Newman, C. & Dunne, F. P. | 2021| Metformin for pregnancy and beyond: the pros and cons | Diabetic Medicine | https://doi.org/10.1111/dme.14700
The authors of this review set out to review the benefits and potential pitfalls of metformin use in pregnancy. To this end they conducted a literature search of web-based databases (including PubMed, CENTRAL via the Cochrane Library and EMBASE) using identified search terms. They read the full texts of any relevant texts published in English and searched clinicaltrials.gov for relevant unpublished trials. The team included randomised controlled trials (RCTs), cluster RCTs, pilot and feasibility studies in our review. They excluded conference abstracts, case reports and case series. Observational data which were deemed to be of high quality were also considered. Additionally, the researchers searched bibliographies for all relevant publications to identify other studies.
In this paper they report their findings that metformin has many maternal advantages when taken during and after pregnancy, including reduced maternal GWG, PTD and insulin requirements, a reduction in operative delivery and possible reduction in hypertensive disorders and future type 2 diabetes. Some benefits are even greater for women with a BMI more than or equal to 30 kg/m2 (Source: Newman & Dunne, 2021).
Context and Aim
Metformin has been used in pregnancy since the 1970s. It is cheap, widely available and is acceptable to women. Despite its increasing use, controversy remains surrounding its benefits and risks. Metformin effectively reduces hyperglycaemia for the mother during pregnancy and it reduces rates of macrosomia and neonatal hypoglycaemia. However, concern exists surrounding an increase in the rate of SGA births and obesity in childhood. We aim to review the evidence and expert opinion behind metformin in pregnancy through to the post-partum period.
We performed a literature review of relevant studies from online databases using a combination of keywords. We also searched the references of retrieved articles for pertinent studies.
There is strong evidence that metformin is safe in early pregnancy with no risk of congenital malformations. If used throughout pregnancy, it is likely to lead to reduced maternal weight gain and reduced insulin dose in women with type 2 diabetes. In infants, metformin reduces hypoglycaemia and macrosomia but may increase the rate of infants born SGA. There is some evidence of an increased risk of obesity and altered fat distribution in offspring. Metformin appears well tolerated in pregnancy and is more acceptable to women than insulin therapy.
Due to increasing rates of maternal obesity, GDM and type 2 diabetes, metformin use in pregnancy is increasing. Overall, it appears safe and effective but further research is needed to examine mechanisms linking metformin to obesity reported during childhood in some follow-up studies.
- Metformin has been used outside of pregnancy for decades and has multiple benefits in pregnancy including reduced weight gain and a potential decrease in pre-eclampsia (PET).
- However, some clinicians have concerns regarding its use due to increased rates of small for gestational age (SGA) births and adiposity in infants exposed to metformin.
- With the rising rates of obesity and gestational diabetes (GDM), cheap, acceptable and effective treatments for hyperglycaemia are needed.
- This study follows the use of metformin from the pre-conception to the post-partum period and examines the evidence for and against its use.
The primary paper is available from the journal Diabetic Medicine