Migrant women working in rural Australia are raising their newborns in sheds shared with 10 men, living on isolated properties and being hounded to pay hefty medical bills.

One woman, who came to the country under the federal government's Pacific Australia Labour Mobility (PALM) scheme to work in northern NSW, abandoned her baby in a motel room.

These are the kinds of desperate scenarios observed by health and social services in the Coffs Harbour region, a state parliamentary inquiry into modern slavery has been told.

There are an estimated 40,000 workers enslaved across Australia, subject to low pay, restricted movement, punishing hours, as well as poor housing and healthcare.

Those in rural areas are considered particularly vulnerable due to isolation and their dependence on unscrupulous labour hire companies that recruit agricultural workers.

Ruth Dooley, who volunteered at a recently shuttered pregnancy support service called Lilyrose, said migrant women often lived in grim conditions after giving birth.

At the urging of the local hospital, the charity helped one new mother who had no money or support.

"Her home was a glorified shed out on an isolated property and reached by a perilous track," Ms Dooley told the inquiry sitting in Coffs Harbour on Thursday.

"The toilet was an outside portaloo ... very, very rough, basic conditions."

The local health service then tried to bill Lilyrose, a religious not-for-profit, nearly $3000 for the woman's hospital care.

Another mother had to bring her newborn back to a shed she was sharing with 10 men, before being moved to a motel room already occupied by another family, Ms Dooley said.

Several women were approached by hospital billing staff while in active labour or while recovering from caesarean sections, as few had health insurance.

The inquiry has previously heard migrant workers are increasingly seeking healthcare in late pregnancy, or being coerced by their partners or employers to get abortions.

Clinical nurse consultant Alexandra Wade said two children of PALM workers were recently taken into state care, including a baby who was abandoned in a motel room when the mother was deported.

Workers may be reluctant to seek healthcare in fear of what insurance documents could reveal.

"There's a concern that if that there is a record of ... what they've attended for, that at home it might be misinterpreted (as) against their religious practices," Ms Wade said.

Migrant workers were also often "othered" by baseless community gossip about increased crime, St Vincent de Paul Society migrant and settlement manager Biba Honnet said.

"They're kept separate from our local communities," she told the inquiry.

Ms Honnet said she had seen PALM workers living in accommodation with dirt floors and tarpaulin walls, conditions that generally worsened if they left the scheme.

Recent research found there were up to 7000 PALM workers adrift in Australia, usually disengaging from the scheme due to wage theft, poor living conditions or inadequate payment.