Gestational diabetes

Gestational diabetes

Gestational diabetes the silent epidemic

Obese women and certain ethnic groups are amongst those at heightened risk of Gestational Diabetes Mellitus, an epidemic that is causing worldwide concern. Expert Dr Elizabeth Stenhouse explains how midwives can best help to identify and manage the condition and also explains how important prevention strategies are to both maternal and fetal health Dr Elizabeth Stenhouse RGN RM PhD Associate Professor, Midwifery Research, School of Nursing and Midwifery, Faculty of Health Education and Society, Plymouth University, Devon

W

hat is Gestational Diabetes Mellitus?

In normal pregnancy a number of maternal metabolic modifications occur in order to meet the energy requirements of the growing fetus. During the last trimester of pregnancy the demand for glucose from the growing fetus increases and in order to meet this demand there is a decrease in maternal insulin sensitivity and increase in insulin resistance. This enables more glucose to be released and pass to the fetus. The maternal response to the decrease in insulin sensitivity and an increase in insulin resistance is to produce more insulin. However some pregnant women are unable to increase insulin production in response to the insulin resistance, and consequently become hyperglycaemic. These elevated glucose levels may lead to Gestational Diabetes Mellitus (GDM) which has been defined as ‘carbohydrate intolerance of variable severity with onset during pregnancy with return to normal after delivery’ (Scott et al, 2002).

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Gestational diabetes The incidence and prevalence of GDM It is undisputed that there is a global and national obesity epidemic, which is also reflected in women of reproductive age. Simmons (2011) suggests that alongside the obesity epidemic is ‘a diabetes pandemic including growing numbers of women with GDM’, as a high proportion of women with GDM are obese and a significant percentage of those who are obese have GDM. The conditions of GDM and obesity are now seen as a major public health problem, and according to Diabetes UK (2011) GDM can affect up to 5% of all pregnancies, being more prevalent in certain ethnic groups.

Who is most at risk of GDM? The women most at risk of GDM are those with a BMI >30kg/m2, women who have previously given birth to a macrosomic baby weighing ≥4.5kg, women with a history of GDM in a previous pregnancy, and those with a first-degree relative with diabetes, whose family origin also has a high prevalence of diabetes. Women with Polycystic Ovary Syndrome also have an increased risk of developing GDM in pregnancy. Ethnicity is an important consideration too as women of South Asian, black Caribbean and Middle Eastern origin are at higher risk of developing GDM. Interestingly, deprivation has been indicated as another risk factor for GDM as poverty is linked to obesity and consequently to GDM (Lega et al, 2011). In practice, other risk factors may be included that reflect the local population, or are deemed clinically relevant such as glycosuria.

How is it diagnosed? GDM is generally asymptomatic and so women will have few symptoms. However, the most frequently used method of diagnosis is by risk factor assessment as detailed in NICE guidelines 63 (2006) (see Table 1). It can also be diagnosed by biochemical examinations of the blood (Buchanan & Xiang, 2005).

If women have one or more risk factors, a diagnostic twohour 75g oral glucose tolerance test (OGTT) is undertaken, with a diagnosis made using the criteria defined by the World Health Organization (2006), as below: Fasting venous plasma glucose ≥7 mmol/L and Two hour Plasma glucose ≥7.8 mmol/L.

How should GDM be managed? Management of expectant mothers presenting with symptoms which raise a suspicion of a GDM diagnosis very much depends on whether this is a first diagnosis, or whether the mother has previously been diagnosed with the condition. The latter means she is at higher risk of developing GDM during her pregnancy. Women with previous pregnancies complicated by Gestational Diabetes Mellitus

