Alarm over revelations that a number of babies in this country are dying after contracting syphilis from their mothers.

Hamilton Sexual Health's clinical director, Dr Jane Morgan, says syphilis should be easily picked up and treated when expectant mothers are blood tested during pregnancy.

She says the World Health Organisation calls one case of congenital syphilis, a system failure.

New Zealand had four last year, and two resulted in stillbirths.

Morgan told Mike Hosking there's been a resurgence in the infection.

"I don't think that people realise there has been such a marked increase in recent years. We've gone from having maybe 30 or 40 in New Zealand a year to having nearly 500 last year."

LISTEN TO JANE MORGAN TALK WITH MIKE HOSKING ABOVE