The legal amendment would give new teeth to a government campaign to outlaw the selective abortion of female foetuses and correct an imbalance in the ratio of boys to girls that has grown since China's one-child policy was introduced more than 20 years ago.
An Jian, a member of China's parliament who discussed the amendment over the weekend, was quoted as saying: "The revision is aimed to prevent the selection of a child's gender when not conducted for medical purposes."
"Artificial gender selection can jeopardise China's population structure, leading to social instability," An wrote in a report.
Government figures show 119 boys are born for every 100 girls in the world's most populous nation.
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The Chinese tradition of preference for sons - seen as carrying the family name and being able to provide for their parents in old age - was bolstered after the one-child policy was introduced to curb China's population, now over 1.3 billion.
Chinese tradition favours sons
for carrying the family name
Sex-selective abortion is banned, but ultrasound has made it easier to know a baby's gender in advance, increasing the chances for aborting girls.
"The amendment specifies that anyone who assists others with gender selection will face heavy fines and a three-year jail sentence," the China Daily said.
China has vowed to reverse the trend of its gender imbalance by 2010. It previously launched a tentative scheme to pay moderate pensions to rural parents with no sons and educate them that "girls are as good as boys".