13.1 Obesity
EXPLANATION OF CONDITION
Obesity is considered to be one of the most significant health concerns affecting current society, where an individual’s risk of serious morbidity and/or mortality is directly related to their increasing weight through the development of disease pathways attributable to obesity, although these pathways are unclear as individuals of normal weight also develop these conditions. The trend in the rate of obesity is upward, with an estimated 50% of women of childbearing age being classed as obese by 20502. Obesity was a factor in 35% of maternal deaths3 and has a significant influence on pregnancy outcomes4.
- Defined as the excessive accumulation of fat within the fat cells as a result of discrepancy between energy intake and energy expenditure, obesity is a complex interplay between biology, hormonal, and emotional and psychosocial issues
- It is diagnosed using the body mass index (BMI) classification as recommended by NICE, which is the weight in kilograms divided by the square of the height in metres (see Appendix 13.1.1)
- Obesity is defined as a BMI ≥30, with underweight as <18.5, normal weight 18.5–24.9 and overweight 25–29.9. Obesity can be further subdivided into Class 1 (BMI 30.0–34.9), Class 2 (BMI 35.0–39.9) and Class 3 or morbid obesity (BMI ≥40)
- Of similar significance is the distribution of body fat, especially an increased waist-to-hip ratio; thought to be more valuable than weight alone and suggestive of disordered glucose tolerance
Obesity is also associated with:
- Gender – more common in women than men
- Postcode – there are more cases in the north of the country than in the south of the UK
- Lifestyle – increasing sedentary occupations, reliance on the car, fast food, etc.
- Mental wellbeing – depression may be linked with obesity
- Social class – rates of obesity increase as the social class lowers
- Ethnicity – increased obesity seen in certain ethnic groups, e.g. Afro-Caribbean
- Genetics – some obesity has an inherited component, although this accounts for only a small proportion of cases
COMPLICATIONS
There is a continuous relationship between obesity and morbidity and mortality and it is a common risk factor in many conditions, especially:
- Metabolic (e.g. type 2 diabetes)
- Circulatory (e.g. cardiovascular disease)
- Degenerative (e.g. osteoarthritis)
These conditions are usually associated with advancing age, although with increases in childhood obesity the age of presentation of many of these conditions is lowering.
Many of these diseases have a negative effect on life expectancy and there are increased morbidity rates for individuals with obesity. The amplified health and social welfare costs for society in managing obesity-related conditions is also a concern, especially due to shifting population demographics. Individuals with obesity also suffer from discrimination and stigma directly attributed to their size, which may lead to lower self-esteem and self-confidence; many individuals with obesity report an overall poorer quality of life5–7.
For women, obesity increases the risk of gynaecological complications, e.g. endometrial cancer, infertility and menorrhagia through menstrual disturbances and ovulation disorders. In the presence of sub-fertility, to increase the chances of spontaneous conception through regular menses or to increase the sensitivity of ovulation-induction techniques, women with obesity are recommended to achieve a moderate weight loss of at least 5%8.
Therefore, weight loss to achieve a normal BMI has short- and long-term health benefits.
NON-PREGNANCY TREATMENT AND CARE
The management aim is to attain a steady weight loss until the BMI is within the normal range. Slow weight loss is more sustainable in both the short- and long-term. This is achieved through education about what constitutes a healthy diet and eating patterns and lowered overall energy intakes. Moderate exercise in combination with a well-balanced, energy-restricted diet has been shown to increase weight-loss success rates by:
- Increasing overall muscle mass (which consumes more energy than fat)
- Producing a sense of wellbeing
- Depressing the appetite
- Increasing the overall metabolic rate
Studies have also shown that behavioural and cognitive therapy combined with the above can augment success rates9. Group therapy, e.g. Weight Watchers, may also improve success rates.
Some obese individuals resort to surgery. There are two main types of surgical techniques: restrictive, e.g. gastric banding, and malabsorptive, e.g. stomach stapling. Bariatric surgery increases the risk of malnutrition, anaemia and vitamin deficiencies which may negatively affect pregnancy10. There has also been renewed interest in diet pills, e.g. orlistat (a lipase inhibitor) and sibutramine (a centrally-acting appetite suppressant), although these must be prescribed and supervised closely by the medical team and are contraindicated in pregnancy11.
PRE-CONCEPTION ISSUES AND CARE
Because of the strong association with maternal mortality/morbidity and the problems outlined in this chapter, pre-conception support and advice should be available for all women with a BMI ≥30 in order that they achieve a normal BMI prior to pregnancy4. Bariatric surgery to achieve weight loss does improve a woman’s fertility if obese12. Encourage all women with obesity to take 5 mg of folic acid supplementation pre-conceptually and during the first trimester4.
