A Chinese city plan's to fine mothers who have a child out of wedlock has sparked criticism that the policy is discriminatory and could lead to an increase in abandoned babies.

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 China's population-control policies. It also comes just 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 Monday there could be more "sewer babies" if the policy is enacted.

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