Charity-funded research shows link between blood type and premature birth risk
Charity-funded research shows link between blood type and premature birth risk
10 September 2025
The findings, published today (10th September) in npj Biofilms and Microbiomes, looked at more than 74,000 anonymised maternity records from Imperial College Healthcare NHS Trust and data from high-risk pregnancies. The team found that women with blood groups B and O were associated with a higher risk of spontaneous preterm birth, while those from blood group A were associated with a lower risk.
The clinical researchers believe this is because women with blood group A are more likely to carry higher proportions of a protective bacterium and show less inflammation, both associated with healthy pregnancies.
They found that women with blood group A were more likely to carry more of the 'good bacterium' Lactobacillus crispatus – associated with healthy pregnancies. In contrast, women of blood group B and O were more likely to have a more wider mix of bacteria. In women with blood group O, the researchers observed a direct link this mix of bacteria, inflammation, and spontaneous preterm birth.
Dr Lynne Sykes, lead researcher and Clinical Associate Professor at Imperial College London, and Consultant Obstetrician at Imperial College Healthcare NHS Trust, said:
“Although we did not establish causation, we have identified a genetic link that can influence the risk of spontaneous premature birth in women. This could potentially impact women in the future by identifying risk earlier in pregnancy and by offering more tailored interventions. While we need further research, the prospect of moving towards personalised care in this area is hugely exciting.”
The research suggests that the ABO blood group – which is routinely tested early in pregnancy – could be used to help doctors identify women at risk of preterm birth, especially when considered alongside other clinical factors.
Dr Sykes added:
“What excites me most is the opportunity this presents for truly personalised medicine in pregnancy – something that has been sorely lacking in our field. The treatments we currently offer to prevent preterm birth have barely changed in decades. This research opens the door to more targeted, biologically-informed interventions.”
The study was co-funded by Imperial Health Charity through its partnership with The Parasol Foundation.
Ms Ruth Monicka Parasol, Principal Benefactress of The Parasol Foundation, which co-funded this research, said:
“Investing in women’s health research is vital — not only to close long-standing gaps in scientific understanding, but to improve care and outcomes for women and babies around the world. We are incredibly proud to support this important work and to be part of advancing knowledge that could transform the way we manage pregnancy risks for generations to come.”
The study also lays the groundwork for new therapeutic approaches. A clinical trial beginning this autumn will explore whether probiotic treatment with Lactobacillus crispatus can help reduce premature birth in high-risk women – and whether response to the treatment may vary by blood group.
You can find out more about the work made possible by our partnership with The Parasol Foundation here.
