Yeah it wouldnt hurt for you to gain some weight drinking those but yes watch the sugar.
im only 108 Pounds 6 Months Pregnant so the Weight Would be a good thing Right
Keep in mind that those are considered "weight gainers". They are also very high in sugar. They are OK to have every now and then but I wouldn't recommend them every day. There are far better alternatives.
Im 34 weeks and I've had a BIG glass of carnations every night before bed and my little man is three weeks ahead in growth and healthy as can be. So yes it's fine. I recommend it, your body could use the extra calcium.