When to withdraw/is this professor being reasonable? I am currently in a difficult science class that is important for my major.  I have a current GPA of 3.5 that I am very focused on keeping. This semester I had a vacation out of the country that I had been planning for years. I spoke to all my professors about it and only one had any problem with my being unable to make two classes. This professor said that I would be unable to make up any of the class work and would receive a zero in all assignments given during the time I was gone, nor will I be allowed any extra credit to make up for the missed class work. As a result I worked extremely hard at keeping the highest grade possible in the class and when I left on vacation my grade was 97%. After I got back I found out I was pregnant. Sadly there were complications and I was hospitalized and had a miscarriage barely a week later. This caused me to miss an additional class. Though I spoke with the difficult professor about what was going on and offered to provide any documentation required my grade has been dropped to 77%. If my GPA drops too much I will lose my scholarship money and internship opportunities.  I have time to withdraw but I really don't want to waste the time and money. I have never had a professor treat me like this before, is this normal? I would like to hear some educated opinions.
In the US, it is up to the professor on how he/she wants to handle a student missing class without a valid excuse. Vacations are not valid excuses (doesn't matter how long you've been planning it, and why would it?).

However, medical issues are a valid excuse and the university usually has a policy on how to handle it, which professors have to adhere to. I would recommend talking to your advisor or the chair of the department about this. 

As @ChrisPhan mentioned, this particular situations looks to be protected by Title IX in the US. Most universities have staff known as Title IX Coordinators that you can contact. I imagine that they will take this very seriously.