New Zealand babies are dying from syphilis passed on from their mothers during pregnancy.

The stillbirths are the "train wreck" doctors have long warned of, as sexually transmitted infections boom amidst claims of underfunded health services.

All women should be screened for syphilis early in pregnancy. However, the Herald has confirmed cases - including a stillbirth - where that crucial testing wasn't done.

There have been four cases of congenital (mother-to-baby) syphilis since 2017, and one probable case. The Ministry of Health, which has set up a group to fight the spread of the infection, is currently following up a further two possible cases.

Of the cases last year, two were stillbirths.

Women should have antenatal blood tests at the first contact with a health professional during pregnancy. If detected, syphilis is easily cleared with antibiotics.

Dr Jane Morgan, clinical director of Waikato DHB's Hamilton Sexual Health, told the Heraldconfirmation of congenital syphilis in New Zealand was "completely appalling".

"The WHO [World Health Organisation] has given Cuba an award for eliminating congenital syphilis. We are reintroducing it," said Morgan, also an honorary academic at the University of Auckland.

"[It] basically says, 'our health care systems are falling over.' I'm reeling a bit. It's just heartbreaking that we are seeing it. It is hard to comprehend.

"We know that LMCs [lead maternity carers] are talking about how short staffed they are, and that midwives are leaving that profession. What is happening about people's access to primary care...why aren't women being screened?"

Hospital workers occasionally help women give birth who have had no prior antenatal care. Northland DHB's hospital advisory committee noted last month that three women had presented in labour "unbooked" and with no antenatal care, and this seemed to be more common.

However, there have also been oversights when women are in contact with the health system.

A presentation at a health forum earlier this year by Tauranga-based sexual health clinician Dr Massimo Giola included summaries provided by different regions.

Five pregnant women in Auckland have been treated for syphilis this year. One woman delivered a baby with untreated syphilis. "She tested [positive] during antenatal screening but was not informed or treated prior to delivery. Fortunately the baby is OK," say the presentation notes, provided to the Herald.

Tauranga and Whakatane Sexual Health Service reported a congenital syphilis stillbirth. The mother was seen by a midwife and GP during pregnancy and had genital ulcers but didn't have antenatal testing, the notes state. Syphilis is more common among gay men but there seemed to be a lack of knowledge among GPs and midwives about how widespread it was becoming in the heterosexual community.

Giola outlined resourcing problems. There are just 2.1 full time equivalent sexual health physicians for the entire Auckland region. Public health units don't have resources to track difficult-to-find women and clinics were cancelled at one unnamed DHB with patients turned away.

"The current outbreak of heterosexual syphilis and cases of congenital syphilis are the demonstration of the blatant failure of 10 years of policies of devolution of sexual health to primary care without support and training of the primary care workforce," Giola wrote.

"The network of sexual health clinics, which were the safety net when primary care could not cope, is falling apart due to job cuts and a lack of strategic direction."

Giola recommended making ongoing sexual health training for GPs mandatory, along with real-time reporting of STI data and accountable targets for DHBs.

A Ministry spokesman confirmed that since 2017 there had been three live births where the infant had congenital syphilis and those babies had received follow-up treatment.

Sexual health clinics, midwives and general practitioners had been told of the increased prevalence of syphilis "and the need for vigilance in their communities", the spokesman said.

The Ministry has records of one stillbirth with congenital syphilis in 2016, and one in 2011-2012. Records couldn't be checked prior to 2011.

There were about 495 confirmed cases of syphilis last year - over double the number in 2015. Almost 70 per cent of cases were in men who have sex with men.

Swipe for syphilis?

Smartphone apps like Tinder and Grindr should be made to tell users about sexually-transmitted infections, a physician says.

Canterbury DHB sexual health centre physician Dr Heather Young has long warned about the potential "train wreck" of mother-to-child syphilis cases. Now congenital syphilis cases are happening, she said action was needed.

Most importantly, Young said more ring-fenced funding was needed for specialist sexual health clinics and workforces. GPs should have core sexual and reproductive health competencies in order to claim for free consultations.

She also believes dating apps like Tinder should play their part. Under NZ law industries making financial gain from sex are obliged to act safely. Young said in her view that should require apps like Tinder to display public health messages about STIs.

"Currently these platforms either request payment to advertise or decline putting such ads on their sites."