A woman from Kiama Downs was forced to undergo an emergency caesarean after she says she became violently ill after eating a hot chicken roll from a Sydney bakery suspected of being at the centre of a food-poisoning outbreak.

First-time mother Ashley Buchanan remains in Wollongong Hospital after giving birth to her daughter, Ava, on Tuesday, five weeks before her due date.

Mrs Buchanan said she and her husband, Caine, had travelled to Sylvania, in Sydney's south, for a birthing class at the weekend when they stopped at Box Village Bakery and Cafe for lunch about 1pm. Both she and her husband ate hot chicken rolls with gravy, she told the Illawarra Mercury from her hospital bed on Friday.

By 8pm, Mrs Buchanan was violently ill with intense cramping, vomiting and diarrhoea. Mr Buchanan drove her to Shellharbour Hospital about 1am on Monday. By then, he too was experiencing some of the same symptoms.

Mrs Buchanan was transferred to Wollongong Hospital, where doctors kept watch on her falling blood pressure and worsening loss of fluids. Doctors decided to operate when unborn Ava's movements slowed.

Mrs Buchanan told radio station 2UE earlier that she was admitted to the hospital's intensive care unit (ICU) after the surgery.

"It was all quite frightening, because my blood pressure went right down; they had to rush me to ICU straight after the delivery," she said.

"My husband was actually in hospital at the time, but because he was sick he wasn't allowed to come into the theatre with me to see the birth, so it was all very stressful and frightening."

"It wasn't until the next day they told me they were so lucky that they made that call, because once they started the caesarean they found I had internal bleeding so it could have ended up much worse if they waited," Mrs Buchanan told the Mercury.

Baby Ava ultimately arrived at 35 weeks and six days, weighing a healthy 2.9 kilograms.

Doctors told the family a younger baby of a lesser weight might not have withstood the stresses of food poisoning.

Mrs Buchanan told 2UE she could not see her daughter for the first 24 hours while she was in ICU.

She said the whole experience was terrifying "for your first child, or any child I guess. You don't expect the birth to pan out like that."

She said her daughter was healthy and doing well, and for that she felt blessed.

She also warned other expectant mothers to be wary of what they ate.

"I've been so careful with everything I've eaten [during] my whole pregnancy. I opted for the hot chicken roll. I could see that the chicken was in the hot stand; it was steaming.

"I thought, 'I should be right.' But, warning to all pregnant women, just be so careful. It's not worth it," she told 2UE.

"I can't eat still - I can't even hold down a glass of water yet," Mrs Buchanan told the Mercury. "I'm pretty drained."

The NSW Food Authority shut down the bakery this week after more than 150 people presented themselves at St George and Sutherland hospitals with symptoms of food poisoning. Tests confirmed that salmonella bacteria had been found in some of the patients who had eaten at the bakery.

The South Eastern Sydney Local Health District said 151 people had now presented themselves at Sutherland and St George hospitals with food poisoning, and 27 had been admitted to those hospitals.

One angry father, Ross Paull, placed a note on the door of the bakery this week, saying "You made my family very sick!!"

In response, a hand-written note was placed on the bakery's window that read: "Dear Customer. We are realy (sic) sorry about what happen. We hope everyone get well soon. We are sorry again."

This week, Professor Mark Ferson, the director of the Public Health Unit at the South Eastern Sydney Local Health District, said the sick patients ranged in age from young children to the elderly.

"They've presented with diarrhoea, vomiting, stomach cramps, fever, aches and pains, and we have some positive salmonella results on early tests on some of those people," he said.

"Salmonella infection can be mild, but can be very nasty. People can get dehydrated and quite sick with salmonella."

Salmonella is mainly spread to humans when they eat under-cooked food made from infected animals. Symptoms often start six to 72 hours after infection and usually last for four to seven days, although they sometimes last longer.