Infections in pregnancy

Published on 09/03/2015 by admin

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Last modified 09/03/2015

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Chapter 30 Infections in pregnancy

Michael Flynn

Urinary tract infection

Asymptomatic bacteriuria

• Incidence is 2%–10% in pregnancy. This is similar prevalence to non-pregnant women.
• If untreated, 15%–45% will develop symptomatic infection.
• Treatment can prevent 70%–80% of urinary tract infections and pyelonephritis.
• Diagnosis: a single voided specimen urine culture can detect 80% of asymptomatic carriers.
• About 75%–90% of urinary tract infections in pregnancy are due to Escherichia coli.
• Treatment: amoxycillin or cephalosporin are safe in pregnancy.
• Prevention: screening mid-stream urine (MSU) is performed as first-visit screen.
• Bacteriuria is associated with increased risk of preterm birth, low birth weight and increased perinatal mortality, and treatment has been shown to decrease these risks.

Acute symptomatic urinary tract infection

• Acute cystitis occurs in about 1% of pregnancies, especially in the second trimester. Pyelonephritis occurs in 1%–2% of pregnancies, in which 7% of women will suffer from bacteraemia and 1% septic shock.
• Possible reasons for increased pyelonephritis in pregnancy include anatomic changes to the urinary tract, and possible immunosuppression.

Management

• Rehydrate.
• Diagnose from MSU specimens and blood cultures.
• Antibiotics are given intravenously if the patient is systemically unwell.
• Lower temperature (paracetamol).
• Assess the fetus.
• There is a recurrence of 10%–15%; therefore, test urine regularly.

Relapses and reinfection

• Relapse means recurrence of infection by the same organism, and reinfection is due to a different strain of bacteria after successful eradication.
• Relapse or reinfection occurs in 10%–15% of treated urinary tract infections.

Management

• Treat the current infection.
• Prophylaxis uses oral nitrofurantoin 50 mg daily or cephalothin 500 mg daily for duration of pregnancy.
• Intravenous pyelogram is required after delivery.

Syphilis

Incidence. Incidence in Australia is 2 in 1000.

Screening

• This should be performed with a specific Treponena pallidum assay (e.g. T. pallidum haemagglutination assay (TPHA) or T. pallidum particle assay or syphilis enzyme immunoassay (EIA)).
• Syphilis may be transmitted to the fetus in the second trimester, with the following consequences:

• premature delivery in 20%
• intrauterine fetal death (IUFD) in 20%
• subclinical infection in 20%
• congenital infection in 40%

Clinical syndromes

Primary syphilis

• Incubation period is 10–90 days with an average of 21 days.
• It presents as a painless genital sore; then in the third to sixth week lymphadenopathy occurs, and serology is positive in 25% of cases.

Secondary syphilis

• Bilateral symmetrical papulosquamous eruption appears 2 weeks to 6 months after primary lesion. T. pallidum is present in lymph nodes and condyloma lata.

Latent syphilis

• This covers early syphilis (duration <4 years) and late syphilis (duration >4 years). It is non-infectious except in pregnancy.

Tertiary syphilis

• Neurological and vascular lesions are present.

In pregnancy, the fetus is ‘safe’ under 18 weeks gestation because it cannot mount an immunological attack and cause tissue damage and inflammation. Congenital syphilis is associated with intrauterine growth restriction (IUGR), café-au-lait spots, bullous rash, saddle nose, nasal congestion, hepatosplenomegaly, notched teeth, osteochronditis and corneal scarring. Congenital syphilis may also be asymptomatic.

Management of syphilis

• Early syphilis (primary, secondary or latent of <12 months): treat with benzathine penicillin 2.4 million units intramuscularly weekly for 2 weeks, or erythromycin 500 mg four times a day for 15 days.
• Late syphilis (incubation >12 months): treat with intramuscular benzathine penicillin 2.4 million units weekly for 3 weeks, or erythromycin 500 mg four times a day for 30 days.
• Check for other sexually transmitted diseases, and treat the partner.

Toxoplasmosis

• Toxoplasma gondii is an obligate intracellular organism. The birth prevalence is 0.23 in 1000 births to non-immune mothers. The rate of maternal infection is 1.6 in 1000.
• The risk of transmission rises with increasing gestational age. However, the fetus is more severely affected if infected before 20 weeks gestation, and is usually asymptomatic if infected in the third trimester.
• Congenital toxoplasmosis can result in microcephalus, hydrocephalus, seizures, reduced intellect, chorioretinitis, cataract, hepatitis and pneumonitis.
• Primary infection is rare in pregnancy in Australia.
• Selective testing is recommended only for those women at increased risk and, preferentially, this testing is prior to pregnancy. Symptoms of acute toxoplasmosis include malaise, fever and cervical lymphadenopathy.
• Immunoglobulin M (IgM) is not a reliable marker of recent infection.
• If IgG-positive and IgM-positive and symptoms suggestive of infection, then repeat and check IgG titres and IgG avidity (suggestive of infection within 3 months).
• If the above is suggestive of recent acute maternal toxoplasmosis, then treatment depends on gestational age.
• Consider treatment with sulfadoxine and pyrimethamine and folic acid or spiramycin.
• Ultrasound and amniocentesis help with diagnosis.

Rubella

• The incubation period is 14–21 days; then a rash develops which lasts 2–7 days.
• Fewer than 5% of women are not immune to rubella at antenatal clinic screening.

Possible outcomes of maternal rubella infection

• no effect on the fetus
• placental infection only
• placental/fetal infection causing asymptomatic infection but affecting organs
• death of fetus (abortion, IUFD)
• congenital rubella syndrome (bilateral cataracts, IUGR, congenital heart disease, especially patent ductus arteriosus, sensorineural deafness and microphthalmia)

Risk to fetus of maternal infection

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