How does a spouse declaring bankruptcy affect child support?

The short answer is: not at all. Child support is one of the few types of debts that are not discharged in bankruptcy. In other words, child support debts will not be wiped out, but will instead survive a bankruptcy case. Your spouse will continue to owe child support before, during, and after filing for bankruptcy. 

What's more, child support is not subject to the automatic stay. The automatic stay is a court order that goes into effect as soon as someone files for bankruptcy. It stops their creditors from taking any action to collect on a debt while the bankruptcy case is in effect. It stops wage garnishments and other collection activities, such as repossessions or lawsuits, while the bankruptcy is going on.

However, child support collection actions are not affected by a bankruptcy filing. Nor are wage garnishments to pay child support. Because child support is so important, as a public policy matter, Congress has decided that it should be an exception to the usual rules.