Diabetes in Pregnancy
Diabetes in Pregnancy
Most cases of diabetes in pregnancy are seen in patients who were diabetic pre-conception. However, gestational diabetes is when the onset of diabetes is during the pregnancy. In most cases the diabetes resolves along with the pregnancy but some will remain diabetic after the delivery and there is in those who resolve there is an increased lifetime risk of developing type 2 diabetes.
Screened for with routine urine dipsticks at each antenatal visit.
- If glycosuria is detected then random blood glucose levels should be taken.
- If fasting random blood glucose concentration is >7.0 mmol/l then diabetes is diagnosed
- If random blood glucose concentrations are >6.1 mmol/l fasting (>2hrs after food) or >7.0 mmol/l if <2hrs after food then, then an oral glucose tolerance test should be performed.
- If blood glucose concentration is >7.8 mmol/l following oral glucose tolerance test, then diabetes is diagnosed.
At 6 weeks postpartum a further oral glucose tolerance test should be undertaken to see whether the gestational diabetes has resolved. Whatever the result, however, these women are at an increased risk of developing diabetes for life. Therefore, not only should they be monitored closely in subsequent pregnancies, but should also be offered lifestyle advice and fasting blood glucose concentration testing annually.
Risk factors for Gestational Diabetes
- BMI >30
- Previous macrosomic baby weighing >4.5 kg
- PMH of gestational diabetes
- FH of type 1/type 2 diabetes (first degree relative)
- Ethnicity (South Asian, Black Caribbean, Middle Eastern)
- Previous stillbirth that was unexplained
Prior to conception, the focus should be on information, advice and support. Avoidance of unplanned pregnancy can help achieve optimum outcomes. The diabetic woman should aim for an HBA1c of <6.1% prior to conception, and patients with an HBA1c of >10% are strongly recommended to avoid pregnancy. This improved glycaemic control can reduce the risks of stillbirth, miscarriage, congenital malformation and neonatal death. The need to take 5 mg folic acid daily should be underlined during pre-conception counselling, in order to reduce the risk of neural tube defects.
Oral hypoglycaemic agents (except metformin) should be stopped prior to conception, along with statins and ACE inhibitors. Patients with a BMI >27 should be offered advice on losing weight prior to conceiving a child, according to NICE guidance.Information should be supplied concerning:
- Weight loss methods
- Diabetic neuropathy can worsen during pregnancy
- Nausea and vomiting, common in pregnancy, can have an effect on glycaemic control
- Risks associated with diabetes in pregnancy (detailed below)
But bear in mind that this is the ideal situation and may not always be the case.
NICE advice to diabetic women planning a pregnancy
- Risks associated with pregnancies complicated by diabetes increase with the duration of diabetes
- To use contraception until good glycaemic control has been established
- Glycaemic targets, glucose monitoring and medication will need to be reviewed before and during pregnancy
- Additional time and effort needed to manage diabetes during pregnancy and will therefore require more contact with HCPs
- BMI >27 should be offered advice on weight loss
- Diabetic women planning to become pregnant should take folic acid 5 mg until 12wks gestations
Blood glucose monitoring:
- Monthly measurement of HbA1c
- Given a meter for self-monitoring
- Self monitoring should be increased from normal levels
- If DM type 1, should be given ketone testing strips to test for ketonuria or ketonaemia if they become unwell or hyperglycaemic
- Diabetic women should be offered retinal assessment pre conception, and annually thereafter.
Main aims are good diabetic control and regular ultrasound scans of the fetus.
Medical management of gestational diabetes is very similar to normal diabetes; mothers can be given oral hypoglycaemic agents such as metformin as can insulin. A Cochrane review found that dietary advice had little impact on development or complications of gestational diabetes. The mother's insulin requirement increases by 100% during pregnancy. Medical management should be considered:
- If diet and exercise fail to maintain blood glucose targets for a period of 1–2 weeks.
- If ultrasound scan suggests incipient fetal macrosomia (abdominal circumference >70th centile)
Target ranges for blood glucose (if safely achievable):
- Fasting glucose between 3.5 and 5.9 mmol/l
- <7.8 mmol/l 1 hour after food
HbA1c should not be used routinely in the second and third trimesters of pregnancy
Extra ultrasound scans should be offered:
- Scan for congenital malformations of heart – an ultrasound examination of the four chambers of the heart at 18-20wks
- Serial growth scans every 4 weeks from 28 to 36wks
- Antenatal steroids for preterm labour can be given, but require additional insulin and be closely monitored
- Diabetes is not a contraindication for vaginal delivery
- Should be offered elective induction (or caesarean if indicated) after 38wks gestation
As retinopathy can also worsen 3 monthly checks can be offered to help reduce damage caused by retinopathy.
Complications of Diabetes in Pregnancy
- Increased risk of hypoglycaemic episodes
- Increased risk of preterm labour, stillbirth and miscarriage
- Trauma to birth canal due to large baby (macrosomia) with increased risk of third degree tears
- Congenital abnormalities (10x), particularly:
- Neural tube defects
- Hypoxia and sudden intrauterine death after 36wks gestation
- Increased risk of sacral agenesis
- Neonatal hypoglycaemia risk is increased - chronically raised glucose in pregnancy causes fetal hyperinsulinaemia, leading to poor insulin control in the new-born.
- Low calcium
- Increased risk of polycythaemia
- Respiratory distress syndrome – immature lungs due to poor surfactant production and reduced cortisol levels
- Jaundice – low cortisol levels reduce hepatic enzymes, therefore raising bilirubin levels
- Tieu J, Shepherd E, Middleton P, Crowther CA. Dietary advice interventions in pregnancy for preventing gestational diabetes mellitus. Cochrane Database of Systematic Reviews2017, Issue 1. Art. No.: CD006674. DOI: 10.1002/14651858.CD006674.pub3.