Aspartame is a sweetener used as a replacement for sugar in many foods because it is about 200 times sweeter than sugar; therefore, the quantity needed is a lot less. Many people have questioned the safety of aspartame, and many studies have been performed.
The Food and Drug Administration (FDA) has stated that aspartame is safe for the general public. The American Dietetic Association printed a report on sweeteners in July of 1993 stating the use of aspartame during pregnancy is safe. There are two concerns that come to my mind in regard to eating foods with aspartame while pregnant. One is PKU, or phenylketonuria. This is an inborn error of metabolism, where a person cannot properly metabolize phenylalanine. I don't believe this is an issue for you because you would know by now if you suffer from this metabolic disorder. My second concern is the fact that aspartame is used in foods instead of sugar in order to cut calories. It is advised to not feed children foods with aspartame because of their high caloric needs. During pregnancy, you also have high caloric needs. Hearing that you eat a low-calorie yogurt worries me that you may be watching your caloric intake a little too closely. I just want to advise you to make sure you are getting enough calories, and that about 30 percent of them come from fat. At your stage in pregnancy, you should probably be gaining about one pound per week if you were at a good weight for your height before pregnancy.
Aspartame is made up of two amino acids: aspartic acid and phenylalanine. Amino acids make up proteins. Don't be confused, though -- aspartame is not a protein. The chemical configuration of aspartame is different from that of a protein. When aspartame is digested, it is broken down into aspartic acid, phenyalanine and methanol, substances that can actually be found in "natural" foods. For example, the same substances can be found in milk, fruits and vegetables. Actually, many of these "natural" foods have higher amounts of aspartic acid, phenylalanine and methanol because aspartame is used in such small quantities. Some of the breakdown products may cross the placenta, but studies show that the amount is insignificant, and therefore, determined to be safe.
Eating foods with aspartame is a personal choice. Some people feel it is safe because the results of studies show that to be the case. Others choose not to eat foods with aspartame because of situations in the past where the government ruled that a food additive was safe and then did some more studies and changed their minds. The final decision is yours -- if your pregnancy is going all right and you feel good with your choice, then those are the most important things.