Horror Sydney car crash kills pregnant woman, her unborn twins and 17yo learner driver.

Two young women, one of whom was heavily pregnant and expecting twins, have died in a four-vehicle crash in Sydney’s west while two men remain in a critical condition in hospital.

A female driver, 17-year-old Anh Hoang, and her pregnant sister-in-law, 23-year-old Katherine Hoang, were in a Nissan Tiida on Northern Road, Orchard Hills about 7.40pm on Friday when there was a collision with a Mazda 3 driving in the other direction, NSW Police say.

Both women died at the scene and the unborn babies did not survive.

NSW Ambulance Acting Inspector, Joe Ibrahim, said the responding paramedics did an amazing job at the “distressing” scene but “there wasn’t anything they could do for those two people who have lost their lives”.

The right support services are being offered to those emergency services workers, he told AAP on Saturday.

A 25-year-old man travelling in the front seat of the same car was placed in an induced coma at the scene and rushed via highway patrol escort to Westmead Hospital with head and abdominal injuries, Insp Ibrahim said.

He remains in a critical but stable condition.

The sole occupant of the other car, a 29-year-old man, was trapped for a short time then taken to hospital in a critical condition with significant limb injuries, pelvic injuries and potentially mild head injuries, Insp Ibrahim said.

He remains there under police guard.

The impact of the collision forced the Nissan backwards, damaging two other vehicles whose drivers – an 18-year-old man and 23-year-old woman – “took evasive action” to avoid the incident and escaped injury, police say.

Any witnesses to the crash, near Glenmore Parkway, or those with dash cam video are asked to come forward.

Meanwhile, a woman has been killed during a single-vehicle crash in Sydney’s south west about 1.20pm on Saturday.

The woman, aged in her 20s, was driving a Hyundai Getz near Wilton when it left the road and hit an embankment.

In the NSW Hunter Valley, a man died early on Saturday after a suspected hit and run near Singleton.

Police say the body of a 44-year-old man was found beside Carrington Street in Glenridding about 5.35am.

The scene will be forensically examined but inquiries suggest he was struck and killed by a car after 4am.

Officers would like to speak to anyone who may have seen a silver hatchback which reportedly pulled up alongside the body at 5.30am, with the female driver getting out to check on the man before driving away.