When a woman is pregnant with a child, all the angels will make Istighfar (repentance) on her behalf. Allah SWT will, for each day of her pregnancy, write for her 1000 good deeds and erase from her 1000 bad deeds.
When a pregnant woman starts to feel the pain from contractions, Allah SWT will write in her records as someone who is doing jihad (spiritual or physical struggle) in His path.
When a woman becomes pregnant by her husband and he is pleased with her, she obtains the reward of a person engaging in fasting for Allah SWT and a person spending the night in ibaadah (worship).
A woman from the time of pregnancy until childbirth and weaning the baby, is like the Mujahid (someone fighting in the path of Allah, swa) who is stationed on the frontiers of the Islamic land. If she dies during this period, she dies the death of a shahid (martyr).
Two raka'at salaat performed by a pregnant woman is better than 80 raka'at salaat performed by a non-pregnant woman.
A woman who is pregnant gets the reward of fasting during the day and of doing ibaadah (worship) during the nights.
A woman who gives birth gets the reward of 70 years of salaat (prayer) and fasting. For each vein that feels pain, Allah SWT gives her the reward of one accepted hajj (Pilgrimage to Makkah).
If the woman dies within 40 days of giving birth, she will die as a shahid (matyr).
(Hadith)......."A woman that dies in her virginity or during her pregnancy or at the time of birth or thereafter (in nifaas) will attain the rank of a martyr"
Nabi(salalaallahu alayhi wassallam) is reported to have also said ".......When her labour pains commence, the inhabitants of the earth and the sky are unaware of the stores of comfort that are prepared for her. When she delivers and breast feeds her child, then she will be granted a reward for every gulp of milk, if she had to remain awake during the night for the sake of the child, she will receive the reward of emancipating seventy slaves in the path of Allah Ta'ala. O Salaamat! Do you know who these women are? They are pious, upright, with a delicate nature yet obedient to their husbands and not ungrateful to them"
[Source: Madrasa In'aamiyyah]