It is a common misconception that, because something occurs naturally in the body, it is safe to take as a supplement. For example, the body naturally produces formaldehyde in beneficial quantities, but taking too much could lead to adverse outcomes. Phosphatidylserine isn't indicated for curing sleep difficulties and, in fact, can lead to sleep difficulties. It can also interfere with some other medications: https://www.webmd.com/vitamins-and-supplements/phosphatidylserine-uses-and-risks
There have been no studies establishing the safety of use during pregnancy, so it is best for your wife to consult her doctor before taking anything.