Without Babies R Us, Target sees an opportunity to double down on its own baby business.

The retailer is expanding its in-house brand Cloud Island, which currently sells items like crib sheets, stuffed animals and baby bath toys, to include essential items like diapers, wipes, toiletries, utensils and bowls. The launch of about 30 new items happens Sunday. Target says most goods will be priced under $10 — 30 to 40 percent less expensive than comparable national premium brands.

When Toys R Us liquidated its business last year and shuttered its Babies R Us stores, many retailers saw an opportunity to flood a suddenly underserved market. Walmart rolled out a revamped landing page on its website for baby items. Amazon quietly started selling a new diapers branded Earth + Eden.

Target had already started to remodel the spaces in its stores where it was selling things like cribs and strollers, putting more of those bulkier items on display and rearranging them so that they were near kids clothing and other overlapping categories. It started letting parents test out more items like car seats in stores before they buy them. And Target says those revamps are leading to sales increases.

"There is a mom out there that's registered with Babies R Us, and all the sudden she's lost," Chief Merchandising Officer Mark Tritton told CNBC. "We've all known how valuable the baby guest is to [Target], how they shop across the total business. ... It's one of our most important guests."

Target has said there's significant crossover with the former Babies R Us and current Target shoppers. The company added, however, that this has always been a core customer group — even before Babies R Us' struggles — that shops and spends more at Target annually than those people without kids at home.

Even singer Beyonce, also a mom, was spotted in the baby aisles at Target earlier this month, next to the diapers.