Immunizations and pregnancy is a controversial topic. In general, we would not recommend a pregnant women get the Yellow Fever
shot. However, there is limited to no data to support this. I would recommend that you discuss this with your OB/GYN. He or she can further address you concerns.
In general, Yellow Fever is a relatively rare condition. That being said, it can cause significant problems, therefore we vaccinate against it in specific populations.
There are two types of vaccines (generally speaking) -- inactivated vaccines and live attenuated vaccines. In inactivated vaccines the injection is of a protein or part of the virus. Your body sees it, then develops antibodies against it. This is just a part of the virus and not the whole thing -- so it really causes minimal problems. On the other hand, a live attenuated vaccine is the real life virus -- simply altered so it is weaker and doesn't really cause the disease. In these cases there is a small risk of getting the virus syndrome. There is even a smaller risk of passing it through the placenta to a child. Regardless, because of the theoretical risk we recommend against it. Yellow fever is (unfortunately) a live attenuated virus. If you are asymptomatic and did not develop a yellow fever type syndrome -- it is very unlikely you had a burden of disease to pass it on.
It is very unlikely that you have effected the child. Regardless, close prenatal follow up with ultrasounds are important.
Please talk to your doctor
about this issue.