Women diagnosed with GDM in a previous pregnancy should be given self-monitoring of blood glucose (SMBG) equipment in early pregnancy or undergo an OGTT at 16 to 18 weeks gestation. The OGTT will be diagnostic of those women who may have developed type 2 diabetes prior to pregnancy. Some women may have impaired glucose tolerance but not be within diabetic range and this will be identified by SMBG at an early stage of pregnancy and given appropriate treatment and advice. However, if the OGTT is normal and SMBG is within the target levels a further OGTT at 28 weeks will be undertaken. Women diagnosed with Gestational Diabetes Mellitus in current pregnancy

Women diagnosed with GDM will be instructed on how to do SMBG and given targets for blood glucose control. These targets are usually 5.5mmol/l or below pre-prandial and < 7.0mmol/l post prandial. In addition to the normal advice given by the midwife, further information related to the risks of excessive gestational 16

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Gestational diabetes Picking up signs of GDM during a first pregnancy Katie is pregnant with her first baby. At her first six-week gestation appointment with the midwife her BMI was calculated and found to be 30, which is regarded as clinically obese. After advising Katie of her BMI classification the midwife gave her advice regarding healthy eating and exercise (NICE, 2008). Katie’s pregnancy progressed normally but due to her raised booking BMI Katie was advised to have a 2\-hour 75 g OGTT to test for GDM between 24–28 weeks. The midwife discussed the implications of a diagnosis for Katie and her baby with both Katie and her partner. The test was performed and the following day the diagnosis of GDM was made using the criteria defined by the World Health Organization (WHO). Katie was seen in the combined diabetic antenatal clinic at the earliest appointment. Here she was taught self-monitoring of her blood glucose levels and targets levels for blood glucose control were given. Katie and her partner were also seen by the Diabetes Specialist Midwife (DSM) who explained that the first line of treatment would be dietary and exercise advice along with self-monitoring of blood glucose levels At the next appointment (29 weeks gestation) Katie’s blood glucose levels were raised so she was prescribed an oral hypoglycaemic agents.

weight gain, diet and the benefits of exercise will be offered. This may be given by a midwife or an appropriately trained healthcare professional such as a dietitian (Major et al, 1998; Avery et al, 1997).

What are the best recommended treatments? Although lifestyle modification is often the first line treatment for women, diet and exercise alone may not keep blood glucose levels within the target range and medication may be required. Oral hypoglycaemic agents such as metformin or glibenclamide can be effective in the treatment of women with hyperglycaemia (Simmons et al, 2004). Some women may fail to achieve adequate glycaemic control, so remain hyperglycaemic and require insulin therapy. In pregnancy, the most commonly used insulins are the rapid-acting insulin analogues aspart and lispro. However, all treatments should be individually tailored to the woman’s needs and be acceptable to both herself and her partner.

GDM and adverse pregnancy outcomes

The DSM also gave Katie information related to the effect high glucose levels may have on the baby if Katie’s blood glucose levels were not controlled, and explained that if the baby grew large for its gestational age there was an increased risk of interventions such as induction of labour or caesarean section. The DSM highlighted that there was a small risk of birth complications such as shoulder dystocia and neonatal hypoglycaemia. Katie had further antenatal appointments at the combined antenatal clinic, the pregnancy was monitored and fetal growth assessed by two weekly ultrasound scans. Katie was managing her diet, medication and self-monitoring of blood glucose levels. All was progressing well. At 36 weeks gestation the fetal growth scan highlighted that the baby had grown above the 95th centile and a further scan was performed at 38 weeks, which showed continued growth above the 95th centile. It was agreed after consultation with the obstetrician and in discussion with Katie and her partner that the pregnancy would be induced. Katie was admitted for induction following the local hospital guidelines. As the pregnancy was complicated by GDM, the fetus was monitored throughout her labour as were Katie’s blood glucose levels. Following a 16 hour labour Katie gave birth naturally to a baby boy (Jack) weighing 4.23kgs. Jack was breast-fed within an hour of his birth and a post feed blood glucose was taken and found to be within normal limits. Katie’s performed a SMBG which was also within normal limits. The following day Katie and Jack were discharged into the care of the community midwife. The practice nurse at the local GP surgery gave Katie dietary and exercise advice at the six week post birth visit. Katie was seen annually and screened for T2DM via a fasting blood glucose. Jack was breast-fed exclusively until he was weaned at six months.

