Hi puj obstruction happens because of outflow tract obstruction down stream. Because your foetus is 29 weeks and there is damage to the kidney it is critical we intervene. Even though the one kidney can do in adult life we do not know the functionalty just now. The increasing dilatation perse is not a worry it could be superimposed hormonal effect but back pressure on the kidney is a concern.at the same time lung maturity is low at this stage of gestation.it is imperative to admit your wife to give a course of betamethasone for foetal lung ripening then plan for delivery along with nicu backup. Once delivered to rescan babies kidney depending on the obstruction plan surgery along with a pediatric surgeon. For more light can also take opinion from paediatricsurgeon ante natally.