Oxfordshire MP Freddie van Mierlo accompanied constituent Leona Hayes to Number 10, where she presented a petition seeking routine Group B Streptococcus screening for every pregnant woman.
The campaign wants the Government to introduce testing between 35 and 37 weeks of pregnancy, ensure the service is available throughout the NHS, and provide antibiotics during labour to women who test positive.
Hayes began the campaign after finding during her own pregnancy that she carried GBS.
According to the campaign, approximately one in four pregnant women in the UK carry the bacteria, frequently without being aware of it.
GBS can lead to serious infections among newborn babies, including sepsis, pneumonia and meningitis.
Routine screening of the population is not presently recommended by the UK National Screening Committee, leading some women to fund private tests.
Hayes said leaving newborn health to chance was unacceptable.
She said GBS was harmless to adults but was the leading cause of severe infections in newborns, including sepsis, pneumonia and meningitis.
She added that the condition claims the lives of four babies each month and causes severe, permanent disabilities in four surviving babies each month.
Families affected by the infection had told Hayes of the devastation experienced, she said.
She argued that access to potentially life-saving screening was unjust because the tests were available only through private payment or specific NHS clinical eligibility.
Hayes said screening and antibiotics administered during labour could prevent as many as 90 per cent of early-onset GBS cases.
She maintained that a mandatory offer of testing could save newborn lives, reduce the trauma experienced by families and prevent avoidable losses.
Van Mierlo described the absence of routinely available screening for pregnant women as shocking.
He said infections caused by Group B Strep are often preventable and that making testing routinely accessible would save lives and reduce the risk of lifelong disability.
The MP also said mothers and babies should have equal access to care.
Under the current arrangements, he said, screening is restricted to women able to pay privately or those who meet specific clinical criteria within the NHS.
Babies, he argued, should not face the risk of a preventable infection because their mothers fall outside either category.
Van Mierlo criticised the UK National Screening Committee as no longer fit for purpose.
He accompanied Hayes because he believed the Government needed to give greater attention to the issue.
The petition remains open until 3 December and asks ministers to require that GBS screening be offered to all pregnant women.
It is listed on the UK Parliament petitions website.