Introduction

Infections that are considered straightforward or harmless in everyday practice can be anything but in the pregnant patient. Some are more common than usual in pregnancy, while others become more dangerous. Certain infections may be asymptomatic for the mother, but can still traverse the placenta and affect the fetus. We begin with bacterial and parasitical infections in part 1 of this 2-part series.

Group B Streptococcus (GBS)

GBS is a major cause of chorioamnionitis and puerperal endometritis. It’s the leading cause of neonatal morbidity and mortality in North America. It colonizes the lower female tract and 5-30% of women are asymptomatic carriers. Vertical transmission rates are high, causing neonatal sepsis in 0.4% of live births, and the mortality rate associated with early onset disease may be as high as 50% due to prematurity. In the neonate, these infections can contribute markedly to chronic morbidity, including mental retardation and neurologic disabilities.

Current recommendation is for universal prenatal screening with a standard culture of the distal vagina and anorectum collected between the 35th-37th weeks. No prophylaxis is needed if the screening culture is negative. Patients whose cultures are positive or those with risk factors should receive intrapartum penicillin prophylaxis.

Gonorrhea (Neisseria gonorrhoeae)

Infection with N. gonorrhoeae during pregnancy can lead to endometritis, pelvic sepsis, ophthalmia neonatorum and systemic neonatal infection. Screening of all pregnant women in early pregnancy is recommended due to the adverse consequences of an untreated infection. Co-infection with Chlamydia trachomatis is very common, justifying treatment for both STIs when N. gonorrhoeae is diagnosed. All positive cases should be treated with cefixime, ceftriaxone or spectinomycin as an alternative. A test of cure is recommended in pregnant women.

Chlamydia trachomatis

Chlamydia trachomatis is a very common sexually transmitted pathogen. Infection during pregnancy can have serious maternal and neonatal consequences. Maternal infection is often asymptomatic but can be associated with postpartum endometritis, premature rupture of membranes and preterm delivery. Vertical transmission during delivery can cause conjunctivitis and pneumonitis in the newborn. National guidelines recommend screening for Chlamydia early in pregnancy. Women at continuing risk for STI acquisition should be re-screened in the third trimester. Current regimens for pregnant women include 7-day courses of erythromycin or amoxicillin, or alternatively azithromycin in a single dose.

Hyperemesis gravidarum and Helicobacter pylori infection

Most women experience nausea and vomiting of moderate intensity in pregnancy, but morning sickness usually subsides in the second trimester. In < 1% of pregnant women, these symptoms are of greater severity and frequency and can persist throughout gestation. This is hyperemesis gravidarum (HEG), which can significantly interfere with normal living and lead to weight loss, dehydration, electrolyte imbalance, ketonemia, ketonuria, and possible hepatic and renal damage in the mother. It can also adversely affect fetal growth and lead to preterm birth. The most severe forms of HEG sometimes force women to end their pregnancies.

Treatment is initially supportive, relying on the avoidance of foods associated with nausea. Antiemetic drugs may help women whose symptoms continue to worsen. Those that can’t be managed as outpatients can receive fluid and electrolyte replacement as well as supplemental nutrition.

Some research has linked Helicobacter pylori infection to HEG and adverse fetal outcome, but further investigation is needed. Meta-analysis of existing data has found that high heterogeneity between studies precludes a firm conclusion. But it does seem that women tend to present more severe sickness and vomiting in the presence of H. pylori infection.

It’s been suggested that H. pylori infection could cause intrauterine growth retardation or micronutrient deficiencies leading to neural tube defects in the fetus, but no significant association has yet been found. On the other hand, European researchers found that large amounts of specific IgG H. pylori antibodies may be transferred transplacentally from infected mothers to their neonates and that specific IgA antibodies may also be passed onto newborns through breast milk. Future research looking into nutritional status and immunocompetence may shed light on these contradictory situations.

The currently available evidence hasn’t yet allowed for the development of screening or treatment guidelines for H. pylori infection. While eradicating the bacteria may help prevent gastric cancer, treatment should only be prescribed in pregnancy if benefits outweigh the risk to the fetus.

Vulvovaginal candidiasis

Pregnancy predisposes patients to Candida infections but the infection doesn’t seem to be associated with adverse pregnancy outcomes, nor with vertical transmission. Both maternal breast candidiasis and infection of the newborn are common, however, in particular post-antibiotic therapy and further research is needed to better understand its control and prevention.

The diagnosis is mainly clinical and symptoms include pruritus, vulvovaginal erythema and a non-malodorous white curd-like discharge. The primary goal of therapy should be symptom control as Candida is often difficult to eradicate in pregnancy. Treatment for this group should be restricted to topical azoles such as butoconazole and clotrimazole.

