There's always reasons for every life event.
Pre-pregnant, my weight was 55kg. Post-delivery, after about 3 months, my weight returned back to 55kg. But since I was breastfeeding Aisya, my weight decreased little by little until I reached about 50kg after 1.5 years breastfeeding her. Many say that breastfeeding the a good way to lose weight. As for me, yes I did lose weight, but maybe a little too much....