When I was pregnant with my twins, I resolved to nurse them exclusively no matter what. I knew about breast milk’s many health and developmental benefits, so I did everything possible to ensure my success. I reached out to mothers of multiples, found a great lactation consultant, and even bought a special pillow designed to help me feed both babies at once. Then Thomas and Elisabeth were born… and reality intervened. Because they each had difficulty latching on and I didn’t make enough milk to feed them both, my infants wound up getting a combination of breast milk and formula.

In those first few weeks, I was disappointed in myself. But then I learned that many pediatricians and nursing experts support the practice of combination feeding. “You should feel good about whatever nursing you can do, because every little bit makes a difference for your baby,” says Freda Rosenfeld, a certified lactation consultant in Brooklyn, New York. Formula contains all the nutrients your baby needs, and introducing it — whether during the first few weeks or a few months later — doesn’t necessarily signal that your nursing days are coming to a close anytime soon. Combination feeding makes particular sense in these three scenarios.