Do I need to go for a new lottery , if I had H1B previously but had resigned from work and went on H4.

I have H1B and I am working for employer A. Employer A has out be to work at client company B and my job contract with B expires March, 2019

What happens after March? Does Employer A find me another contract? How much time can be off work before they can find me another job and start paying me?

Scenario 2 : I am expecting a child in May 2019 so , assuming that company A is still trying to find me another contract - can I ask them to find me a contract starting August - to stay home with my new baby. What will be impact on H1B?

Scenario 3: Say company A realizes that they don’t want to find me another job after March and obviously no other company will hire me because at that time I will be 7 months pregnant - Can I then resign and go on H4 status? Once I decide to join work back, do I still need to apply for lottery process or my previously approved H1B can be reinitiated and transferred to new employer?

Thanks

Prachi