A Chinese city plans to fine mothers who have a child out of wedlock, sparking criticism that the policy is discriminatory and could lead to an increase in abandoned babies.

Wuhan city says the rule is aimed at keeping the birth rate low.

One expert says it is the first time that out-of-wedlock children have been expressly singled out for penalty by one of China's municipalities, which have flexibility in how they enforce national population-control policies.

It comes days after the rescue of a young single mother's newborn from a sewer pipe in eastern China prompted discussion over the stigma that single mothers face.

Chen Yaya of the Shanghai Academy of Social Sciences warned there could be more "sewer babies" if the policy is enacted.