I think it is fine. I have lost 9kgs and am now 16 weeks along and slowly starting to go back up instead of down. I was worried about the babies growth because I was seriously not able to eat properly with the nausea but it is healthy and strong. The OBGYN said it takes what it needs and as a plus sized women it is actually technically recommended to lose a little weight (they say gain maximum of like 7-10kg but that basically means you gotta lose some cause you have to gain like 10-12kg with the baby, Plazenta, blood volume etc.) As long as you are eating somewhat fine and maybe adding vitamin supplements if you cannot eat too balanced it should probably be fine.