of gestational diabetes for improving maternal and infant outcomes (Tieu 2013)) only included women with a history of gestational diabetes. Our review will be looking at women with a larger range of preconception conditions, and specifically those with a BMI in the overweight or obese range.
Why it is important to do this review
Overweight and obesity are increasingly common among women of reproductive age and are associated with adverse outcomes for women and their infants. There is currently no evidence to indicate whether directed preconception health programs are of benefit, and if so, what they should include. It is important to determine which interventions, if any, are of benefit to women who are overweight or obese and how they should be implemented to improve pregnancy outcomes.