NHS England is urging mums-to-be in North Yorkshire and Humberside to get vaccinated against whooping cough.
Also known as pertussis, whooping cough is a highly-contagious bacterial infection of the lungs and airways which can cause severe illness.
Newborn babies are particularly at risk from whooping cough and are too young to be vaccinated themselves.
Women who have the vaccination provide some protection to their baby from birth as the vaccine passes on immunity from the mother to the unborn child.
Pregnant women should contact their GP after their 28th week of pregnancy to arrange for vaccination by the 38th week of pregnancy.
For further information see your midwife or GP or visit www.nhs.uk/vaccination.