As a mom-to-be, you'll want to steer clear of those foods that have been preserved with nitrates and nitrites, chemicals used in food preservation that (in high amounts) aren't good for a developing fetus.

Can nitrates cause birth defects?

Babies whose mothers take in nitrates through drinking water have an increased risk of experiencing cleft palate, spina bifida and other forms of birth defects according to a large study of children in Iowa and Texas.

What is bad about nitrites?

When the nitrites manufactured in our mouth are swallowed, one of the things that can happen is that they react in the strongly acidic environment of the stomach to form nitrosamines – some of which are carcinogenic and have been linked with bowel cancer.