If the situation had been the other way around, with the surrogate wanting to terminate the pregnancy (for example, due to hyperemesis or her mental health) but the biological parents didn't agree, do you think the surrogate should be forced to continue with the pregnancy?
Personally I don't agree with termination under any circumstances but putting that aside, I do think that the surrogate's rights over her own body trump any contract. Termination carries long-term risks to the woman's mental and physical health, so the thought of a legal battle to try and force any woman to have an abortion is horrific in my opinion.