Answer and explanation:
After some research, I can make up a conclusion and stablish that obese women have less of a tendency than average BMI females on taking folic acid supplementation, and the main reason for this fact is that there is a large number of overweight women who happen to have unexpected pregnancies because of hormonal contracpetion going wrong.
So birth defects (like neural tube defects) are one of the many problems that an obese woman can have during her pregnancy. This is why it's important to always have a balanced diet, but even more during this life stage.