Actually, misscarriage is not the most predictible and realistic outcome...
If you think about it properly, for the last 4-5 episodes mangaka has never shown any episodes with Suzuka's father on them, apparently it is made to make reader forget about his existence to, once again, create an unexpected frustration to the plans of the couple. After they decided to keep the child (which was really predictible) its more likely that Suzuka's father will force her to do abortion. Though misscarriage will be a possible outcome considering her body weight and age... But, I am quiet sure that there is completely no way that father would allow her to keep the baby.
You're right. We haven't seen Suzuka's dad. We will have too soon though, and Yamato will probably get pwned. But I don't know if he is as strict as we think he is....but, on the other hand, he may be stricter. We've only met him on 2 occasions.