As GDM is one of the most common complications of pregnancy there is well documented evidence of an increase of adverse pregnancy outcomes for the mother and infant. For the mother there is an increased risk of pre-eclampsia and pregnancy induced hypertension (Bryson et al, 2003). Adverse pregnancy outcomes are is also associated with fetal macrosomia, defined as fetal weight ≥ 95 centile, which may necessitate labour to be induced. Women with GDM are also at increased risk of having a caesarean section. Birth trauma during normal birth may be perineal-based and result in third and fourth degree tears (Bentley-Lewis, 2009).

What are the effects of GDM on the infant? If not treated or well controlled, GDM may lead to a macrosomic baby and birthing a ‘large’ baby can cause an unexplained death in utero, prolonged labour, www.jfhc.co.uk © Journal of Family Health Care Vol 23 No 6

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Gestational diabetes shoulder dystocia and as a consequence, fetal asphyxia, clavicle fracture and/or Erb’s palsy (Dang et al, 2000). Post birth, the neonate is at greater risk of hypoglycaemia, hypertrophic cardiomyopathy and hyperbilirubinemia (Perkins et al, 2007). These conditions may require the baby to be admitted to the neonatal/special care unit and this should be discussed with the woman and her partner during the antenatal period.

Future health outcomes following a pregnancy complicated by GDM Women with pregnancies complicated by GDM are at increased risk of GDM in future pregnancies, especially if she continues to be overweight and obese. Extensive research has shown that four to 10% of women who have had GDM in pregnancy can develop type 2 diabetes mellitus (T2DM) within nine months post pregnancy (Bellamy et al, 2009). Further evidence shows that conversion to T2DM can occur within the first five years post birth (Collier et al, 2011; Kim et al, 2002). For the offspring of a mother who has had a pregnancy complicated by GDM there is increasing evidence that the child undergoes metabolic adaptation in utero in response to maternal hyperglycaemia (Osgood et al, 2011; Egeland & Meltzer, 2010). Consequently, it is thought that this predisposes them to future obesity and T2DM in child and adulthood, continuing the cycle of obesity and diabetes (Dornhorst, 2003; Dabelea et al, 2008).

Conclusion Preventing excessive birth weight is the primary goal of a clinician caring for women with pregnancies complicated by GDM. The prevalence of GDM and obesity is increasing in the UK and globally the consequences for the health of mother and child, both short and long term, are well researched. Interventions for primary prevention of GDM is a major objective for clinicians caring for women with and post GDM. A review by Oostdam et al (2011) investigating the benefits of dietary counselling and exercise programs for preventing GDM and T2DM post birth showed these interventions may be effective. It is undisputed that obesity is rising in women of reproductive age and until the causes of obesity are addressed there will be a continuing rise in the numbers of pregnancies complicated by GDM.

