I found this aspect of my second pregnancy scary and each night before a scan I got a bit worked up (I'm a habitual worrier) and then everything would be fine.
I was upset, worrying that it was because of something i had done. My extensive research in forums and on Google taught me that there was no real reason for Baby N being a tiddler, he just was (and still is) a skinny bean.
Did you have any extra scans during pregnancy? Even if they're for something a bit scary, it's nice and reassuring to see baby.
Thanks for reading, C x
(Please note, this post is based upon my experience and it is in no way offering any sort of advice - if you are worried, talk to a midwife or doctor without delay)