For newborns, the first 4-6 weeks are the same as daytime, you are changing every few hours if not sooner at night, since when they wake to eat they have usually had a bowel movement that needs attention. Around 4-8 weeks they will stop having these bowel movements at night, and most babies can continue with their daytime diapers but with slightly increased absorbency for the next month or two.
If your child is a heavy wetter (meaning your daytime diapers are pretty saturated in an hour or so, and nighttime is a few hours at best), this is the time frame where you will see the need to upsize your nighttime diaper from your daytime diapers. The amount of stuffing needed for heavy wetters will typically cause an upsize well before the daytime diapers need this to happen. Sme of our favorite daytime diapers, like bumgenius, Thirsties fitteds, AIOs, are just not equipped for nighttime. What you love about them during the day is what works against you at night. The trim contours, thin fit, and quick to wash and dry is not adequate to hold the amount of stuffing needed that causes leg gaps and leaking at night.
For specific fit issues, please email us, but before buying a boatload of new things, we can help you use what you already have and piece things around that to make nighttime work. Most of you have the absorbency needed, it is the “shell” that will change, the cover, the pocket, something on the outside to help the inside “stuff” work well for your baby. Pajamas make a difference, too. As cute as they are, most heavy wetters will not do well in two piece pajamas, unless the bottoms are really loose in the elastic and do not pull down on the diaper. One piece sleepers, tee-shirts or long sleeve shirts with leg warmers or long socks, are better choices. The pants on many pjs will pull down on the diaper, causing leg gaps at the bottom of the crotch, and letting urine seep out. Cloth at night is possible, with a few tweaks it can be easy and work for your family~