Some of her family members had been saying she may be feeling sick because she's carrying twins, Mrs McKay said.

"I thought probably not, but I was kind of curious," she said.

"I went for a scan and said to the sonographer, 'I just want to make sure there's only one in there'. I figured within 30 seconds he'd be like, 'yep, one healthy baby'.

"It was a massive shock.

"Straight away he said, 'yeah, you're definitely having twins'."

She was initially excited at the idea of twins, but things changed with the sonographer's next words.

"About 30 seconds later he said, 'wait a minute, actually, there's another one'," she said.

"I wasn't excited anymore. I was a bit like, oh my goodness, this is the Twilight Zone, I can't do triplets.

"Literally, my jaw dropped. I didn't speak for the rest of the entire ultrasound."

Mrs McKay wondered how her body was going to cope, as she was only a size six.

"It was pretty crazy."

Mrs McKay said two weeks ago she gave birth to three beautiful girls - Evolet, Vashti, and Sophie.

"Two are identical, and one is fraternal," she said.

Though Mrs McKay initially hoped for a natural birth, it wasn't possible.

"I'm so excited I managed to get them to 35-weeks gestation, so I think that's helped. The average gestation for triplets is 32-weeks," she said.

The girls weighed 1.97kg, 2.08kg, and 1.93kg.

"I'm very excited. Obviously I'm not under any illusion - it's going to be massive. I guess I'm possibly making it harder for myself because I'm committing to cloth nappies, and I'm also determined to breastfeed.

"I reckon we're going to give this our best shot, and we're going to do it."

The triplets weren't Mr and Mrs McKay's first children.

"My husband and I have a three-year old, Micah, and my husband also has two older children," she said.

"So all of them are very excited about the triplets."

According to the latest statistics from the Australian Institute of Health and Welfare, 4516 mothers had multiple births in 2017.

In Tasmania there were just 85 multiple births that year.

According to the data, multiple pregnancies represented just 1.5 per cent of pregnancies. Almost all were twins, with just 1.2 per cent triplets, quadruplets, or higher.

Despite this the number of multiple births has been increasing, the report said.

This coincided with increasing maternal age at birth, and the use of assisted reproductive technology.