You probably know you need to avoid certain foods during pregnancy. Alcohol is off limits, and most obstetricians recommend that you limit caffeine. Because of bacterial contamination, it's important to avoid undercooked or raw meats. Interestingly enough, however, some fully-cooked meats are also off-limits during pregnancy--specifically, those that contain nitrates.
Sodium nitrate and sodium nitrite are both salt compounds that have application as preservatives in meats. Because they're both oxidizing agents, meaning that they take electrons out of chemical bonds and cause molecules to break, they can destroy DNA and other critical molecules in bacteria. This inhibits bacterial growth, making both sodium salts excellent meat preservatives. Unfortunately, however, these preservatives also react with certain components of meat, producing potentially harmful compounds, especially to a developing baby.
Most of the health concern surrounding meat preservatives is actually centered around sodium nitrite rather than sodium nitrate. Unfortunately, however, your body can convert a small portion of sodium nitrate that you eat into sodium nitrite, meaning that sodium nitrate leads to the same problems as sodium nitrite. Nitrites, explain Drs. Mary Campbell and Shawn Farrell in their book "Biochemistry," can react with compounds called secondary amines to produce carcinogens, meaning cancer-causing agents.
The reaction of nitrates to form nitrites, and then of nitrites with secondary amines, is worrisome for the reason that meat is a rich source of secondary amines. Therefore, since nitrates occur most frequently in the diet as meat preservatives, when you eat nitrate-preserved meat, you're consuming all the ingredients you need to produce carcinogenic compounds. Explains Dr. Miriam Stoppard in her book "Conception, Pregnancy and Birth," carcinogens in your body can cause cancer in both you and--if you're pregnant--in your unborn child.
A branch of the U.S. Centers for Disease Control and Prevention, or CDC, called the Agency for Toxic Substances and Disease Registry notes that pregnant women are among the group most susceptible to the toxic effects of nitrates and nitrites. Studies done by the CDC with nitrate- and nitrite-contaminated drinking water suggest that nitrates can cross the placenta, affecting the unborn child in addition to affecting the mother.
Aside from their carcinogenic potential, nitrates represent a risk to pregnant moms and babies because of their potential for reacting with the protein hemoglobin that delivers oxygen from the lungs to the tissues. When nitrates become nitrites and react with hemoglobin, they produce modified proteins called methemoglobins, explains the CDC. These don't deliver oxygen as effectively, which is of particular concern if you're pregnant, since your baby depends upon your hemoglobin to deliver oxygen to the placenta.