Go to the Family tab and pull up the family. This will take you to the Family Home page. If you are on the Guardian, you can click on "Family Home" on the left. Under the Children Entered, click on "Add Prenatal Child".
Enter the information for that baby. For the name, you can put in "Baby" for the first name and then the last name. The sex will always be "Prenatal" even if the parents know the sex of the baby.
Enrollment Info - If the prenatal baby has the same enrollment date as the family by clicking the blue "use same date as family". If the prenatal enrolled after, then enter the date that the prenatal visits began.
Once the baby is born, you will click "Enter birth info" from the Family Home to update the DOB, sex and name.