Midwives have appealed to the Government to urgently deal with a "crisis" in their sector, as they say pregnant women are struggling to get maternity care.
Auckland, Tauranga, Canterbury and parts of the Waikato are among the areas understood to be suffering from the shortage.
Immigration New Zealand added midwives to the "immediate skill shortage" list in December.
The New Zealand College of Midwives is blaming years of underfunding of the service, with midwives' pay failing to keep pace with inflation.
Canterbury DHB experienced a particularly bad shortage of midwives in December, with more than 140 women unable to find a midwife to act as their Lead Maternity Carer over the Christmas period.
The latest DHB board meeting agenda noted that the local Midwife Resource Centre allocated midwives to more than half the women, with on-call midwives caring for 50 who could not get continuous care from one midwife.
• Waikato women struggling to find midwives as they leave the profession in droves
• Govt monitoring the midwife crisis in Wanaka
• New South Auckland birthing centre will help with 'dire shortage' of postnatal beds
Most DHBs were unable to provide figures on midwife shortages at short notice.
The New Zealand College of Midwives said it had warned the previous Government over many years that pay for community midwives was failing to keep pace with inflation and the level of work required of midwives.
Understaffing was undermining morale in hospitals and maternity units, it said.
"We are hearing an increasing number of stories from around the country of severe shortages as midwives continue to leave the profession," chief executive Karen Guilliland said. "We can now see a pattern confirming that this is a service in crisis."
The College's midwifery advisor Alison Eddy said that Auckland DHB also had a "longstanding issue" with recruiting midwives.
"There's been a lot of work going on in the DHB at an operational level to try and address the recruitment and retention issues," she said.
"This is a national issue - there are simply not enough midwives. But this issue seems to be particularly acute for the Auckland DHB and their tertiary hospital."
The College was getting an increasing number of queries from midwives raising concerns about working conditions, Eddy said.
"There simply aren't enough midwives, and they're feeling increasingly stressed and stretched, upset and frustrated that they can't give the care that they want to."
These concerns had been escalated to a board member at Auckland DHB, she said.
A spokeswoman for Auckland DHB said they had been affected by the shortage.
"We have been working with our union partners and midwifery organisations to provide additional support for our staff. Our aim is to work closely alongside the New Zealand College of Midwives to ensure that midwifery remains an attractive and evolving profession and to help them increase trained midwife numbers in New Zealand."
She said they had 146 midwives and had filled many vacancies recently.
"In the past three months we have had 10 new midwives start with us. We also have six experienced midwives at various stages of the recruitment process, and 35 applicants for our graduate midwifery programme (May 2018 intake).
"We are in the process of recruiting to 17 new, additional positions that have been established to further support increasing demand.
"The public can be reassured that Auckland DHB has a skilled, dedicated staff who provide an excellent standard of care for mothers, babies and their families. Feedback from our patients is welcomed and helps us improve our service."
The College of Midwives began fighting for pay equity across the country three years ago when it began court action under the previous Government.
Last year the College and the Ministry of Health reached an agreement to design a new funding model for community-based (LMC) midwives.
That process has been worked on since May 2017, ministry director of service commissioning Jill Lane said.
"The Ministry of Health is committed to providing high quality maternal and child health services in New Zealand," she said, adding that New Zealand's service quality was high by international standards.
"Any funding decision is part of the Budget process and confidential. The Ministry is working with district health boards to address the workforce pressures in some areas of the country."
The Budget will be delivered on May 17.