Nikaah & Marriage Issues

Status of the marriage if one member is involved in constant zina

Q: I wanted to ask if there is a lady and she has a husband who has had an affair which she recently discovered was also physical in nature for 2 years or so with a married woman, is the nikaah nullified for the wife?

As this husband continues to commit adultery and simultaneously have relationship with the wife? If the marriage is not nullified, what dua should one make for reconciliation after such deceit?

Glad tidings in the mubaarak Ahaadith for a lady who had a miscarriage

Q:

1. I had a missed miscarriage at 8 and half weeks of pregnancy. I conceived at a late stage as I was blessed with nikaah much later in my life. I am much devastated with the miscarriage.

My question is, will the miscarried foetus go to heaven or it never existed (as if there was no rooh in it)?

2. Furthermore, I had a dnc done but after three weeks post procedure I'm still bleeding. Please advise on the process for salaah and Quraan. 

Authenticity of a hadith regarding duas being accepted during childbirth/labour

Q: I came across some information a few years ago, which I don't remember the source. I am now pregnant alhamdulilah and I would like to verify this information as I cannot find anything in my Islamic literature.

Is true that dua is accepted during childbirth/labour? If so, please can you provide any basis.