A woman was forced to have an emergency caesarean section after a doctor missed abnormalities in a scan done 16 weeks before the birth.

Deputy Health and Disability Commissioner Rose Wall today released a report detailing Pacific Radiology Group and a radiologist in breach for failing to identify the woman's placenta was low-lying on a second trimester ultrasound scan report.

The "critical" error left the woman in risk of life-threatening bleeding.

Failures started when the woman had a routine ultrasound at 19 weeks of pregnancy. The sonographer recognised that the placenta appeared to be low lying, but forgot to note it on her worksheet.

The radiologist who reviewed the worksheet and the sonography images then recorded that the placenta was not low lying. As a result there was no further antenatal scan to assess placental position.

In the report, Wall criticised the radiologist saying it was his responsibility to review the images carefully, irrespective of what was written on the worksheet.

At 36 weeks of gestation, the woman was rushed to hospital with vaginal bleeding.

The obstetrician reviewed the 19-week scan and ruled out placenta praevia, which had been her initial suspicion.

Instead, the woman's bleeding was diagnosed as a mild abruption, and an induction was started.

The correct diagnosis was not made until the following day, and the woman then underwent an emergency caesarean section which was complicated by excessive blood loss with the placenta low lying and abnormally adherent.

Subsequently, the newborn spent nine days in the neonatal unit. Luckily, both mum and baby survived.

In the report, the radiology service advised that this case had led to a significant improvement in ultrasound accuracy.