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