Trichomoniasis (Trichomonas vaginalis)

Much remains unknown about trichomoniasis in pregnancy. It’s been consistently associated with poor pregnancy outcomes such as preterm birth, premature rupture of membranes and low birth weight. Awkwardly, the treatment for trichomoniasis, metronidazole, was itself associated with preterm birth in some early research. More recent studies suggest that metronidazole — but not clindamycin — can cut risk of preterm birth in trichomoniasis and bacterial vaginosis, if given in the first 20 weeks.

Current guidelines don’t mention either screening or treatment for trichomoniasis. Symptomatic patients diagnosed with the disease should nevertheless be treated, to ameliorate symptoms and to minimize the risk of sexual transmission. Diagnosis is usually performed by microscopy of vaginal secretions, though the method has low sensitivity. A combination of microscopy and culture is the most sensitive available test. Treatment of any sexual partner is essential for cure.

The recommended treatment for trichomoniasis consists of 2 g of metronidazole orally in a single dose; alternatively a 7-day regimen of metronidazole 500 mg may be prescribed. Unfortunately, there’s no alternative drug recommended for this disease. The decision of whether to treat or not must rest on a case-by-case assessment of risk and benefit.

Bacterial vaginosis

Bacterial vaginosis is characterized by an overgrowth of Gardnerella and other anaerobes often associated with increased malodorous discharge, without obvious vulvitis or vaginitis. It’s been associated with adverse outcomes in pregnancy such as premature rupture of membranes, preterm labour, preterm birth and postpartum endometritis. High-risk pregnancies (previous preterm labour/delivery or preterm rupture of membranes) should receive screening and treatment at 12-16 weeks. The diagnosis is based on the presence of a greyish discharge with a pH between 5.0-5.5, an amine-like odour with the alkalinization (KOH 10%) of the discharge and the presence of “clue cells” in the vaginal smear. Again, the preferred treatment regimen is metronidazole, 500 mg orally twice daily for 7 days. Re-screening and re-treating may be advisable if symptoms persist after the initial treatment. Clindamycin at 300 mg for 7 days is an alternative regimen but the risk of pseudomembranous enterocolitis will have to be taken into account with this drug.

Pediculosis pubis (Pthirus pubis)

Pediculosis pubis is a parasitic infestation of the pubic area. It can be acquired by sexual transmission and is highly contagious — rate of transmission after a single sexual intercourse with an infected partner is 95%. It doesn’t seem associated with adverse pregnancy outcomes but all women diagnosed with lice should be screened for other STDs. In addition, some forms of lice treatment are contraindicated in pregnancy.

Patients complain of pruritus and presence of lice or nits in their pubic hair. Differential diagnosis is made with anogenital pruritus and eczema. Treatment consists of application of permethrin 1% cream, applied to the affected area and washed off after 10 minutes. Re-treatment may be necessary if the parasite is observed at the hair-skin junction. It’s important to treat sexual partners, close contacts and family members even if asymptomatic; personal clothing items and bedding should be washed and dried appropriately.

Toxoplasmosis

More than 90% of women who acquire a primary T. gondii infection during pregnancy are asymptomatic, and approximately 85% of children born having congenital toxoplasmosis don’t initially exhibit any signs of disease. But the parasite has the potential to cause significant long-term damage to infected progeny including chorioretinitis, hydrocephaly, microcephaly, intracranial calcification, and mental retardation. The later the maternal infection takes place, the greater the probability of transmission to the fetus (from < 5% in early in gestation to > 80% by the end of pregnancy). Conversely, the severity of congenital infection is greatest when it occurs during the first trimester. Toxoplasmosis is a preventable and treatable disease.

Primary prevention can be achieved by reminding pregnant women of the behavioural risks that could expose them to acquiring the parasite during gestation, which include ingestion of raw or under-cooked meat, or of water or food contaminated with oocysts. Infected cats are the primary host. The animals usually present no symptoms even during an acute infectious episode but can shed millions of oocysts in their feces each day. The acute infection usually lasts about three weeks. An oocyst, which is invisible to the naked eye, takes 1-21 days to mature and become infectious and may survive for more than a year in moist soil. Human infection may result from handling contaminated cat litters by inhaling oocysts.

Secondary prevention is achieved through serological screening during pregnancy. If infection occurs, an attempt can be made to decrease fetal infection with spiramycin. Prenatal diagnosis of congenital disease can be made by PCR of the amniotic fluid, and if infection is proven or suspected, treatment can be initiated for the fetus in utero.

Scabies

Scabies is caused by infestation with the mite Sarcoptes scabiei. It’s usually acquired by sleeping with or in the bedding of an infested individual or by other close contact. The predominant symptom is pruritus. Diagnosis is made clinically and can be confirmed by microscopic demonstration of the organism, ova or feces in a mounted specimen. Characteristic lesions may occur on the nipples, emphasizing the importance of treating pregnant women. Those patients should be treated with permethrin cream 5% applied to all affected areas of the body from the neck down and washed off after 8-14 hours. Both sexual and close personal or household contacts should be examined and treated.