Two people have been detained by police in Shanghai on suspicion of killing a baby born with a cleft lip, Chinese state media report.
The two-day-old baby was found dead by doctors at the No 2 People's Hospital in Chongming County last Friday, said the Xinhua news agency.
Those arrested are a doctor and the baby's grandfather, who is accused of injecting the baby with chemicals.
Cleft lips are a common birth defect but easily corrected.
Cleft palates, where a baby is born with a hole in the roof of the mouth, are more severe. The condition causes feeding difficulties and can also lead to problems with hearing and speech.
Xinhua said initial investigations indicated the grandfather had killed the baby by injecting him with potassium chloride, a drug used to treat potassium deficiency but which can stop the heart when used incorrectly.
The doctor, from the gynaecology and obstetrics department, is accused of supplying the drug and telling the grandfather how to use it, Chinese media reported.
Beam International (Future Smile in China), one of several charities which carries out free surgery for the condition, told the BBC that about one in 600 babies born in China each year have a cleft lip or palate.
Surgery for cleft lips can cost between 5,000 ($800; £520) and 7,000 yuan in China, and for cleft palates up to 10,000, said the charity's China director, Shan Li.
Babies who struggle to feed and whose families cannot afford treatment or find a charity to help them would often not survive, she said, while some people may have to save for years to pay for the surgery.
There have been previous reports of families abandoning such babies.
In May this year, one baby with a cleft palate was found in alive in the Guangxi region, 10 days after being left in the countryside.