Will I Be Punished Even If I Repent from Zina?
Question

I have a friend who got to know a man 6 years ago. Praise be to Allah, they have got married, but before that they committed zina. My friend deeply regrets what she did, she weeps night and day and offers all the prayers and prays for forgiveness every day. After getting married, they went for ‘Umrah and they intend to do Hajj, but her husband wants children and she is afraid that she will produce a deformed child as a punishment from Allah. She says that the one who commits zina will be punished in this world and in the Hereafter even if he or she repents. Is this true? Will they go to Hell?.
Praise be to Allah.Repentance: Your way to forgiveness
We praise Allah for having enabled your friends to repent, and we ask Him to reward them and make them steadfast. Undoubtedly the immoral actions that they committed are causes of Allah's punishment in this world and in the Hereafter, but there is the hope that sincere repentance from this action, regret for what was done, resolve not to do it again, and weeping for having sinned against Allaah and violated the sanctity of the Muslims will all be good for this repentant person and will be the cause of his or her bad deeds being turned to good deeds. 
Never despair of Allah’s mercy
This sister’s repentance should not lead her to despair of the mercy of Allah, for the Shaytan will exploit this and will prevent her from repenting and doing good deeds. 
It is good that she regrets what she did and weeps and repents and prays for forgiveness, out of recognition of the seriousness of the sin that she and her husband committed. But it is not good for her to despair of the mercy of Allah and think badly of Him, may He be exalted. 
Our Lord has told us that He forgives all sins, no matter how great they are or how many, if we repent to Him, and He has forbidden us to despair of His mercy, as He says (interpretation of the meaning): 
“Say: O ‘Ibadi (My slaves) who have transgressed against themselves (by committing evil deeds and sins)! Despair not of the Mercy of Allah, verily, Allah forgives all sins. Truly, He is Oft-Forgiving, Most Merciful” [al-Zumar 39:53]
And He has told us that He will turn evil deeds to good deeds for the one who is sincere in his repentance, even if he has committed shirk and murder and zina, which are the gravest of sins. Allah says (interpretation of the meaning): 
“And those who invoke not any other ilah (god) along with Allah, nor kill such person as Allah has forbidden, except for just cause, nor commit illegal sexual intercourse -- and whoever does this shall receive the punishment.
The torment will be doubled to him on the Day of Resurrection, and he will abide therein in disgrace;
Except those who repent and believe (in Islamic Monotheism), and do righteous deeds; for those, Allah will change their sins into good deeds, and Allah is Oft-Forgiving, Most Merciful” [al-Furqaan 25:68-70]
Will I be punished even if I repent from zina?
Our Prophet (peace and blessings of Allah be upon him) told us that Allah rejoices over the repentance of His slave and that the one who repents from sin is like one who did not sin. 
Hence we can see that it is wrong to say that the one who commits zina will be punished in this world and in the Hereafter even if he repents. The evidence quoted above proves that this idea is false. Rather Allah encourages His slaves to repent and rewards them for it if they do it; He does not punish them. 
So there is no need to fear having children and no need to be anxious. 
Ask Allah for righteous children, and seek the help of your Lord, and do many good deeds. We ask Allah to help you to do that which pleases Him. 
And Allah knows best.