- Early miscarriage
- Gestational diabetes and pregnancy hypertension/pre-eclampsia13–16
- Venous thrombo-embolism2
- Anaesthetic problems, e.g. tracheal intubation or epidural/spinal insertion2
- Neural tube defects16
- Late stillbirth3 and neonatal death17
- Fetal macrosomia18
- Fetal trauma2
- Neonatal unit admissions
- Difficulties in performing amniocentesis19
- Difficulties in achieving venous access
- Difficulties in performing an abdominal palpation20
- Difficulties in obtaining ultrasound data for fetal anomalies21 and growth
- It is important to identify those women who have co-morbidities directly attributed to their obesity, in particular GDM (offer a Gamma-GT [GTT]4) and hypertension
- The presence of related conditions will directly influence their care needs; a multidisciplinary team approach to management during pregnancy is advised2
- Women with a BMI ≥40 should have an antenatal anaesthetic referral screen4
- Encourage all women with obesity to take 10 mg of a vitamin D supplement throughout pregnancy and while breast-feeding4
- All women have their BMI calculated as part of a full risk assessment performed at booking and women found to have a BMI ≥30 should be referred to a consultant to discuss intrapartum risks and management strategies4
- Women with a BMI ≥35 should be booked in a consultant-led environment4
- All women should receive advice about healthy eating in pregnancy4,26; seek out and access any locally provided support groups focusing on obese women in pregnancy, which include specialist midwives and dieticians
- There are no evidence-based UK guidelines on recommended weight gain ranges during pregnancy and dieting in pregnancy should be avoided27
- Moderate exercise should be encouraged, unless the woman is experiencing other signs or symptoms, i.e. dyspnoea28
- Individualised advice, especially options for fetal anomaly screening, is important, taking into account the effects of weight on biochemical results
- Careful observation of the maternal and fetal status is important during pregnancy to detect complications; community monitoring for pre-eclampsia at least every 3 weeks between 24 and 32 weeks for women with a BMI ≥35 is recommended4
- Ascertain mobility; assess risks of potential intrapartum moving and handling/environmental concerns in preparation for birth4
- Continuity of care and support to foster self-esteem and self-confidence
- Increased rates of prolonged labour22
- Risks associated with macrosomia, e.g. shoulder dystocia2,13
- Increased rates of operative birth2 especially for primigravida23
- Difficulties in undertaking instrumental and operative procedures13
- Difficulty siting an epidural or spinal for labour or caesarean section
- Encourage birth in a consultant-led environment4
- Avoid induction of labour where possible and aim for a vaginal birth4
- Strongly consider thrombo-embolic prophylaxis21 and secure venous access on admission if BMI >404
- Consider the differences in labour progression in obese women before resorting to augmentation22
- Effective midwifery support in labour is important; women with a BMI ≥40 should receive continuous midwifery care in labour4
- Encourage changes in maternal position throughout labour
- Avoid dehydration in labour (risk of venous thrombo-embolism)
- Observe progress – use the partogram carefully throughout labour
- Fetal scalp electrode for difficulty with abdominal auscultation of the fetal heart
- Venous thrombo-embolism; obesity in the presence of two other persisting risk factors should prompt the need for thrombo-prophylaxis for 3–5 days2,24
- Longer post-operative recovery and increased rates of post-operative complications, e.g. infections of wound and urinary tract4
- Women who are obese during pregnancy tend to retain fat centrally on their abdomen postnatally, which may result in increased morbidity and mortality in later life25
- Lower rates of breast-feeding
- Contraceptive choices will be influenced by the presence of complications
- Multidisciplinary approach to the management of associated conditions
- Encourage women to lose excess weight to achieve a healthy BMI prior to any subsequent pregnancy4
- May need increased post-operative analgesia30
- Early mobilisation4; continue thrombo-embolic prophylaxis until fully mobile4
- Encourage and support breast-feeding to help mobilise fat stores: tailor breast-feeding advice to meet individual needs; suggest underarm positioning at the breast
- Review postpartum weight at the 6–8 week check and consider referral to the MDT for support and advice regarding weight reduction and moderate exercise27
- Consider referral for cognitive and behavioural therapy and consider providing extended midwifery postnatal care31
- The combined contraceptive pill may not be as effective in obese women
- Repeat GTT at 6 weeks postnatal if GDM diagnosed during pregnancy4,26
13.2 Phenylketonuria
EXPLANATION OF CONDITION
Phenylketonuria (PKU) is an autosomal recessively inherited inborn error of amino acid metabolism, caused by mutations in the gene for phenylalanine hydroxylase, found on chromosome 12. Phenylketonuria, as a disease, was first recognised in the 1930s, but maternal PKU syndrome as a complication was not documented until the 1950s2.
There are two main types of phenylketonuria:
Phenylalanine hydroxylase is an enzyme produced by the liver that converts the amino acid phenylalanine, which is found in dietary protein, to another amino acid called tyrosine. Amino acids are important building blocks for proteins, which are vital for growth and wellbeing. In individuals with PKU, phenylalanine and its by-products accumulate in the body and will result in neurological symptoms and irreversible damage to nerve cells within the developing brain and nervous system.
