The risks associated with pregnancy in women with pre-existing type 1 and type 2 diabetes are increased for both mother and baby.

Maternal and Fetal Risks

Adverse perinatal outcomes associated with pre-existing type 1 and type 2 diabetes(referred to as pre-Gestational Diabetes Mellitus or pre-GDM) include birth defects affecting, in particular, the cardiac, central nervous and musculoskeletal systems.¹ Perinatal mortality and morbidity is also increased.

In a review of outcomes in pre-GDM pregnancies the risks of pre-term delivery (20%) and macrosomia (35%) were increased 4.5-fold.²

The stillbirth rate was 16/1000 births; this represents a 2.9-fold increased risk compared to non-diabetic pregnancies but compares favourably with internationally reported experience.³

Maternal morbidity may be due to worsening of diabetes-related complications (retinopathy, nephropathy, coronary artery disease) and women with type 2 diabetes often have co-morbidities such as obesity and hypertension that are independently associated with adverse pregnancy outcomes.

Outcomes: Type 1 vs Type 2

In a meta-analysis of maternal and fetal pregnancy outcomes, the risks were found to be similar for type 1 and type 2 diabetes. ⁴ Women with type 2 diabetes were older, more likely to be overweight/obese, had higher rates of hypertension, were less likely to have pre-pregnancy care and booked later for antenatal care.

However, they had a shorter duration of diabetes mellitus, fewer diabetic complications and lower HbA1c levels at booking and throughout the pregnancy.

The risk of perinatal mortality was 1.5-fold greater in type 2 than type 1 diabetes but stillbirth, neonatal and congenital malformation rates were similar for type 1 and type 2 diabetes.

The Importance of Pre- Pregnancy Care

Suboptimal maternal glycaemic control has consistently been associated with increased risks of major congenital malformation and perinatal mortality⁵ and preconception care has been shown to reduce these risks.⁶

International recommendations advise a target HbA1c of <6.1% (NICE 2008)⁷ to <7% (ADA 2008)⁸ if this can be safely achieved. It is strongly advised that women with an HbA_1c >10% avoid pregnancy (NICE 2008).⁷

The management of hyperlipidaemia and hypertension must be reviewed with cessation of statins and adjustment of antihypertensive therapy to non-teratogenic alternatives. Folic acid (5mg) should be recommended for three months prior to conception.

Complications Screening

All women should have micro- and macrovascular complication screening (in type 1 diabetes this includes screening for thyroid and coeliac disease).⁹

Pregnancy is contraindicated for women with untreated active proliferative retinopathy, chronic renal failure or severe autonomic neuropathy and relatively contraindicated for women with established cardiac disease.

Blood Glucose Control

The aim of treatment is to achieve the best control possible while avoiding hypoglycaemia. For type 1 diabetes, intensive insulin therapy (multiple dose regimens or an insulin pump) is standard care.

Short-acting insulin analogs are recommended in pregnancy but the longer acting analogs (detemir, glargine) are not, although they may be continued in some circumstances. In type 2 diabetes the issue of when to commence insulin (pre-conception or upon confirmation of pregnancy), and whether to continue metformin during pregnancy must be individualised and take into consideration the potential weight gain with insulin and the risks of unstable glycaemic control during the transition phase.

Sulphonylureas and other oral hypoglycaemic agents are considered to be contraindicated in pregnancy.

The role of metformin for women with type 2 diabetes, especially those with coexistent PCOS, remains controversial - although some international guidelines now suggest that it may be continued (NICE 2008)7 others do not recommend its use outside of clinical trials.⁹

Diabetes Management During Pregnancy

Where possible, management should involve a multidisciplinary team. Women should be warned that insulin requirements will vary during pregnancy. Hypoglycaemia (especially nocturnal) is common in the first trimester in type 1 diabetes (further complicated by nausea and/or vomiting). Increasing insulin resistance, which occurs in the late second and third trimesters, often results in significant increases in insulin requirements.⁹

Accurate documentation of gestational age and detailed ultrasonographic examination for congenital anomalies are essential. After 28-30 weeks gestation, sequential ultrasound assessment, including umbilical artery blood flow measurement and construction of biophysical profiles, may be indicated. Serial cardiotocography is often performed beginning in the mid-late third trimester.

The timing and mode of delivery will be determined by a number of factors, including glycaemic control, maternal co-morbidities, pregnancy-associated complications (pre-eclampsia), fetal parameters (estimated fetal size, growth and wellbeing) and obstetric history.

Post Partum Care

In type 1 diabetes insulin requirements fall rapidly and often dramatically after delivery with breast feeding reducing this further (by about 20 per cent). Strategies to avoid and manage hypoglycaemia are essential.

Women with type 2 diabetes who require treatment for their hyperglycaemia will usually continue on insulin until breast feeding is completed although metformin may be introduced as only approximately 2% is excreted in breast milk.

 Pregnancy in Patients with Diabetes 222.28 Kb

References

1. Correa A, Gilboa SM, Besser LM, Botto LM, Moore CA, Hobbs CA, Cleves MA, Riehle-Colarusso TJ, Waller K, Reece A and the National Birth Defects Prevention Study. Diabetes mellitus and birth defects Am J Obstet Gynecol 2008.199:237.e2-9

2. Shand AW, Bell JC , McElduff A,  Morris J, Roberts CL. Outcomes of pregnancies in women with pre-gestational diabetes mellitus and gestational diabetes mellitus; a population-based study in New South Wales, Australia, 1998-2002. Diabetic Medicine 2008. 25:708-715

3. Macintosh M,  Fleming K, Bailey J, Doyle P, Modder J, Acolet D, Golightly S, Miller A. Perinatal mortality and congenital anomalies in babies of women with type 1 or type 2 diabetes in England, Wales, and Northern Ireland: population based study. BMJ 2006,333:177-180.

4. Balsells M, Garcia-Patterson A, Gich I and Corcoy R.  Maternal and fetal outcomes in women with type 2 versus type 1 diabetes mellitus : a systematic review and metaanalysis. Journal Clinical Endocrinology and Metabolism 2009 94 (11): 4284-91

5. Inkster ME, Fahey TP, Donnan PT, Leese GP, Mires GJ and Murphy DJ. Poor glycated haemoglobin control and adverse pregnancy outcomes in type 1 and type 2 diabetes mellitus: Systematic review of observational studies. BMC Pregnancy and Childbirth 2006,6:30

6. Ray JG, O'Brien TE, Chan WS. Preconception care and the risk of congenital anomalies in the offspring of women with diabetes mellitus: a meta-analysis. QJM. 2001, 94:435-44

7. Management of diabetes from preconception to the postnatal period: summary of the NICE guidance. BMJ 2008, 336:714-717

8. American Diabetes Association. Standards of Medical Care in Diabetes-2008 [Miscellaneous Article] Diabetes Care. 2008 31 (Supplement 1):S12-S54.

9. Kitzmiller JL, Block JM, Brown FM, Catalano PM, Conway DL, Coustan DR, Gunderson EP, Herman WH, Hoffman LD, Inturrisi M, Jovanovic LB, Kjos SI, Knopp RH, Montoro MN, Ogata ES, Edward S, Paramsothy P, Reader DM, Rosenn BM, Thomas A,  Kirkman M. Managing Preexisting Diabetes for Pregnancy: Summary of evidence and consensus recommendations for care. Diabetes Care 2008, 31(5):1060-1079.

References and further reading available at http://www.medicalobserver.com.au/

Content Updated April 5, 2010