Treatments to improve pregnancy outcomes for women who develop diabetes during pregnancy: an overview of Cochrane systematic reviews

What is the issue?

The aim of this Cochrane overview was to provide a summary of the effects of interventions for women who develop diabetes during pregnancy (gestational diabetes mellitus, GDM) and the effects on women's health and the health of their babies. We assessed all relevant Cochrane Reviews (date of last search: January 2018).

Why is this important?

GDM can occur in mid-to-late pregnancy. High blood glucose levels (hyperglycaemia) possibly have negative effects on both the woman and her baby's health in the short- and long-term.

For women, GDM can mean an increased risk of developing high blood pressure and protein in the urine (pre-eclampsia). Women with GDM also have a higher chance of developing type 2 diabetes, heart disease, and stroke later in life. Babies born to mothers with GDM are at increased risk of being large, having low blood glucose (hypoglycaemia) after birth, and yellowing of the skin and eyes (jaundice). As these babies become children, they are at higher risk of being overweight and developing type 2 diabetes.

Several Cochrane Reviews have assessed different interventions for women with GDM. This overview brings these reviews together. We looked at diet, exercise, drugs, supplements, lifestyle changes, and ways GDM is managed or responded to by the healthcare team.

What evidence did we find?

We found 14 Cochrane systematic reviews and included 10 reviews covering 128 studies in our analysis, which included a total of 17,984 women, and their babies. The quality of the evidence ranged from very low to high.

We looked at:

Dietary interventions (including change to low or moderate glycaemic index (GI) diet, calorie restrictions, low carbohydrate diet, high complex carbohydrate diet, high saturated fat diet, high fibre diet, soy-protein enriched diet, etc.)

We found there were not enough data on any one dietary intervention to be able to say whether it helped or not.

Exercise programmes (including brisk walking, cycling, resistance circuit-type training, instruction on active lifestyle, home-based exercise programme, 6-week or 10-week exercise programme, yoga, etc.)

Similarly, there were not enough data on any specific exercise regimen to say if it helped or not.

Taking insulin or other drugs to control diabetes (including insulin and oral glucose lowering drugs).

Insulin probably increases the risk of high blood pressure and its problems in pregnancy (hypertensive disorders of pregnancy) when compared to oral therapy (moderate-quality evidence).

Supplements (myo-inositol given as a water-soluble powder or capsule).

We found there was not enough data to be able to say if myo-inositol was helpful or not.

Lifestyle changes which combine two or more interventions such as: healthy eating, exercise, education, mindfulness eating (focusing the mind on eating), yoga, relaxation, etc.

Lifestyle interventions may be associated with fewer babies being born large (moderate-quality evidence) but may result in an increase in inductions of labour (moderate-quality evidence).

Management strategies (including early birth, methods of blood glucose monitoring).

We found little data for strategies which included planned induction of labour or planned birth by caesarean section, and there was no clear difference in outcomes among these care plans. Similarly, we found no clear difference among outcomes for different methods of blood glucose monitoring.

What does this mean?

There are limited data on the various interventions. Lifestyle changes (including as a minimum healthy eating, physical activity, and self-monitoring of blood sugar levels) was the only intervention that showed possible health improvements for women and their babies. Lifestyle interventions may result in fewer babies being large. Conversely, in terms of harms, lifestyle interventions may also increase the number of inductions. Taking insulin was also associated with an increase in hypertensive disorders, when compared to oral therapy. There was very limited information on long-term health and health services costs. Women may wish to discuss lifestyle changes around their individual needs with their health professional. Further high-quality research is needed.

Authors' conclusions: 

Currently there is insufficient high-quality evidence about the effects on health outcomes of relevance for women with GDM and their babies for many of the comparisons in this overview comparing treatment interventions for women with GDM. Lifestyle changes (including as a minimum healthy eating, physical activity and self-monitoring of blood sugar levels) was the only intervention that showed possible health improvements for women and their babies. Lifestyle interventions may result in fewer babies being large. Conversely, in terms of harms, lifestyle interventions may also increase the number of inductions. Taking insulin was also associated with an increase in hypertensive disorders, when compared to oral therapy. There was very limited information on long-term health and health services costs. Further high-quality research is needed.

Read the full abstract...
Background: 

Successful treatments for gestational diabetes mellitus (GDM) have the potential to improve health outcomes for women with GDM and their babies.

Objectives: 

To provide a comprehensive synthesis of evidence from Cochrane systematic reviews of the benefits and harms associated with interventions for treating GDM on women and their babies.

