There are many reasons to be a vegetarian. Some do it for religious reasons, some for environmental reasons, and some just don’t like the taste of meat.
Then there is the type of vegetarian that doesn’t eat meat because they believe that all animal life is as valuable as human life. For this breed of vegetarian, I believe it would be inconsistent to be against abortion and then eat fertilized chicken eggs.
That said, there are many people who call themselves pro-life, yet have had an abortion. Beliefs don’t necessarily map to behaviors. Most people are hypocritical, or at least inconsistent, in at least one aspect of their life.