# Pre‐Existing and Gestational Diabetes and Risk of Maternal Venous Thromboembolism: A Systematic Review and Meta‐Analysis of Observational Studies

## TL;DR

This study finds that gestational diabetes increases the risk of blood clots during pregnancy, but not after childbirth, while pre-existing diabetes shows no clear link.

## Contribution

The study provides a meta-analysis of observational data to clarify the relationship between diabetes types and maternal venous thromboembolism risk.

## Key findings

- Gestational diabetes is associated with a 2.48-fold increased risk of antepartum VTE.
- Pre-existing diabetes does not show a significant association with antepartum VTE.
- Neither diabetes type shows a clear link to postpartum VTE.

## Abstract

Women who are pregnant are at increased risk of venous thromboembolism (VTE), which persists for up to 3 months following childbirth. Diabetes is known to increase the risk of serious cardiovascular outcomes.

To comprehensively review literature on the extent to which pre‐existing or gestational diabetes influences the risk of VTE in both pregnancy and postpartum.

We used Medline, Embase and Google Scholar to identify observational studies published up to 2 November 2023.

Studies which quantified the relationship between diabetes on antepartum and/or postpartum VTE, and which provide separate data for pre‐existing and gestational diabetes.

Results were pooled, where appropriate, using random‐effects meta‐analysis.

Twenty one studies from Europe, the United States and Asia were included. There was an increased risk of antepartum VTE in women with gestational diabetes (RR = 2.48, 95% CI 1.47 – 4.16, I
2= 45%, 4 studies) but not pre‐existing diabetes (RR = 1.71, 0.43 – 6.77, I
2= 68%, 2 studies). For postpartum VTE, there was no clear association with either pre‐existing (RR = 1.28, 0.73 – 2.24, I
2= 73%, 6 studies) or gestational (RR = 1.39, 0.77 – 2.51, I
2= 70%, 10 studies) diabetes.

Our results will provide some reassurance for pregnant women with pre‐existing or gestational diabetes, owing to no clear evidence of an increased risk of maternal VTE. While some studies report a raised risk of VTE during antepartum specifically, results must be interpreted in light of high levels of heterogeneity.

Linked article: This article is commented on by van der Slink pp. 1086 in this issue. To view this article visit https://doi.org/10.1111/1471-0528.18138.