Well you can fall pregnant with one overy and one Fallopian tube (sister-in-law fell pregnant after having an etopic pregnancy.
Cristina wants a career as a Cardio surgeon and she doesn't want to be a mother. But she is married now and she should include Owen in the decision to end the pregnancy. They are both doctors, Owen has said he would take time off to be at home for the baby and Cristina can still work. Cristina has to learn to compromise, parenting is team work.
So to answer the question.
It will be a life changing experience if she does decide to have this baby.