One in 15 babies in Dacorum are born underweight, new figures show.
The Royal College of Paediatrics and Child Health says underweight babies are more likely to develop some health conditions, such as heart disease or diabetes, in adulthood.
ONS data reveals that, in Dacorum, 135 newborns weighed under 5.5 lbs, considered the minimum healthy weight, in 2017.
That's 6.9% of the births in Dacorum over the year.
The NHS says maternity services can identify mothers at risk of having underweight babies, and refer them for help and support.
Gergely Toldi, from the Royal College of Paediatrics and Child Health, said low birth weight can be caused by numerous factors.
"Prematurity is often associated with a low birth weight because the baby had less time to grow in the womb", he said.
"However, babies born at term can also be small due to either a disease in the baby or a problem with the placenta, leading to insufficient nutrient and oxygen supply.
"Babies born with a low birth weight have an increased risk for developing certain diseases in adulthood, such as heart disease, chronic kidney disease and diabetes."
Mothers suffering from high blood pressure, or smoking or drinking alcohol during pregnancy, are more likely to have babies weighing 5.5 lbs.
Across England and Wales, 7% of babies were underweight at birth in 2017, 47,228 in total.
That is a drop of 3% compared with the number in 2016.
In Walsall, in the West Midlands, 11.2% of babies were underweight, the highest rate in England and Wales. The Vale of White Horse, in South East England, registered the lowest, with only 3.6% of babies under 5.5 lbs.
An NHS spokesman said: "Effective maternity services commissioned by Clinical Commissioning Groups can identify and address such issues within pregnancy either directly or by referral.
"Even where the relevant service is not commissioned by a CCG, for example, smoking cessation, the identification and referral of women with a need for such support falls within the role of maternity services.
"If the number of full-term live births with a low birth weight within an area is disproportionately high, CCGs should consider the reasons for this and what actions they should take to address it."
In Dacorum, there were 1,951 births in 2017 - 1,052 boys and 899 girls.
There were 68 newborns for every 1,000 women aged 15 to 44 in the area, compared with an average of 61 in England and Wales.