A mother is calling for all pregnant women to be tested for strep after the infection left her baby with brain damage.
Bethany Ford tested positive for group B strep when she went into labour with her son Grayson Harris.
The 23-year-old had experienced a routine pregnancy and was not given antibiotics for the common bacterial infection.
By the time her results came back, she had already given birth to Grayson who was admitted to a special care baby unit with meningitis.
Now aged three, Grayson has global development delay which means he tends to be impulsive and can go from calm to angry very quickly.
He has difficulty processing things which has led him at times to self-harm through behaviour like pulling his own hair and he struggles with communication issues and unsettled sleep.
Bethany, from Mitcham in south west London, said: "The first few weeks of Grayson's life were incredibly traumatic and no parent should have to see their child suffer and struggle in the way he did.
"It is also difficult to take that following his birth it seemed like the doctors did not initially think there was any cause for concern."
Grayson was discharged from hospital two weeks after his birth in December 2015 but then readmitted several weeks later.
Following further tests, Bethany and her partner Keith Harris, 32, were told Grayson had a brain injury and now has global development delay.
Doctors confirmed his meningitis was caused by group B strep and Bethany is now campaigning for earlier testing in pregnant women.
The bacterial infection affects two in five people and, although normally harmless, it can prove problematic for pregnant women and their babies.
Bethany said: "The older Grayson gets the more we are noticing just how far behind other children his age he is.
"We love Grayson so much and are determined to ensure that he gets the best from life.
"However, we think it is also vital that steps are taken to ensure that group B Strep testing is undertaken a lot earlier than it was in our case.
"It's important to talk about this issue and we believe that something needs to change."
The couple are calling for all women to be tested on the NHS for group B strep between 35 and 37 weeks into their pregnancy so that appropriate care plans can be put in place to stop the infection being transmitted from mums to their babies.
They have instructed specialist medical negligence lawyers at Irwin Mitchell to investigate their son's care under Epsom and St Helier University Hospitals NHS Trust, which runs the hospital.
Richard Kayser, expert medical negligence lawyer at Irwin Mitchell said: "A simple test can be conducted to highlight whether an expectant mother is a carrier of the condition and her care plan can be adjusted to ensure intravenous antibiotics are provided throughout labour to prevent the infection being transmitted.
"Everything possible must be done to prevent this infection in babies."
Epsom hospital's Trust said it was unable to comment on this particular case.
Ramesh Ganapathy, clinical director of women and children's services, said: "In screening for the group B streptococcal bacteria, we follow current guidelines from the Royal College of Obstetricians and Gynaecologists.
"We fully recognise how serious and in some cases, devastating, it is when this bacteria spreads to a baby.
"As a result, we have agreed in principle to take part in a trial of universal screening for group B strep.
"We hope this trial will provide the evidence needed around universal screening, and we will implement any subsequent changes to the guidelines."