How does this work with people having a single child? This might have been feasible in the past, with multiple children, but now, the woman becomes part of her

How does this work with people having a single child? This might have been feasible in the past, with multiple children, but now, the woman becomes part of her husband's family or vice versa so(but I presume the former, since having a daughter is so undesirable in China), 50% of the parents get the short stick?