|The vast majority of babies do not need a liner in every diaper. Most of the time you'll only need a liner at night, long naps or long car trips. Regular daytime changes you'll be using the diaper alone. A few very heavy wetting toddlers using the One-Size do need a liner with each diaper, but that's more the exception rather than the rule and for the most part doesn't come until much later. This is even more rare with the Sandy's as they're a little more absorbent on their own. Newborns especially don't need any liners at all because they're changed so frequently (due to frequent pooping), even at night.
Personally I actually always thought that half as many liners as diapers was actually wayyy too many and I almost always doubled (sometimes even tripled) up at night. But maybe that's just me...
Good luck with the rest of your pregnancy, I'm confident that if you do decide on an ME system that you won't be disappointed.