Weight?

Melissa • 26. I love my husband and so thankful for my friends & family. We're expecting our first little one.
I usually don't like "how much weight should I have gained" posts but I am currently 27w1d and have picked up 4kg only.. I was 53kg before birth and I'm quite short (154cm). Is this too little weight? Anything to be concerned about or does it just vary from pregnancy to pregnancy?