The BLUES study is a type of research called a randomized control trial (RCT) and comprehensive cohort study. You may choose which of these of you wish to be a part of.
A RCT is type of research where volunteers have an equal chance of being in one of two groups a test group or a control group. The test group will get the BLUES Study as well as regular prenatal care. The control group will get only regular prenatal care. The decision for which group you are placed in is made by a computer, not BLUES staff, and is much like a coin toss. You have about equal odds of being either group.
If you choose not to take part in the RCT then you can still take part in the comprehensive cohort section of the study. You can choose to be a control (regular prenatal care) or a test subject (BLUES study as well as regular prenatal care).