They might be visiting clinics; they could be going to their GPs. They're possibly being checked out by an obstetrician - and some may not be getting any care.
But no-one really knows how 11.2 percent of New Zealand's pregnant women are being cared for.
That statistic is revealed in the Ministry of Health's Report on Maternity.
The lack of concrete information has alarmed Wellington family doctor and University of Otago lecturer Ben Gray.
"These babies are not getting a fair go. We're condemning a group of babies - the size of which we do not know - to inadequate care during the time when they have the least ability to do anything about it, while they're in their mother's womb, and these can have long-term consequences for their lives".
The ministry's figures do show that almost 90 percent of women are looked after by what's known as a lead maternity carer, who is usually a community midwive.
So, while those women are receiving the attention they need, Dr Gray said the others could be missing out on crucial examinations.
"If a woman does not receive antenatal care it means that her delivery is going to be at greater risk. There may be some undiagnosed issues that are there," he said.
"It also means that our opportunity to have given this baby a really good start in life has been missed and can have major consequences.
"For example, with fetal alcohol syndrome... if a woman doesn't get any antenatal care, we haven't had an opportunity to influence the outcome."
Poor data reporting could be factor
Social services provider Pregnancy Help has noticed a trend of women not signing up with a midwife, national president Diane Thornton said.
"Anecdotally, some of our branches are reporting seeing more women who have not engaged with antenatal care and who have not registered with a lead maternity carer.
'They're missing out on ongoing monitoring of their own health and perhaps picking up of complications at an early stage. The babies are missing out on monitoring so that development can be monitored and watched."
The College of Midwives, which is the professional organisation for midwives, said poor data reporting from district health boards (DHBs) could be a factor.
A spokesperson, Alison Eddy, agreed with the ministry's hunch that hospitals are taking care of women who are not with a community midwife.
"We are aware that there are a very small number of women who don't seek maternity care. But from what we understand it's a lot less than the 11 percent reported," she said.
"So it's a reasonable assumption for the ministry to assume that a majority of these women are actually receiving their care from a DHB service."
Pregnant women living on the West Coast and in Counties Manukau were the least likely to have registered with a midwife. Women aged under the age of 20 and Pasifika women were also less likely to register for maternity care within their first trimester.
Dr Gray said services needed to be targeted to the people and areas in greatest need.
Even though the ministry does not know who is caring for more than 10 percent of the country's pregnant women, things have improved since five years ago - when about 15 percent were not registered with a midwife or a GP.