Parents across the U.S. have been scouring social media or crossing states to get hold of baby formula amid a national shortage driven by ongoing pressure on supply chains.

The crisis has worsened in the past few weeks as 40% of popular baby formula brands were sold out at U.S. retailers in the week beginning April 24, according to an analysis by Datasembly of more than 11,000 stores. That’s up from 31% less than two weeks earlier, and 11% in November 2021.