Methods: 

We searched the Cochrane Database of Systematic Reviews (5 January 2018) for reviews of treatment/management for women with GDM. Reviews of pregnant women with pre-existing diabetes were excluded.

Two overview authors independently assessed reviews for inclusion, quality (AMSTAR; ROBIS), quality of evidence (GRADE), and extracted data.

Main results: 

We included 14 reviews. Of these, 10 provided relevant high-quality and low-risk of bias data (AMSTAR and ROBIS) from 128 randomised controlled trials (RCTs), 27 comparisons, 17,984 women, 16,305 babies, and 1441 children. Evidence ranged from high- to very low-quality (GRADE). Only one effective intervention was found for treating women with GDM.

Effective

Lifestyle versus usual care

Lifestyle intervention versus usual care probably reduces large-for-gestational age (risk ratio (RR) 0.60, 95% confidence interval (CI) 0.50 to 0.71; 6 RCTs, N = 2994; GRADE moderate-quality).

Promising

No evidence for any outcome for any comparison could be classified to this category.

Ineffective or possibly harmful

Lifestyle versus usual care

Lifestyle intervention versus usual care probably increases the risk of induction of labour (IOL) suggesting possible harm (average RR 1.20, 95% CI 0.99 to 1.46; 4 RCTs, N = 2699; GRADE moderate-quality).

Exercise versus control

Exercise intervention versus control for return to pre-pregnancy weight suggested ineffectiveness (body mass index, BMI) MD 0.11 kg/m², 95% CI -1.04 to 1.26; 3 RCTs, N = 254; GRADE moderate-quality).

Insulin versus oral therapy

Insulin intervention versus oral therapy probably increases the risk of IOL suggesting possible harm (RR 1.3, 95% CI 0.96 to 1.75; 3 RCTs, N = 348; GRADE moderate-quality).

Probably ineffective or harmful interventions

Insulin versus oral therapy

For insulin compared to oral therapy there is probably an increased risk of the hypertensive disorders of pregnancy (RR 1.89, 95% CI 1.14 to 3.12; 4 RCTs, N = 1214; GRADE moderate-quality).

Inconclusive

Lifestyle versus usual care

The evidence for childhood adiposity kg/m² (RR 0.91, 95% CI 0.75 to 1.11; 3 RCTs, N = 767; GRADE moderate-quality) and hypoglycaemia was inconclusive (average RR 0.99, 95% CI 0.65 to 1.52; 6 RCTs, N = 3000; GRADE moderate-quality).

Exercise versus control

The evidence for caesarean section (RR 0.86, 95% CI 0.63 to 1.16; 5 RCTs, N = 316; GRADE moderate quality) and perinatal death or serious morbidity composite was inconclusive (RR 0.56, 95% CI 0.12 to 2.61; 2 RCTs, N = 169; GRADE moderate-quality).

Insulin versus oral therapy

The evidence for the following outcomes was inconclusive: pre-eclampsia (RR 1.14, 95% CI 0.86 to 1.52; 10 RCTs, N = 2060), caesarean section (RR 1.03, 95% CI 0.93 to 1.14; 17 RCTs, N = 1988), large-for-gestational age (average RR 1.01, 95% CI 0.76 to 1.35; 13 RCTs, N = 2352), and perinatal death or serious morbidity composite (RR 1.03; 95% CI 0.84 to 1.26; 2 RCTs, N = 760). GRADE assessment was moderate-quality for these outcomes.

Insulin versus diet

The evidence for perinatal mortality was inconclusive (RR 0.74, 95% CI 0.41 to 1.33; 4 RCTs, N = 1137; GRADE moderate-quality).

Insulin versus insulin

The evidence for insulin aspart versus lispro for risk of caesarean section was inconclusive (RR 1.00, 95% CI 0.91 to 1.09; 3 RCTs, N = 410; GRADE moderate quality).

No conclusions possible

No conclusions were possible for: lifestyle versus usual care (perineal trauma, postnatal depression, neonatal adiposity, number of antenatal visits/admissions); diet versus control (pre-eclampsia, caesarean section); myo-inositol versus placebo (hypoglycaemia); metformin versus glibenclamide (hypertensive disorders of pregnancy, pregnancy-induced hypertension, death or serious morbidity composite, insulin versus oral therapy (development of type 2 diabetes); intensive management versus routine care (IOL, large-for-gestational age); post- versus pre-prandial glucose monitoring (large-for-gestational age). The evidence ranged from moderate-, low- and very low-quality.

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