Table 1 Risk factors for gestational diabetes Body mass index above 30 kg/m2

References Avery MD, Leon AS & Kopher RA (1997) Effects of a partially home-based exercise program for women with gestational diabetes. Obstetrics and Gynecology 89 10–15. Bellamy L, Casas J-P, Hingorani AD & Williams D (2009) Type 2 diabetes mellitus after gestational diabetes: a systematic review and meta-analysis. The Lancet 373 1773–1779. Bentley-Lewis R (2009) Gestational diabetes mellitus: an opportunity of a lifetime. The Lancet 373 1738–1740. Bryson C, Ioannou G, Rulyak S & Critchlow C (2003) Association between gestational diabetes and pregnancy-induced hypertension. American Journal Epidemiology 158 1148–1153. Buchanan TA & Xiang, AH (2005) Gestational Diabetes Mellitus. Journal of Clinical Investigation 115 485-491. Collier SA, Mulholland C, Williams J, Mersereau P, Turay K & Prue C (2011) A Qualitative Study of Perceived Barriers to Management of Diabetes Among Women with a History of Diabetes During Pregnancy. Journal of Women’s Health 20 1333–9. Dabelea D, Mayer-Davis EJ, Lamichhane AP, D’Agostino RB Jr, Liese AD, Vehik KS, Narayan KMV, Zeitler P & Hamman RF (2008) Association of Intrauterine Exposure to Maternal Diabetes and Obesity With Type 2 Diabetes in Youth: The SEARCH Case-Control Study. Diabetes Care 31 1422–1426. Dang K, Homko C & Reece AE (2000) Factors associated with fetal macrosomia in offspring of gestational diabetic women. Journal of Maternal and Fetal Medicine 9 114–117. Diabetes UK (2011) Diabetes in the UK [online]. London: Diabetes UK. Available at: www.diabetes.org. uk (accessed August 2013) Dornhorst A (2003) Maternal hyperglycaemia: food for thought. Practical Diabetes Intentional 20 283–289. Egeland G & Meltzer S (2010) Following in mother’s footsteps? Mother-daughter risks for insulin resistance and cardiovascular disease 15 years after gestational diabetes. Diabetic Medicine 27 257–265. Kim C, Newton K & Knopp R (2002) Gestational diabetes and the incidence of type 2 diabetes: a systematic review. Diabetes Care 25 1862–1868. Lega I, Ross NA, Zhong L & Dasgupta K (2011) Gestational Diabetes History May Signal Deprivation in Women with Type 2 Diabetes. Journal of Women’s Health 20 625–629. Major CA, Henry MJ, De Veciana M & Morgan MA (1998) The effects of carbohydrate restriction in patients with diet-controlled gestational diabetes. Obstetrics and Gynecology 91 600–604. National Institute for Health and Clinical Excellence (2006) NICE clinical guideline 63: Diabetes in pregnancy. Management of diabetes and its complications from pre-conception to the postnatal period. London: NICE National Institute for Health and Clinical Excellence (2008) NICE clinical guideline 62: Antenatal Care. London: NICE

Previous macrosomic baby weighing 4.5 kg or above

Oostdam N, van Poppel MNM, Wouters MGA & van Mechelen W (2011) Interventions for Preventing Gestational Diabetes Mellitus: A Systematic Review and Meta-Analysis. Journal of Women’s Health 20 1551–1563.

Previous gestational diabetes

Osgood ND, Dyck RF & Grassmann WK (2011) The Inter-and Intra-generational Impact of Gestational Diabetes on the Epidemic of Type 2 Diabetes. American Journal of Public Health 101 173–179.

Family history of diabetes (first-degree relative with diabetes)

Perkins JM, Dunn JP & Jagasia SM (2007) Perspectives in Gestational Diabetes Mellitus: A Review of Screening, Diagnosis, and Treatment. Clinical Diabetes 25 57–62.

Family origin with a high prevalence of diabetes: ●● South Asian (specifically women whose country of family origin is India, Pakistan, Bangladesh) ●● Black Caribbean ●● Middle Eastern (specifically women whose country of family origin is Saudi Arabia)

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Scott DA, Loveman E, McIntyre L & Waugh N (2002) Screening for gestational diabetes: a systematic review and economic evaluation. Health Technology Assessment 6 1–161. Simmons D, Walters B, Rowan JA & McIntyre HD (2004) Metformin therapy and diabetes in pregnancy. Medical Journal of Australia 180 462–464. Simmons D (2011) Diabetes and obesity in pregnancy. Best Practice & Research Clinical Obstetrics & Gynaecology 25 25-–36. World Health Organisation (2006) Diabetes [online] www/who.int/diabetes/publications.new.pdf (assessed August 2013)

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