Pre-existing Type 2 Diabetes in Pregnancy

Preexisting type 2 diabetes in pregnancy is insulin resistant diabetes present before conception, usually with obesity. It is rising in frequency, and is often undiagnosed until booking. High glucose and obesity raise the risk of congenital anomaly, miscarriage, stillbirth, macrosomia, preeclampsia and caesarean birth.

• Risk factors: body mass index above 30 kg/m2, family history, previous gestational diabetes, polycystic ovary syndrome, HIV on some antiretrovirals.
• Insulin needs are high, often 0.8 to 1.5 units/kg daily.
• Many women are on drugs that must be stopped before conception.

Women are often overweight and may have hypertension, acanthosis nigricans, polyuria, recurrent candidiasis or no symptoms. Examine blood pressure, weight, fundi, feet and fundal height.

• Large fundal height for dates.
• Recurrent vulvovaginal candidiasis and urinary infections.
• Differential diagnosis: gestational diabetes, type 1 diabetes, monogenic diabetes, steroid induced hyperglycaemia, Cushing syndrome.
• Complications: congenital anomaly, preeclampsia, macrosomia, polyhydramnios, shoulder dystocia, stillbirth, caesarean birth, ketoacidosis, retinopathy progression, neonatal hypoglycaemia.

The approach is to confirm control, screen for complications and measure fetal growth.

• Fasting plasma glucose 7.0 mmol/L or above, random glucose 11.1 mmol/L or above, or HbA1c 6.5 percent or above confirms diabetes at booking.
• Glucose targets: fasting 3.5 to 5.3 mmol/L, 1 hour after meals below 7.8 mmol/L, 2 hours below 6.4 mmol/L.
• HbA1c at booking and every 4 to 8 weeks; urine albumin to creatinine ratio; creatinine; lipid profile; retinal examination at booking and 28 weeks.
• Ultrasound for dating, anomaly scan at 18 to 20 weeks, fetal heart scan at 20 to 22 weeks, growth scans every 4 weeks from 28 weeks.

The principle is tight glucose control with metformin and insulin, weight management and planned delivery.

• Supportive: diet of 3 meals and 2 to 3 snacks with 40 to 45 percent carbohydrate; walking 30 minutes daily; weight gain of 5 to 9 kg if body mass index is above 30 kg/m2; stop smoking and alcohol.
• Pharmacological: folic acid 5 mg oral daily from preconception to 12 weeks; aspirin 150 mg oral at night from 12 weeks to 36 weeks; metformin 500 mg oral with meals increased to 1 g 12-hourly (maximum 2.5 g daily); add isophane insulin 0.2 units/kg subcutaneous at bedtime and soluble insulin 0.1 units/kg subcutaneous before each meal, titrated by 2 units every 2 to 3 days; stop sulfonylureas, SGLT2 inhibitors, GLP-1 agonists, statins, ACE inhibitors and angiotensin receptor blockers and use methyldopa 250 to 500 mg oral 8-hourly (maximum 3 g daily) or nifedipine modified release 30 to 60 mg daily for blood pressure above 140/90 mmHg; betamethasone 12 mg IM twice, 24 hours apart, if delivery is needed before 34 weeks with insulin increased by 25 to 40 percent for 72 hours.
• Procedures: induction of labour or caesarean section at 37 weeks to 38 weeks and 6 days; caesarean section if estimated fetal weight is above 4500 g; in labour check glucose hourly (target 4 to 7 mmol/L) and give soluble insulin infusion 1 to 2 units/hour with dextrose 5 percent if above 7 mmol/L.
• Special groups: after delivery stop insulin and restart metformin 500 mg to 1 g 12-hourly, which is compatible with breastfeeding; neonates feed within 30 minutes, check glucose at 2 to 4 hours, and treat glucose below 2.6 mmol/L with dextrose 10 percent 2 mL/kg IV over 10 minutes; nephropathy and retinopathy need earlier review and laser treatment where proliferative.
• Red flags: glucose above 15 mmol/L, ketones, vomiting, blood pressure above 140/90 mmHg, reduced fetal movements.
• Follow-up: review every 2 weeks; HbA1c every 4 to 6 weeks; contraception; review at 6 weeks; annual HbA1c, eye, kidney and foot checks.