Bacterial Infections in Pregnancy

Abstract

Certain infections, such as UTI, may have an increased incidence during pregnancy owing to physiological changes. Between 2 and 10% of pregnant women have covert or asymptomatic bacteriuria which is associated with an increased incidence of acute symptomatic UTI in later pregnancy if left untreated. Thus antenatal screening to detect the presence of bacteriuria is justified. Most women will remain abacteriuric throughout the remainder of pregnancy after a single course of antibiotic therapy but a small percentage will fail to respond or have recurrent UTIs.

Maternal infection with certain organisms, namely those which resist phagocytosis, may result in transplacental infection of the fetus in utero. Congenital syphilis is preventable and antenatal serological screening is usually routinely performed. Listeriosis following maternal infection in pregnancy is less predictable and the epidemiology of L. monocytogenes remains unclear. Genital tract carriage of sexually transmitted organisms, such as N. gonorrhoeae or C. trachomatis, may also be detected during pregnancy and antibiotic therapy will be indicated to eradicate such organisms and prevent maternal and neonatal morbidity. Antibiotic therapy during pregnancy will not, however, eradicate carriage of GBS from the genital tract, although carriage status at term can now be reliably predicted by using enriched culture techniques and swabbing multiple sites on more than one occasion. Where carriage is confirmed, the administration of intrapartum antibiotics to the mother appears a useful approach in the prevention of early onset neonatal GBS disease. Broad spectrum intrapartum antibiotics may also be indicated when there are complications, such as prolonged labour or premature rupture of membranes, which are associated with a higher incidence of maternal postpartum endometritis and morbidity than in women following uncomplicated vaginal delivery. Serious postnatal sepsis and shock is fortunately now rare.

The pharmacokinetics of antibiotics in late pregnancy and the puerperium are altered and maternal serum levels may be reduced by 10–50%. Most antibiotics cross the placenta and are excreted in breast milk. Some agents, such as the beta-lactams, are considered safe in pregnancy and breast-feeding women while other antibiotics are contraindicated owing to risk of toxicity (often rare) or teratogenicity (often theoretical). Caution is necessary with many agents which may cause side effects or toxicity although this does not necessarily contraindicate their use in pregnancy. As with any therapy, antibiotic administration should not be undertaken without due consideration of the toxic potential of the agent used. The benefits of therapy should always outweigh the risks.