Maternal diabetes can be a cause of congenital malformations and death in infants. Diabetic mothers planning pregnancy need to be able to minimise these risks through good information, advice and care. What forms of care are most effective?
This systematic review set out to examine the evidence on giving specific pre-pregnancy care (PPC) in preventing malformations and improving maternal outcomes.
In women with diabetes mellitus intending to get pregnant, does pre-pregnancy care incorporating diabetes-specific education and medication management reduce the risks of congenital malformation or maternal death?
The reviewers searched key databases for clinical trials and observational studies that examined the question. Three independent reviewers examined the results and compiled a list of papers for inclusion.
A range of very different intervention types was covered. These included tight blood glucose control, SMBG, counselling, education, screening, folic acid supplementation and the use of contraception until optimal glycemic control is achieved.
Data from these studies were pooled to find an overall estimate of the impact of PPC on HbA1c, hypoglycaemia, congenital malformations and perinatal mortality.
21 studies were found, of which:
- one was a controlled trial
- 13 were prospective cohort studies
- 6 were retrospective cohort studies
- one was a case-control study.
The pooled analysis found that pre-pregnancy care substantially reduced the risk of congenital malformations (Relative Risk 0.25, 95% CI 0.16-0.37) and perinatal mortality (RR 0.34, 95% CI 0.15-0.75.
There was no evidence of statistical heterogeneity between the studies for these outcomes.
PPC was found to lower HbA1c by an average of 1.92% in the first trimester, but there was a lot of heterogeneity around this outcome.
- This was a comprehensive, rigorous systematic review.
- The reviewers probably found all of the important evidence and used appropriate methods to ensure that their analysis was fair.
- The search was undertaken in December 2011, so important studies may have been published since.
- All of the studies they included were non-randomised studies, which we must consider as being at risk of bias in the context of questions of prevention.
- Congenital malformations and perinatal mortality are, thankfully, rare outcomes. This means that randomised trials can be impractical. There may also be ethical issues in withholding pre-pregnancy care from a control group. Observation studies, particularly prospective cohort studies, offer the best bet for good quality evidence in this area.
- The reviewers appraised the quality of the studies and provided a detailed assessment of the risk of bias in each.
- Many of the observational studies were poor quality. The reviewers were careful to exclude these studies from their meta-analysis.
- The consistency and strength of the findings of the individual studies and meta-analysis strongly suggests that pre-pregnancy care has substantial benefits for both mother and baby.
- Although the studies all evaluated slightly different interventions, there appears to be sufficient similarities between them to warrant meta-analysis.
- The review did not provide any information about the comparison intervention. This might be important in evaluating what benefits might be expected in a given clinical setting.
- The reviewers cite studies which show that only 34-38% of eligible women actually receive pre-pregnancy care. The focus should be on increasing uptake of these types of programme.
- There was some evidence of cost savings as a result of pre-pregnancy care.
- There was also some evidence of an increased risk of hypoglycaemia during the first trimester amongst women who had the pre-pregnancy care.
Wahabi HA, Alzeidan RA, Esmaeil SA. Pre-pregnancy care for women with pre-gestational diabetes mellitus: a systematic review and meta-analysis. BMC Public Health. 2012 Sep 17;12:792. doi: 10.1186/1471-2458-12-792.