Strep B in pregnancy: when antibiotics are used

Group B streptococcus is a bacterium that can live in the bowel or vagina without causing illness. A positive swab does not mean you are unwell, and it does not mean your baby has an infection. The concern is exposure around birth, when a newborn has limited protection against serious infection.

Your maternity team may record the result and make a plan for intravenous antibiotics during labour. The medicine is intended to lower the baby’s exposure while they pass through the birth canal; it is not a treatment that permanently removes carriage.

Keep the result with your maternity notes and tell the team caring for you when labour starts or your waters break. Follow the plan you were given rather than waiting for symptoms. If you have a planned caesarean birth before labour and before your waters break, the antibiotic plan may be different, so discuss the details with your obstetric team.

Do not take leftover antibiotics or stop a prescribed course without advice. Ask which medicines are suitable if you have had an allergic reaction to an antibiotic, and tell clinicians about the reaction and what happened.

Contact your maternity unit promptly if your waters break, contractions begin, you develop a fever, or you feel suddenly unwell. Seek urgent help for breathing difficulty, faintness, confusion, severe abdominal pain, or heavy bleeding. After birth, urgent assessment is needed if your baby is difficult to wake, feeds poorly, has breathing trouble, feels unusually hot or cold, or changes colour.

Ask when antibiotics should start, how they will be given, what happens if labour is fast, and whether your allergy history changes the choice of medicine. You can also ask how the newborn team will observe your baby after birth.