- Group B Strep (GBS)
You will most likely be tested for Group B Strep at the end of your pregnancy. If you are positive for GBS during that test you will most like receive antibiotics in labor via your IV or saline lock. - Prophylactic - Just in Case
In some birth situation you may be given antibiotics just in case, an example might be for a cesarean section or c-section. - Preterm Labor
If you are in preterm labor, it may be caused by an infection. Using antibiotics may stop your labor or at least help with the infection. - Your Water Has Been Broken Over a Certain Period of Time
Typically antibiotics are given after 18 hours of your membranes being ruptured to try to prevent a uterine infection or chorioamnionitis, if your Group B Strep status is unknown. This may be sooner or later depending on your hospital or practitioner's protocol. - Running a Fever
If you are running a fever in labor, they may give you antibiotics, even before they know why you are running a fever to try to prevent transmission of whatever you have to the baby.
A Word About Mitral Valve Prolapse (MVP)
It used to be that if you had a mitral valve prolapse (MVP) you would be asked to do prophylactic antibiotics to prevent heart problems. It was also used in cases of rheumatic heart disease. This is no longer considered the protocol.
Source:
Obstetrics: Normal and Problem Pregnancies. Gabbe, S, Niebyl, J, Simpson, JL. Fifth Edition.




