Maternal antibodies may protect babies from severe newborn infection caused by E. coli, after a study found the sickest infants had far lower levels.

A multi-centre study has shed new light on why some newborns become severely ill from Escherichia coli, or E. coli, while others do not.

The findings suggest most babies are protected by germ-fighting antibodies passed on by their mothers.

Sing Sing Way, an expert on immune system changes in expecting mothers and babies in the division of infectious diseases at Cincinnati Children’s and senior author on the study, said: “This helps explain a long-standing question: if most babies are exposed to germs soon after birth, why don’t even more develop severe infection?

“Our findings provide a key missing piece to this puzzle, the antibodies stimulated by the presence of these common bacteria in our intestines protect us against infection. 

“In pregnancy, the natural transfer of these germfighting antibodies from mothers to babies in the womb protect the vast majority against infection.

“In the rare situation when these antibodies are low in mothers or inefficiently transferred, babies are at much higher risk for infection.”

The study examined why only some babies develop severe infection from common bacteria.

E. coli is a common bacterium that lives in the intestines of nearly all people and is a leading cause of severe infection in newborn babies.

The research found that the babies who became most severely ill from E. coli infection also had markedly lower levels of germ-fighting antibodies transferred from their mothers.

The multi-centre research was led by Cincinnati Children’s, in collaboration with the University of Queensland in Australia, the University of Texas Southwestern Medical Center, Children’s Mercy Kansas City and the University of Missouri Kansas City School of Medicine.

To conduct the study, researchers retrieved dried blood samples collected during routine newborn screening from 100 babies who eventually developed E. coli infection and compared their antibody levels with those of hundreds of other infants who did not.

The analysis found that antibodies targeting E. coli were consistently reduced in infected babies. Because E. coli can vary widely, the researchers used a panel of strains isolated from infected babies to assess levels of these germ-fighting antibodies.

In a separate part of the study, the researchers used mice raised without any exposure to E. coli and therefore lacking the relevant antibodies.

They found that introducing a probiotic strain of E. coli, called Nissle 1917, to mice before pregnancy stimulated production of protective antibodies that efficiently protected newborn mice against infection.

The probiotic is widely available for human use in Europe, Asia and Australia under the trade name Mutaflor.

Mark Schembri, co-author and researcher at the Institute for Molecular Bioscience at the University of Queensland, said: “Understanding protection takes both types of evidence, what we can evaluate from specimens in human babies that naturally develop infection, and what we can test by experimentally causing infection.

“By strategically combining real-world human newborn screening samples with carefully designed infection models, we can start to pinpoint which antibody targets matter most and how broad protection might be achieved.”

Susana Chavez-Bueno, co-author from Children’s Mercy Hospital in Kansas City, said: “Neonatal sepsis can escalate quickly, and clinicians need better ways to identify which infants are at highest risk. These findings suggest a path toward earlier risk recognition and eventually, prevention strategies built around restoring the missing protective maternal antibodies.”

The researchers said they plan to develop a screening test to identify newborns at highest risk of severe E. coli infection, and eventually a probiotic that could be safe for mothers and strengthen their own immunity as well as the immunity transferred to their babies.

Pregnancy complications may leave women more vulnerable to the long-term heart effects of stress, a recent study suggests.

A study of more than 3,000 women in their first pregnancy found persistently higher stress levels were associated with higher blood pressure after pregnancy, specifically in women who had adverse pregnancy outcomes including preeclampsia, preterm birth, having a baby that was small for gestational age, meaning smaller than expected for that stage of pregnancy, or stillbirth.

Among women who experienced these complications, higher stress levels over time were associated with blood pressure that was 2 mm Hg higher than that of the low-stress group during the years two to seven after delivery.

This was not the case among women who did not experience adverse pregnancy outcomes.

Virginia Nuckols, lead author of the study and a postdoctoral fellow in the University of Delaware’s department of kinesiology and applied physiology, said: “For women who were having babies for the first time and had complications, referred to as adverse pregnancy outcomes, we found that higher stress levels over time were associated with higher blood pressure levels 2-to-7 years after delivery.

