The articles, including some on leading Vietnamese news websites, offer advice on sexual techniques, food and drink and timing intercourse so as to purportedly determine the sex of one's baby.

"Sex selection in reproduction is worsening the gender imbalance in Vietnam," said Tran Van Trung, chief investigator of Vietnam's Ministry of Health. "Our country's ratio of boys to girls has reached an all-time high."

A study released Wednesday by the UN Population Fund (UNFPA) found the gender ratio among newborns in Vietnam last year rose to 112 boys for every 100 girls, up from 110 to 100 in 2005.

Trung said inspectors were checking websites hosted throughout the country in preparation for a report to the health ministry at the end of May.

He said inspectors had already warned numerous websites publishing information about methods that supposedly ensure one gives birth to a boy to remove the offending content.

"I think the information is obviously not accurate, but people still want to try," Trung said.

One article on the popular news website VnExpress.net advises couples on how to use the ancient Chinese astrological calendar and the parents' birth dates to determine whether a given date of conception will result in a boy or a girl.

Another popular news website, VietBao.vn, advised couples to make love at exactly 3am on the day after ovulation and to eat a low-calcium diet. The website, registered to Vietnam's Ministry of Information and Communication, promised a "success" rate of 96%.

Trung said after the inspection of internet sites was complete, inspectors would move on to checking hospitals and clinics that have ultrasound machines which can detect a foetus's sex.

Vietnamese law bars health staff from telling couples the sex of their unborn child, but the law is widely ignored in practice. Couples that learn their unborn foetus is a girl often abort the foetus and try to conceive a boy.

Trung said inspectors would have difficulty catching doctors or technicians informing parents of their child's sex. He said doctors employ slang to make such information known, calling boys "birds" and girls "butterflies".

Sons are considered more desirable than daughters in traditional Vietnamese culture.

Deutsche Presse Agentur - June 1st, 2009