As this is a recessively inherited disorder3:
- A woman with PKU whose partner does not carry the affected gene for PKU will produce unaffected children
- the couple will always pass on the affected gene to their infants, who will be carriers
- carriers do not exhibit signs of PKU – a child would need to inherit both affected genes to inherit and express symptoms of PKU
- A woman with PKU whose partner also carries an affected gene for PKU will have a one in two chance of having an affected child
- If a woman’s partner also has PKU, all children conceived will have PKU
- Individuals who are both carriers of the PKU gene will have a one in four chance of conceiving a child with PKU
COMPLICATIONS
Complications will occur in affected individuals unless screening to detect the condition and management to control the condition is instigated. The earlier treatment begins the less affected the child will be; some limited evidence suggests that the diet should be modified within the first month of life for best results4.
A neonate will appear normal at birth, as the mother will have processed phenylalanine through her bodily systems during pregnancy. Symptoms in untreated affected infants will begin to appear from 3–4 months of age onwards. These include:
- Abnormal movements
- Developmental delay
- Decreased muscle tone
- Difficulty walking
- Microcephaly
- Learning disabilities
- Seizures
- Psychosis
- Reduction in IQ
- Skin conditions, e.g. eczema
- Pale skin
Attention deficit hyperactivity disorder (ADHD) is also associated with biological insults such as PKU; this is thought to be dose-related and associated with high levels both before birth and in the neonatal period5.
NON-PREGNANCY TREATMENT AND CARE
All mothers of newborn infants are offered screening for the condition in their baby within the first week of life1.
Treatment of affected infants consists of a low phenylalanine diet and a supplement of synthetic amino acids (protein substitutes) and vitamins, minerals and trace elements, with food exchanges. This modified diet should continue throughout childhood and some studies suggest this should continue into adulthood6. Foods that are naturally high in phenylalanine include meat, dairy produce and nuts, while foods that are low in phenylalanine are generally fruit and vegetables and are considered to be phenylalanine-free foods7. A traffic-light approach to foods is taken.
The diet is restrictive and studies have shown that it is difficult to adhere to8; social support has been shown to improve compliance so support by the midwife in pregnancy, as part of the multidisciplinary team, is crucially important.
Gene therapy, as an alternative to dietary management, is in the experimental stage and may be available in the future9.
PRE-CONCEPTION ISSUES AND CARE
To prevent maternal PKU syndrome women with PKU are advised to return to the restricted diet when planning to conceive or as soon as possible when pregnant.
This has been shown in many studies to prevent or lessen the effects on the neonate10–12. It can take 1–2 weeks to reduce phenylalanine levels to a therapeutic range of 60–200 mmol/l on commencing the diet.
As many pregnancies are unplanned the advice to remain on the restrictive diet during adulthood6 is important for women of child-bearing age as the aim is to achieve low blood phenylalanine levels early, ideally pre-conception.
- Congenital heart disease13
- Microcephaly
- Cranio-facial abnormalities
- IUGR
- It is important to maintain blood phenylalanine levels at <200 µmol/l3,8
- Untreated levels of phenylalanine of 1200 µmol/l have been reported
- Women who are given increased support tend to attain earlier metabolic control8
- Pre-conception care is essential to optimise maternal levels before conception
- In women with PKU who conceive on normal diets, early recourse to the restrictive diet has been shown to reduce fetal effects
- Referral to a wider multidisciplinary team as necessary, e.g. physician, dietician, geneticist, clinical nurse specialist
- Early booking facilitates first and second trimester screening for associated congenital abnormalities and appropriate counselling
- Serial ultrasound assessment to screen for IUGR
- Twice-weekly phenylalanine self-blood-testing by the woman
- Regular venous blood testing, i.e. Hb, FBC, copper, zinc, selenium, calcium, albumin, phosphates, ferritin, vitamin B12 and tyrosine
- Monthly 24-hour phenylalanine profile
- Support by a known midwife may help dietary compliance rates and attendance at clinics, which will improve pregnancy outcomes16
- Shared care is necessary during the antenatal period
- Place of birth is dependent on presence of fetal complications, e.g. IUGR when birthing in a consultant-led environment with neonatal unit facilities would be advised
- If no complications develop by term then giving birth in a midwifery-led environment may be possible
- Full information on risks and management, both through discussion and in written format should be provided
- If antenatal in-patient care is needed, attendance to diet is vitally important, so seek advice from a dietician on admission
- No significant implications for delivery
- Babies will require neonatal assessment at delivery
- Decisions about the place of birth are dependent upon the presence or absence of complications
- Complications should be managed in accordance with local unit guidelines
- Provide good-quality, midwifery-led care for low-risk women
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