Northland Health is urging pregnant women to protect themselves against whooping cough by vaccination.
The upper North Island region has had 93 cases of the disease notified this year - more than the total number for the whole of 2012.
Northland Medical Officer of Health Claire Mills says whooping cough poses serious risks to newborn babies and young infants, with three in every four infected are ending up in hospital.
She says women between 28 and 38 weeks of pregnancy should ask for their free vaccination to boost their babies' antibodies till they can be vaccinated themselves at six weeks.
Dr Mills says the chances of catching whooping cough in Northland this winter are high.
Many people are not diagnosed, and for every case notified there are probably 80 to 100 more in the community, she says.