I know a girl who wants to get married but she wants to finish her university so she doesn't want children until she finishes university is it allowed to use condom or pills to avoid having children?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

There is no harm in delaying pregnancy in order to achieve a permissible benefit as Allaah permitted it for a need. Imaam Muslim reported that a man came to the Prophet and told him: 'I have a slave girl who is our servant and I have intercourse with her, but I do not wish that she becomes pregnant.' So the Prophet remarked: "You can practice coitus interruption if you so wish."

There are many means for preventing pregnancy, and they differ based on the physical harm that they might cause, or the violation of religious limits they include or may lead to, so one has to use the easiest means. The harm is defined by doctors who specialize in this field.

The spouses are advised to practice natural planning as one of the beneficial methods, which is avoiding sexual intercourse when the egg is ready to be fertilized; the egg is at this stage at regular times, so one can know this by asking doctors.

Finally, the following matters should be noted:

     1)      One of the objectives of the Islamic Law in marriage is to have children, so whenever a Muslim can achieve this objective, he should not delay it.

     2)      The study of the woman should meet the religious requirements, for instance the field of her studies should be in accordance with her nature. Besides, she should abide by Hijab when going out, avoid forbidden mixing of men and women and so forth. 

For more benefit refer to Fatwa: 87376.  

Allaah knows best.