Is Plastic Surgery Haram?
Question

If a woman's body has been altered so much during her pregnancies that she feels ashamed to show herself in front of her husband, is she allowed to have plastic surgery?
Praise be to Allah.Ruling on performing plastic surgery
Your question revolves around the ruling on performing plastic surgery, on which we will give you a brief summary.
Doctors who specialize in plastic or cosmetic surgery define it as surgery performed to improve the appearance of part of the body. This may be done by choice, or because it is necessary.
Plastic surgery that is considered necessary is that which is done when there is a need for it, when something does not look right, when something is missing, if there is too much or too little of something, or because something has been destroyed or deformed . At the same time, it is regarded as cosmetic surgery because it results in improved appearance.
Types of faults that necessitate plastic surgery
Faults may be of two types: physical or congenital faults and faults which result from illness. Congenital faults include abnormally turned-out lips , hare-lips, twisted fingers or toes, etc. Faults which result from illness include the scars left by leprosy or other skin diseases, or scars caused by accidents and burns. 
There is no doubt that such faults and scars cause physical and psychological pain and harm, therefore Islam allows people afflicted with them to remove or reduce them by surgical means. They cause the kind of mental and psychological pain that allows this surgery as an urgent need, where necessity permits something that is ordinarily forbidden. 
Any cosmetic surgery which comes under this heading of need because of the fact that the reason for the surgery is causing harm is permissible, and is not considered to be changing the creation of Allah.
Plastic surgery: Difference between what is permitted and what is forbidden 
To further understand the difference between what is permitted and what is forbidden, we will quote the words of al-Imam al-Nawawi in his commentary on the hadith: 
“Allah has cursed the women who make tattoos and the women who have this done, the women who pluck facial(eyebrow) hair and the women who have this done, and women who widen the gap between their own or others teeth for the sake of beauty, changing what Allah has created.” (Sahih Muslim, 3966)
Al-Imam al-Nawawi (may Allah have mercy on him) said: 
“The woman who tattoos is one who uses a needle or similar implements to prick the skin of the hand, wrist, lips or other part of a woman's body until she draws blood, then she puts dye into the wound. It is haram to do this or have it done by choice. Similarly, plucking or removing hair from the face is also haram, whether one does it or asks someone else to do it for one, unless a woman has a beard or moustache, in which case it is not haram to remove it. Widening the gap between the teeth is done by filing between the incisors. This is done by old women to give the appearance of youth and make the teeth look beautiful, because this attractive gap between the teeth is characteristic of young girls. When a woman gets old, her teeth get big and look ugly, so she may file them to make them look more attractive and give the impression that she is younger. It is haram to do this or have it done by another, because of this hadith, and because it involves changing what Allah has created, and is a form of deception and falsehood. Widening the gap between the teeth is something that is done to make a person look beautiful, which indicates that what is haram is when this is done in the pursuit of beauty, but if it were done as a form of treatment because of some problem or deformity in the teeth, then there is nothing wrong with it. And Allah knows best.” (al-Nawawi, commentary on Sahih Muslim, 13/107)
We should point out here that cosmetic surgeons do not distinguish between cases of serious need and other cases. Their concern is to earn money and satisfy their customers. Materialists and proponents of freedom think that man is free and can do whatever he wants with his body, but this is wrong; the body belongs to Allah and He can command whatever He wills concerning it. 
Allah has told us about the ways in which Iblis (Shaytan) promised to lead people astray, one of which is (interpretation of the meaning): “and indeed I will order them to change the nature created by Allah.” [al-Nisa 4:119]
Haram cosmetic surgical procedures
There are cosmetic surgical procedures which are haram and are not considered to be excusable; these are seen as tampering with the creation of Allah for the sake of beauty. Examples include: breast enlargement or reduction, and procedures aimed at reversing the signs of ageing, such as face-lifts etc. 
The Islamic view is that these are not permitted, because there is no urgent need or necessity for them; rather, the aim is to change and tamper with the creation of Allah for reasons of human vanity. This is haram and the one who does it is cursed because it involves two things mentioned in the hadith: pursuit of beauty and changing what Allah has created.
Added to this is the fact that these operations are aimed at deceit, and may involve the injection of materials extracted from aborted foetuses. These are very serious crimes. Moreover, many of these operations result in ongoing pain and other side effects, as the specialists themselves say. (See Ahkam al-Jirahah (Rulings on surgery) by Dr. Muhammad Muhammad al-Mukhtar al-Shanqiti).
On the basis of the above, we say to you: if the disfigurement that you are dealing with is incidental and is causing you severe embarrassment as well as putting your husband off, for example, and you are not doing this operation for the purpose of making yourself more beautiful, but only to remove or reduce an accidental disfigurement, then there is nothing wrong with doing it, in sha Allah. 
And Allah knows best.