Talk to Gynecologist on Gyne

Asalamu alekum.. i wana ask about my sister ... She was married and had two abnormal babies.. and there age were 9 to 10 months after birth. My sister had some test and doc said that i was due to cousion marriage. And she get divorced. Now she is happily married and concieved from two months allhumdulilah but her doc asked her for abortion due to there is a chance of abnormal child again. Is there any test which examine for abnormality before birth or not .. and what should she done.. kindly respone