Being the parent of a newborn can be one of the most stressful and challenging jobs, and any little thing can help. Newer gadgets called infant formula makers are claimed to make precisely measured, warm, ready-to-drink bottles.

But are they worth the money, and more importantly, do they work? Here’s what a Consumer Reports investigation found.

A big selling point for these infant formula makers is that they’re a tech-savvy solution that’s presumably more accurate than relying on your hands and tired eyes. Manufacturers say the devices will take some of that work off your plate and reduce the stress in your life.

But after complaints from caregivers and medical experts to the Consumer Product Safety Commission about the Baby Brezza Formula Pro Advanced, Consumer Reports safety experts investigated the accuracy of three of the more popular machines on the market right now: the Baby Brezza Formula Pro Advanced, the Baby Brezza Formula Pro Advanced WiFi, and the Baby Exo Formula Dispenser Machine.

The results were concerning.

The two Baby Brezza formula makers consistently gave less formula than was expected, which over time could lead to your baby being malnourished. The Baby Exo consistently gave more formula, which also isn’t ideal.

In a statement sent to CR, Baby Brezza said the reason for the discrepancy in test results was because of the significant natural variability that exists in formula powder in general. Baby Exo didn’t respond to CR’s request for comment.

While these formula makers may save you time, it’s important to feed your baby accurate amounts of formula. So preparing it by hand and following the manufacturer’s instructions or those from your pediatrician may be your best choice.

It’s important not to make homemade formulas because there’s no guarantee your baby will be getting the proper nutrition and it could be contaminated with harmful bacteria.