The complications in pregnancy due to measles can result in fetal losses and miscarriages and lower birth weight.
But Auckland Regional Public Health Service medical officer of health Dr William Rainger said while it could be "understandably concerning to pregnant mothers in Auckland", they should not be unduly concerned.
The likelihood of a pregnant woman being exposed to measles and catching it was no greater than any other person in the Auckland population and was a low risk.
Rainger said a person's immunity to rubella was tested as part of the routine antenatal care a pregnant woman received and if a person had been found to be immune to rubella then they would most likely be immune to measles because the immunisations were given together.
"Most people will be immune to measles," he said
However any pregnant women who were still concerned about their immunity status were advised to talk to their lead maternity carer provider and find out about their immune status in respect to rubella. They could also follow up with their GP and look at their Plunket records to potentially find out about their measles vaccination status and if there was still uncertainty have a blood test.
Meanwhile, Auckland Regional Public Health Service is cautiously optimistic that the number of measles cases in Auckland is on the decline.
So far this year there have been 1307 measles cases in Auckland and majority of those have been children aged under 5.
Rainger said fewer cases were presenting each week than when numbers peaked at the end of August.
Between 35 to 40 per cent of 1064 people with measles have been hospitalised during February to mid-September - much higher than previous outbreaks where only about 10 per cent of those who contract it ended up in hospital.
Of those hospitalised, 22 per cent of those resulted in complications such as pneumonia.
Bartholomew said just more than half of those admitted to hospital were children aged between 0 and 4. There was also a much higher number of Māori and Pacific Island people hospitalised than any other ethnicities.
Bartholomew said the main reasons for the higher hospitalisation rates were due to the larger number of children aged 0-4 years old having measles and because the latest data included anyone who had been in ED for longer than three hours.
Of those people who had measles, 42 per cent were Māori and 37 per cent were Pacific Islanders. The largest number of cases were in Counties Manukau.
Between January 1 and September 26 there have been 1498 confirmed cases of measles notified across New Zealand, according to the Ministry of Health, with 1246 cases occurring in Auckland.
