Can infections in pregnancy lead to CHD? 

Yes, maternal infections during the first trimester are significantly associated with an increased risk of Congenital Heart Disease (CHD) in offspring. Clinical research indicates that any first trimester infection carries a pooled odds ratio of approximately 1.63 for developing heart defects. Pathogens such as the rubella virus, coxsackievirus, and influenza, along with associated high fevers, can disrupt the complex process of fetal organogenesis, leading to structural abnormalities like septal holes and outflow tract obstructions. 

Congenital Heart Disease (CHD) remains the most common type of birth defect, affecting roughly 8 to 9 in every 1,000 births in the UK. While genetic factors are a well known cause, the role of maternal environmental factors specifically infections has gained significant attention in recent clinical studies. The first trimester is the ‘critical window’ for heart development, where the heart transforms from a simple tube into a complex four chambered organ. This article reviews contemporary evidence regarding the impact of viral and bacterial infections on fetal heart health, providing an accurate overview of risks and preventative measures. 

What We will cover in this Article 

• Statistical prevalence of CHD linked to maternal infections 

• Specific pathogens associated with high cardiac risk, including Rubella and Influenza 

• The impact of maternal fever (hyperthermia) as a developmental trigger 

• Emerging 2025 data on the link between SARS-CoV-2 and heart defects 

• Biological mechanisms of how pathogens cross the placental barrier 

• NHS safety and prevention guidance for expectant mothers 

The Link Between Maternal Infections and CHD 

Maternal infections during the first trimester increase the risk of CHD by approximately 63% on average. Pathogens or the resulting inflammatory response can interfere with the proliferation and migration of fetal cardiac progenitor cells, which are essential for building the heart’s chambers. Recent meta-analyses involving over 1.7 million pregnancies have confirmed that first trimester maternal infections carry a pooled odds ratio of 1.63. According to the European Heart Journal, Guo, H., et al. (2025). ‘First trimester maternal infections and offspring congenital heart defects: a meta-analysis.’  these associations appear to vary by type of infection and extend beyond infections commonly tested for during routine pregnancy screening. 

The heart begins to form as early as three weeks after conception, and by week eight, the basic structure is complete. Any disruption during this time can result in permanent structural anomalies. Statistical evidence shows that ventricular septal defects (VSD) and atrioventricular septal defects (AVSD) are the most frequent structural outcomes of these exposures. This risk underscores the importance of general infection prevention during the early stages of gestation. 

Specific Viral and Bacterial Triggers 

Specific pathogens vary in their level of risk, with the rubella virus showing the highest overall association with heart defects. Other viruses such as coxsackievirus and influenza also significantly raise the probability of cardiac malformations. Furthermore, 2025 clinical data has identified a specific link between SARS-CoV-2 infection during gestational weeks 4 to 6 and a significant increase in certain cardiac anomalies and situs inversus. 

The following table summarizes clinical data on specific infection types and their associated odds ratios for CHD: 

Pathogen/Infection Type	Odds Ratio	Associated Heart Defect
Rubella Virus	2.78	PDA, Pulmonary Stenosis
Coxsackievirus	1.57	Valve defects, Myocarditis
Influenza (with fever)	1.50	Outflow tract obstruction
Respiratory Infections	1.57	Septal defects (VSD, ASD)
SARS-CoV-2 (Weeks 4-6)	6.54	Situs inversus, Cardiac anomalies

Research suggests that these pathogens can induce placental inflammation, which impairs the exchange of nutrients and oxygen, potentially leading to fetal hypoxia and disrupted signaling during the period of cardiac septation. 

The Role of Maternal Fever (Hyperthermia) 

Maternal fever is a potent trigger for CHD, independent of the underlying infection. A core body temperature above 38°C during the first trimester is considered teratogenic, meaning it can directly cause birth defects by disrupting the folding of proteins essential for heart tissue growth. Clinical data yields a pooled odds ratio of 1.53 for maternal fever in the first trimester. 

Fever specifically interferes with the migration of neural crest cells, which are vital for forming the heart’s plumbing, such as the aorta and pulmonary artery. This is why febrile illnesses are most closely linked to conotruncal defects, such as Tetralogy of Fallot. Timely management of fevers with pregnancy safe medications like paracetamol is a standard clinical recommendation within the NHS to mitigate these developmental risks. 

Differentiation: Infection vs. Genetic Factors 

It is important to differentiate between CHD caused by environmental triggers like infection and those with a purely genetic basis. While chromosomal abnormalities like Down’s syndrome are detected in 8% to 12% of cases, environmental factors are often ‘modifiable’ risks. If an infection occurs in a genetically typical fetus, the resulting heart defect is a direct consequence of the environmental disruption rather than an inherited trait. 

In some instances, an infection can ‘unmask’ an underlying genetic susceptibility. This means a baby might have a minor genetic variation that would not normally cause a problem, but when combined with the stress of a maternal infection or fever, a structural heart defect manifests. Understanding this difference helps medical teams determine the likelihood of recurrence in future pregnancies. 

To Summarise 

Maternal infections and high fevers during the first trimester are proven risk factors for Congenital Heart Disease. Clinical data from 2024 and 2025 emphasizes that pathogens like Rubella, Influenza, and SARS-CoV-2 can significantly increase the odds of structural heart defects. While the absolute risk for most individual infections remains low, early vaccination and the prompt management of fevers are essential components of safe prenatal care to protect the developing fetal heart. 

If you experience a high temperature, a new rash, or symptoms of a viral infection while pregnant, contact your midwife or GP for advice. 

If you experience severe, sudden, or worsening symptoms, such as difficulty breathing or a high fever that does not respond to paracetamol, call 999 immediately. 

Authority Snapshot (E-E-A-T Block) 

This article was reviewed by Dr. Stefan Petrov, a UK-trained physician (MBBS) with postgraduate certifications in ACLS and BLS. Dr. Petrov has extensive clinical experience in general medicine and emergency care, having worked in hospital wards and intensive care units. His expertise in medical education ensures this information aligns with the latest 2025 clinical meta-analyses and NHS safety standards.