All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, sallallaahu 'alayhi wa sallam, is His slave and Messenger.
A woman who is breast-feeding a baby or is pregnant and expects harm to herself or her child (due to fasting), may break fasting and make it up later. So you have to fast a day in place of each day missed. The same applies to you if you break your fast fearing for your child. However, if you break your fast fearing for your child alone, then you have to make up the missed days in addition to giving an expiation for each day missed, and you should offer the expiation to the needy.
As for the six days of the previous Ramadan, if you are still pregnant or could not fast due to any serious illness or due to you breast-feeding your baby, then you should make up for these missed fasts after the coming Ramadan. If there was a period following the last Ramadan when you could fast, but you did not fast without any legal reason, and after that period you became pregnant and was not able to fast before the coming Ramadan, then you must make up the missed days and offer an expiation for each day.
We ask Allah to bless you and your children.
Allah Knows best.