Probiotics to prevent gestational diabetes mellitus

Gestational diabetes mellitus is a condition where the mother has high blood sugar levels during pregnancy. It is associated with a range of adverse pregnancy outcomes for the mother, such as pre-eclampsia (high blood pressure with protein in the urine) and instrumental or operative delivery, as well as for the infants who may be born large-for-gestational age. Current treatment includes diet with or without medication. Prevention of this condition would be preferable to treatment. Preventative diet and lifestyle interventions are time consuming and do not always reduce the number of women getting gestational diabetes. Probiotics - 'good' bacteria that are usually taken in the form of capsules or drinks - supplement the gut bacteria. They have the potential to change a person's metabolism and so prevent gestational diabetes mellitus. This review was designed to look at whether there is evidence to show if this is true or not. At the moment there is only one randomised controlled study, which involved 256 women. This study does show a lower rate of gestational diabetes mellitus in women who took probiotics from early pregnancy, with the rate of diagnosis of gestational diabetes mellitus being reduced by two-thirds and their babies on average weighed 127 g less at birth. This study did not find differences in the rates of miscarriage, intrauterine or neonatal death or stillbirth. There was no clear evidence of a change in the proportion of women delivered by caesarean section or in the risk of preterm delivery. The study did not report on how much weight the mothers gained during pregnancy or how many babies were large-for-gestational age or that weighed more than 4000 g at birth or on the body composition of the babies. One study is not enough to draw any definite conclusions at the moment. There are other studies underway.

Authors' conclusions: 

One trial has shown a reduction in the rate of GDM when women are randomised to probiotics early in pregnancy but more uncertain evidence of any effect on miscarriage/IUFD/stillbirth/neonatal death. There are no data on macrosomia. At this time, there are insufficient studies to perform a quantitative meta-analysis. Further results are awaited from four ongoing studies.

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Background: 

Gestational diabetes mellitus (GDM) is associated with a range of adverse pregnancy outcomes for mother and infant. The prevention of GDM using lifestyle interventions has proven difficult. The gut microbiome (the composite of bacteria present in the intestines) influences host inflammatory pathways, glucose and lipid metabolism and, in other settings, alteration of the gut microbiome has been shown to impact on these host responses. Probiotics are one way of altering the gut microbiome but little is known about their use in influencing the metabolic environment of pregnancy.

Objectives: 

To assess the effects of probiotic supplementation when compared with other methods for the prevention of GDM.

Search strategy: 

We searched the Cochrane Pregnancy and childbirth Group's Trials Register (31 August 2013) and reference lists of the articles of retrieved studies.

Selection criteria: 

Randomised and cluster-randomised trials comparing the use of probiotic supplementation with other methods for the prevention of the development of GDM. Cluster-randomised trials were eligible for inclusion but none were identified. Quasi-randomised and cross-over design studies are not eligible for inclusion in this review. Studies presented only as abstracts with no subsequent full report of study results would also have been excluded.

Data collection and analysis: 

Two review authors independently assessed study eligibility, extracted data and assessed risk of bias of included study. Data were checked for accuracy.

Main results: 

Eleven reports (relating to five possible trials) were found. We included one study (six trial reports) involving 256 women. Four other studies are ongoing.

The included trial consisted of three treatment arms: probiotic with dietary intervention, placebo and dietary intervention, and dietary intervention alone; it was at a low risk of bias. The study reported primary outcomes of a reduction in the rate of gestational diabetes mellitus (risk ratio (RR) 0.38, 95% confidence interval (CI) 0.20 to 0.70), with no statistical difference in the rates of miscarriage/intrauterine fetal death (IUFD)/stillbirth/neonatal death (RR 2.00, 95% CI 0.35 to 11.35). Secondary outcomes reported were a reduction in infant birthweight (mean difference (MD) -127.71 g, 95% CI -251.37 to -4.06) in the probiotic group and no clear evidence of increased risk of preterm delivery (RR 3.27, 95% CI 0.44 to 24.43), or caesarean section rate (RR 1.23, 95% CI 0.65 to 2.32). The primary infant outcomes of rates of macrosomia and large-for-gestational age infants were not reported. The following secondary outcomes were not reported: maternal gestational weight gain, pre-eclampsia, and the long-term diagnosis of diabetes mellitus; infant body composition, shoulder dystocia, admission to neonatal intensive care, jaundice, hypoglycaemia and long-term rates of obesity and diabetes mellitus.

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