Why Does A Child's Behaviour Change When The Mother Could Be Pregnant?

They can become jealous of the prospect of a new sibling and the for seen lose of their position as the only focus. Pregnancy takes away from what the child knows and attention it has received. The loss of this full focus can make them react in order to attract the attention back on themselves.

Bcoz she is strat caring for that child that going to come on earth  more than that is  beside her

she always think about that child that is in her abdomen   

When a mother becomes pregnant with another child her other child's behavior may change because they are used to being the only one receiving all the attention and also the mother may become more emotional during pregnancy herself causing her child to become more emotional.

This is normal it's a worrying time knowing you won't be the baby of the family anymore to stop these worries you need to heavily include your child in this pregnancy take them to appointments, scans, say I'm going to need a little help from you with feeding, dressing the new baby and when the new baby arrives buy a present for your child and say this is from your younger brother/sister it will make the child feel more protective over the new sibling keeping the child involved is the key to calm here  

They start to worry that they are going to lose the attention that they are used to always getting. Its totally normal they just have to adjust to the change which over time they will. When it gets closer to time for the baby to arrive that jealousy may turn into excitement. Just try to explain to them that they will be the older brother/sister and that they are going to be  wonderful at it. That should make them feel better about the situation and they will probably look out for baby bro/sis

Include your child in your pregnancy, let him/her listen to your baby on your belly, let her feel the baby move and kick, get your child really involved .  tell them how they can help dress the baby keep the baby safe, warm...let them know they will have some one to play with, teach...she gets to be a teacher, teaching to talk, walk, etc....help feed the baby. Make her feel like she will be the best thing that ever happened for your new baby....explain...explain...explain...she/he can even help pick out clothes for baby,etc...involve your child...it's normal for a child to be a little jealious...but you can change that behavior, even let them go with to sonagrams/ultrasound...

Well they will start acting different because they are afraid of losing you. They think that you will move to the new child. So remember to give them lots of attention!!!

Because they are happy that their having a brother ,or sister. They also have to change their behavior because they have to help their mother and father take care of their brother ,or sister.

Mostly bc the attention is not on them as much anymore..