637 4060 ADDRESS: 60 Mount Street Lower, Grand Canal Dock, Dublin 2 info@merrionultrasound.ie

How babies experience fear is impacted by bacteria

According to a study conducted by Michigan State University and the University of North Carolina at Chapel Hill, the reason why some babies react more strongly to perceived danger lies in the infant’s digestive system.

We can find in the human digestive tract the intestinal microbiota which is a diverse bacterial community. According to the research team from Michigan State University and the University of North Carolina at Chapel Hill, the intestinal microbiota of newborns with high terror reactions and newborns with low or middle terror reactions differed.

These fear responses, or how a person reacts when confronted with a stressful situation, could be indicators of psychological health in the future. There is mounting evidence that intestinal microbiota is linked to neurological health.

The gut microbiota, according to this new study, may one day provide researchers and doctors with a new way to assess and promote healthy brain development.

Fear reactions in babies impacted by bacteria

How did the study about the fear reaction in babies go?

The study was done on animal first and after studying it in animals, Rebecca Knickmeyer, the study’s lead author and an associate professor in the Department of Pediatrics and Human Development at the College of Human Medicine, and her colleagues decided to investigate this relationship and its significance in the response to fear in humans. Understanding how people react to fear, particularly young children, may help predict mental health in some cases.

Reactions to fear are normal in a child’s development, according to the researchers. Children should be mindful of the potential threats in their surroundings and be prepared to respond. They are more likely to develop depression and anxiety later in life if they are unable to control their reaction while they are safe. Children with unusually attenuated fear responses may develop insensitive, emotionless traits in common with antisocial behaviour., according to Knickmeyer.

Knickmeyer and her colleagues conducted a pilot study with 30 newborns to see if the intestinal microbiota was associated with the response to fear in humans. The researchers chose the group with care to preserve as many elements that influence the intestinal microbiota as possible. For instance, all of the children were nursed and received no antibiotics.

The researchers then used stool samples to define the children’s microbiome, and a straightforward test to determine the child’s terror response: observe how a child reacted when a stranger entered the room wearing a Halloween mask

Study about fear reactions in babies

What are the results of this study about the fear reaction in babies?

After analysing all of the data, significant links have been discovered between specific aspects of the intestinal microbiota and the severity of newborns’ anxiety reactions.

Children with patchy microbiomes at one-month-old, for example, were more fearful by one-year-old. A small number of bacteria dominate unbalanced microbiomes, while balanced microbiomes have a more diverse bacterial community.

According to the results, the content of the microbial community around a year was also linked to the emotions of fear. Infants who reacted strongly had higher levels of some bacteria and lower levels of others than less fearful infants.

According to the researchers, there was no link between children’s gut microbiota and their reaction to unknown people who weren’t wearing masks. This is likely due to the different areas of the brain which is involved in dealing with potentially frightening events, according to Knickmeyer.

There is a social component to dealing with unknown people. Children may experience social phobias, but they do not perceive strangers as immediate threats. Children do not consider a mask to be social when they see one. It travels to a portion of the brain responsible for quickly assessing situations.

The researchers also used MRI technology to take images of children’s brains. After a year, they found that the content of the microbial community was related to the amygdala size, an area of the brain involved in making quick decisions in the face of potential danger.

To conclude, the microbiome can influence the development and function of the amygdala by connecting the research dots. This is just one of the many intriguing possibilities raised by the study, which the researchers is now replicating. Ms Knickmeyer is also eager to broaden her research horizons at IQ by forming new collaborations and posing new research questions. She mentioned that they have an excellent opportunity to support brain health early on and that their greatest challenge is to learn how to support development and healthy growth.



Nuchal Translucency

12-14 weeks


Anatomy Survey

21-22 weeks


Later Dating

10-17 weeks


Gender Scan

19 weeks onwards


Growth & Well Being

22 weeks onwards


Post Dates & Liquor

40 weeks onwards


What Our Patients Say

Gráinne Macken

This is my second visit to Merrion Fetal, I was very pleased on both occasions. Lovely quiet waiting room, appointment was on time. The 20-week scan is very detailed we enjoyed watching our baby on the large TV screen. We got some beautiful photos. The nurse was very pleasant and talked us through all the measurements and anatomy. I would highly recommend this scanning clinic.”

Áine Gibney

I had the best experience at the Merrion Fetal Health clinic for my 20-week big scan. The staff were so friendly and so nice and the lovely lady who did my ultrasound scan was amazing. She was so thoroughgoing to absolutely everything and gave me such reassurance on how my baby was growing and developing. I would recommend any Mother to be to attend here if you are looking for a comfortable, reassuring and super pleasant experience.”

Linda O'Sullivan

Highly recommend! We had an early scan due to a little scare at the start of pregnancy and then another at 12 weeks to make sure all was good again. Helen who was scanning on both days was fantastic. We felt totally relaxed and un-rushed while she took her time finding the best angle of baby to get us the clearest pictures as keepsakes all while making sure everything was perfect with baby. She reassured us throughout and I can honestly say it was the best money we ever spent getting both scans done.

Please let Helen know we are 18 weeks now and flying along Highly recommend!



About The Clinic

Merrion Fetal Health Pregnancy Scans Dublin 2

About The Consultants

Dr. Rhona Mahony

About The Team

Pregnancy scans lead sonographer at Merrion Fetal Health

Book Your Scan

Screen of Pregnancy Scan

Common Concerns

FAQs - Your Questions


GP Referral Scheme


Health Conditions


Healthy Pregnancy


Medical Studies


Patients' Information


Pregnancy Diary


Pregnancy Magazines

pregnancy health magazines

Scans & Services

18 weeks pregnancy scan facial profile Merrion Fetal Health

Susan's Trimesters

pregnancy trimesters

Videos By Consultants


Midwife sonographer facilitated

Consultant Led, Centre of Medical Excellence 


All articles on the blog and website are intended as information only. Please do not consider any of the information provided here as a substitute for medical advice. At all times seek medical advice directly with your own doctor and medical team.


This website was formerly Merrion Fetal Health. The clinic has undergone a rebrand and is now known as Merrion Ultrasound.