Many doctors unqualified to do Down's screening

PUBLISHED : Thursday, 10 December, 2009, 12:00am
UPDATED : Thursday, 10 December, 2009, 12:00am

More than half of the city's obstetricians are not qualified to perform prenatal Down's syndrome screening, possibly leading to errors and unnecessary panic among expectant mothers, according to a university study which polled one-third of the city's 300 or so childbirth specialists.

Only 45 per cent of the 106 surveyed had accreditation to perform such scans, Chinese University said yesterday. Yet 73 per cent said they offered universal screening to all pregnant women, and 62 per cent performed NT scanning, a scan which can determine a risk of Down's syndrome in a fetus.

The NT (nuchal translucency) scan can determine if a fetus has too much fluid behind the neck, indicating a risk of Down's syndrome. A separate blood test can determine levels of abnormal protein and hormones. If both tests indicate a higher risk, a woman may need to undergo invasive tests.

But researchers said the NT scan was 'highly operator-dependent', meaning that for accuracy it should be 'performed by well-trained, certified sonographers who also undergo regular quality control and auditing'.

Eight of the 35 doctors who did not have accreditation but who performed NT scans, did it at the wrong time. Six doctors did it too early and two performed scans too late. It should be performed between 11 and 13 weeks into pregnancy. Only 23 had received formal NT scan training. But all accredited doctors did their scans at the right time. Doctors with accreditation performed 21 to 50 scans a month, while those without performed six to 10, the survey showed.

Professor Lau Tze-kin of the university's obstetrics and gynaecology department said a poorly done NT scan could highly exaggerate or underestimate a women's risk level. He said an NT scan should only show the fetus' head and upper chest, but many poorly done graphs also showed the lower body, making it difficult to determine how much fluid there was behind the neck.

Other poorly done scans could even double the risk level, he said. He urged Hong Kong obstetricians to apply for accreditation as soon as possible. He said pregnant women should also know that NT scans should only be performed when the fetus was 45mm to 84mm long.

A private gynaecologist, Robert Law Chi-lim, said that although many doctors did not have accreditation, they had attended classes and were 'competent' to do scans. 'Many doctors just do not bother applying for accreditation, which involved submitting many documents,' he said.

He said the Hong Kong College of Obstetricians and Gynaecologists did not have accreditation guidelines and unless 'there was evidence of grave mistakes', the system had been running well.

Wrong timing

An NT scan should be done between 11 and 13 weeks into pregnancy

Of the 35 doctors who did not have accreditation, this number performed NT scans at the wrong time: 8