For information about gestational diabetes mellitus, please refer to the section ‘Gestational diabetes mellitus’.
Pregnancy with pre-existing diabetes
Sub-optimal glycaemic management at conception and early in pregnancy is associated with increased risk of congenital malformations and first trimester miscarriages.
Women with pre-existing diabetes (types 1 and 2) are more prone to the complications of pregnancy such as higher rates of pre-eclampsia prematurity and caesarean section.16 In addition, pregnancy may accelerate maternal complications of diabetes, such as diabetic retinopathy (see the section ‘Microvascular complications: Diabetes-related eye disease’).17 Both maternal and fetal complications are increased by diabetes. Risk is progressive with increasing glycaemia.18
Optimising glycaemic management can mitigate these risks, the likelihood of birth trauma, and the risk of early induction of labour and need for caesarean section.
Women of reproductive age with existing diagnoses of diabetes should be advised of the benefits of contraception to prevent inadvertent pregnancy before glycaemia can be optimised. Women should be advised of the need for advice, education and support to achieve optimal glycaemic control before pregnancy.
Women with type 2 diabetes and polycystic ovary syndrome or irregular periods must be advised that improved fertility may accompany use of therapies, including metformin.
Where possible and practicable, formal, diabetes-specific pregnancy planning should occur prior to pregnancy.
This should be patient-focused, support self-management and involve a multidisciplinary team. Planning should include assessment of diabetes-related complications, review of all medications and commencement of folic acid (no more than 5 mg/day).4
Deferring pregnancy should be recommended until glycaemic control is optimal. Women should be reassured that any reduction in glycated haemoglobin (HbA1c) towards the individualised target is likely to reduce the risk of congenital malformations.
Refer to the NDSS for advice on pre-pregnancy blood glucose targets.
Medications should be reviewed and ceased or replaced as appropriate, ideally before pregnancy during the planning period, or urgently once pregnancy is confirmed. Consultation with local specialist services is advised. Agents such as sulfonylureas, glitazones, SGLT2 inhibitors and incretin-based therapies will need to be reviewed or ceased, and insulin therapy instituted.
Table 1 presents safety profiles and advice for diabetes medications in pregnancy.
Practice Points: Before and during pregnancy
- Counsel the patient that the risks associated with diabetes in pregnancy can be reduced, but not eliminated.
- Recommend a reliable form of contraception until blood glucose control is optimised.
- Advise that optimising HbA1c with a balanced diet, physical activity, healthy weight management and appropriate diabetes medication may positively affect pregnancy outcomes.
- Review sick day management plans, and discuss the need for insulin therapy possibly prior to conception and throughout the pregnancy.
- Revise hypoglycaemia prevention and management.
- Advise that nausea and vomiting in pregnancy may affect blood glucose control.
- Aim for blood glucose to be as close to the normal (non-diabetic) range as possible, ensuring risks of maternal hypoglycaemia are minimised. This reduces risk of spontaneous abortion, congenital abnormalities, pre-eclampsia, retinopathy progression and stillbirth.1
- Review self-monitoring of blood glucose (SMBG) and/or continuous glucose monitoring (CGM) to determine if medication adjustment and/or commencement of insulin is required, and assess risk of hypoglycaemia. Some patients may be eligible for NDSS-subsidised access.
- Recommend higher folate supplementation (up to 5 mg per day), starting one month before pregnancy4 and continuing until 12 weeks of gestation, to reduce the risk of neural tube defects.
- Be aware that women treated for hypothyroidism may require higher doses of thyroid hormone replacement therapy. Based on reassessment, a suggested dose change is an increase of 30% once there is a positive pregnancy test (eg if on one tablet per day, increase by two tablets per week).19
- Advise examination of the retina prior to conception and during each trimester for women with types 1 and 2 diabetes. More frequent assessment may be required if retinopathy is present. Patients with active, moderate–severe non-proliferative retinopathy or with proliferative retinopathy who have not had an ophthalmological assessment within the preceding six months should undergo testing prior to pregnancy to see if the retinopathy is stable enough for pregnancy.
- Test renal function if this has not been done within the preceding three months. Elevated creatinine or estimated glomerular filtration rate (eGFR) <45 mL/min/1.73 m2 or an albumin-to-creatinine ratio >30 mg/mmol is an indication for pre-pregnancy nephrology assessment.20
Safety and risks of common diabetes medications before and during pregnancy
Insulin therapy will need regular review and titration to achieve glycaemic goals.
Intensive glycaemic control guided by SMBG or CGM, versus SMBG alone, has been shown to improve neonatal outcomes in type 1 diabetes in pregnancy.24 However, studies that included people with type 2 diabetes in pregnancy have failed to demonstrate this benefit.25
Close surveillance for new diabetes complications and monitoring of existing complications should occur routinely.
GPs should provide timely and appropriate support and referral for women who are experiencing an unplanned pregnancy where risks of abnormal pregnancy outcomes are elevated.
Ultrasound screening is advised at 10–13 weeks’ gestation (with biochemistry) for trisomies, and at 18–20 weeks for congenital cardiac and other malformations. Pregnant women with diabetes should be offered ultrasound monitoring of fetal growth and amniotic fluid volume every four weeks from 28–36 weeks.20 Fetal growth and wellbeing monitoring should occur under specialist supervision. It is recommended to refer to your local specialist endocrine and obstetric services.
Patients should be referred to specialised diabetes antenatal care as soon as possible, as multidisciplinary shared care is considered best practice.20 A multidisciplinary team ideally involves:
- credentialled diabetes educator
- accredited practising dietitian
The GP should maintain or re-establish contact with mother and child as early as practicable to address any issues arising from the pregnancy, labour, surgery or breastfeeding and to review medications.
Metformin may be continued while breastfeeding with minimal effect on the baby.26 Breastfeeding may alter glucose levels, so glycaemic monitoring, oral medications and insulin need careful review during breastfeeding to minimise the risk of hypoglycaemia.
Re-establishing glycaemic management goals, reassessment of complications and timely contraceptive advice are also appropriate in the postpartum period.