Infection and preterm labour
Infection can impact a pregnancy in two major ways, both with serious effects.
- After premature rupture of membranes (PROM), both a mother and her fetus are at risk of developing an infection, which can cause serious illness, disability, or death. For preterm PROM (pPROM):1
- Antibiotics are given in an attempt to prevent infection and prolong the pregnancy.
- Before 34 weeks of pregnancy, antenatal corticosteroids are given to the mother to help develop the fetus's lungs.
- Bacterial infection that spreads to the uterus and amniotic fluid is a major cause of preterm labour.2 (Viral infection is rarely involved in preterm labour.3) Uterine infection triggers the release of substances that make the uterus contract and can cause the amniotic sac to rupture (PROM). Either or both of these events will start preterm labour. Infection can begin:
- In the vagina, such as bacterial vaginosis (BV), often without symptoms. Studies show that in most cases of preterm labour caused by infection, the bacteria found in the uterus came from the vagina.3
- In the urinary tract. A urinary tract infection can lead to serious kidney infection and endanger both a mother and her fetus.
- After amniocentesis or cervical cerclage is performed (this is very rare).1
- Through the mother's bloodstream (this is rare).3
Antibiotic treatment of infection and preterm labour
Antibiotics are recommended for specific problems in pregnancy, some of which may cause preterm labour.
- Urinary tract infection (UTI). All women are screened for UTI at their first prenatal visit. Antibiotic treatment is recommended for UTI, regardless of whether a pregnant woman has symptoms.
- Bacterial vaginosis (BV). Bacterial vaginosis is usually diagnosed when it causes symptoms, usually a bad-smelling vaginal discharge. Antibiotic medication can be used to correct an overgrowth of problem bacteria in the vagina. BV infection during pregnancy has been linked to a higher risk of preterm birth. Although treatment doesn't seem to prevent preterm birth, it does lower your baby's risk of low birth weight and your risk of premature rupture of membranes.4 Your doctor or registered midwife will use antibiotics for BV if you have symptoms.
- Preterm labour with pPROM. Antibiotic treatment is recommended for women with pPROM, as it prolongs pregnancy and reduces the risk of maternal and newborn infection.1
- Preterm labour without pPROM. Antibiotics do not seem to stop preterm labour or prevent complications in women with preterm labour, intact membranes, and no evidence of infection.5
- Group B streptococcus infection.Group B strep are a type of bacteria that can cause a severe infection in newborns. Women with PROM are screened for group B strep, as are all women at 35 to 37 weeks of pregnancy. If a mother tests positive, she is treated with antibiotics during labour in an attempt to prevent infection in her newborn.
| Author: | Kathe Gallagher, MSW Carrie Henley | Last Updated: April 10, 2007 |
| Medical Review: | Joy Melnikow, MD, MPH - Family Medicine Anne C. Poinier, MD - Internal Medicine Gregory A L Davies, MD, FRCSC, FACOG - Maternal-Fetal Medicine William Gilbert, MD - Perinatology | |
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