Spitting up does most often mean your baby is full.
When your babies stomach is full then the excess formula will want to come back up if they are still feeding so the baby is likely to spit up.
Also the baby may be having trouble getting the formula down as well which causes them to spit up.
It is OK to not burp a baby at night if they don't need it.
However after feeding your baby it's always best to burp them or at least try to burp them before putting them to bed.
But if the baby is fine they will be okay without being burped.
The baby may simply become fussy and wake you up wanting to be burped.
When you burp a baby you help to force any gas out of their stomach.
Burping a baby may just cause the baby to burp or the baby may also spit up as well.
Burping a baby is where you pick the baby up in your arms and then place them against your chest with their head facing the back of your body and then you pat the baby on the back.
As you pat the baby on the back gently it should cause the baby to burp out gas or air they had built up in their stomach while feeding.
Bottle fed babies usually get the most gas but even breastfed babies can also get air trapped in their stomach as well.
Burping the baby gets that gas or air out of their stomach so that they are not choking on it or become fussy.
After every feeding you should burp the baby or try to burp the baby to make sure the baby has no air trapped in their stomachs.
Otherwise they become fussy and cry and cry until you do relieve that gas in their stomachs by burping them.
Sometimes they may spit up on your shoulder while burping them so have a burp rag or washcloth on your shoulder before you burp the baby.