“This suggests that women who had pregnancy complications may be more susceptible to the negative effects of stress on their heart health, and taking steps to manage and reduce stress could be important for protecting long-term heart health.”

The researchers analysed records of 3,322 first-time mothers aged 15 to 44 who did not have high blood pressure before pregnancy.

The women were enrolled at 17 medical centres in eight US states, were pregnant with one baby and were having their first child. According to the authors, 66 per cent of participants self-identified as white, 14 per cent as Hispanic and 11 per cent as Black.

Blood pressure and stress levels were measured during the first and third trimesters, and again two to seven years after delivery.

Stress was assessed using the Perceived Stress Scale, a standard questionnaire that asks how often people feel situations are uncontrollable, unpredictable or overwhelming.

Those who experienced moderate to high stress levels were often younger, between 25 and 27 years of age, had higher body mass index, a measure based on height and weight, and lower educational attainment.

The authors said it is not yet clear exactly how higher stress leads to higher blood pressure in women who had pregnancy complications, and that several factors are likely to be involved.

Nuckols added: “Future studies should examine why women with a history of adverse pregnancy outcomes may be more susceptible to stress-driven increases in blood pressure and test whether stress reduction interventions can actually lower cardiovascular risk for these women.”

High blood pressure during pregnancy can have lasting effects on maternal health, including preeclampsia, eclampsia, stroke or kidney problems, according to the American Heart Association’s 2025 guideline for the prevention, detection, evaluation and management of high blood pressure in adults.

Monitoring blood pressure before, during and after pregnancy is crucial to help prevent and reduce the risk of long-term complications.

Laxmi Mehta is chair of the American Heart Association’s Council on Clinical Cardiology and director of preventive cardiology and women’s cardiovascular health at The Ohio State University Wexner Medical Center, and was not involved in the study.

Mehta said;’ “This study highlights the powerful connection between the mind and heart, emphasising the importance of stress management, particularly for those who have experienced adverse pregnancy outcomes.

“For the clinical care team, it reinforces the need to proactively assess and address stress as part of the comprehensive care we provide to our patients.

“Future research on whether targeted interventions to reduce or manage stress has a meaningful impact on long-term cardiovascular outcomes will be important as well.”

A second pregnancy alters the female brain in ways distinct from a first, according to research examining how motherhood affects brain structure and function.

The study tracked 110 women using repeated brain scans. Some became mothers for the first time, others had a second child, while a third group remained childless, allowing researchers to identify pregnancy-related brain changes.

During a first pregnancy, the greatest changes occurred in the default mode network, a brain system involved in self-reflection and social processes. During a second pregnancy, this network changed again, but less strongly.

Instead, a second pregnancy was associated with more changes in brain networks linked to directing attention and responding to stimuli, functions that may be useful when caring for more than one child.

Each pregnancy produced both shared and distinct effects on the brain, with patterns differing between first and second pregnancies.

Elseline Hoekzema, head of the Pregnancy Brain Lab at Amsterdam UMC, said: “With this, we have shown for the first time that the brain not only changes during the first pregnancy, but also during a second. During a first and second pregnancy, the brain changes in both similar and unique ways. Each pregnancy leaves a unique mark on the female brain.”

Milou Straathof, a researcher who analysed the data, said: “It appears that during a second pregnancy, the brain is more strongly altered in networks involved in reacting to sensory cues and in controlling your attention. These processes may be beneficial when caring for multiple children.”

The researchers also found a link between brain changes and the bond between mother and child, which was more pronounced during a first pregnancy than a second. They also observed associations between structural brain changes and peripartum depression, a form of depression that can occur during pregnancy or after birth, in both first and second pregnancies.

This provides the first evidence that changes in the cortex, the brain’s outer layer, during pregnancy are linked to maternal depression.

For women who became mothers for the first time, this link was especially visible after childbirth. For women having their second child, it was particularly apparent during pregnancy.

The researchers said: “This knowledge can help to better understand and recognise mental health problems in mothers. It is important that we understand how the brain adapts to motherhood.

They added that the findings could support better care for mothers, including the prevention and treatment of postnatal depression. Although most women experience pregnancy once or multiple times, scientists are only beginning to understand how it affects the brain.