Infections In Pregnancy

Definition
Periconceptual infection: when maternal infection occurs around time of fetal conception

First trimester infection: when maternal infection occurs from the last menstrual period up to 13 weeks of gestation

Second trimester: when maternal infection occurs between 14 to 27 weeks of gestation

Third trimester: when maternal infection occurs between 28 weeks gestation to delivery

Epidemiology
As compared to nonpregnant women, pregnant women are more susceptible to common infections such as influenza, urinary tract infections and less common infections such as Listeria (a foodborne bacteria) and malaria (a mosquito borne parasite).

There is evidence that women have increased disease severity when they have certain infections during pregnancy. Some notable examples are influenza, hepatitis E, pneumococcal pneumonia, chickenpox and gastroenteritis.

Why do women have more severe disease when they are infected during pregnancy?
Pregnancy has been thought to be an “altered immune state” although not an “immunocompromised state”

This has been attributed to hormonal and physical changes that occur during pregnancy. As pregnancy progresses, female hormone (such as estradiol, progesterone) levels increase steadily. These high hormonal levels result in immunosuppressive effects on the immune system. The interplay between sex hormones and immune system is complex and multifactorial. Many organs are thought to be affected by these changes. In general, the levels of inflammatory cytokines are reduced. The placenta is an active immunologic site and certain infections such as listeria and malaria have a “tropism” to the placenta.

Physical changes that occur include the enlarging uterus, decreased lung volume, urinary stasis and increased workload on the heart.

Impact of maternal infections on the fetus
One of the major concerns of infections during pregnancy is its impact on the growing and developing fetus. This may result in fetal distress with early labour and even fetal loss from miscarriage. It may also affect development of the fetus. Some of these nonchromosomal effects may be categorized as:

  • Neural tube defects
  • Limb reduction
  • Hydrocephalus
  • Congenital heart defects
  • Cleft lip
  • Gastrointestinal defects

Impact of untreated infections on mother
Untreated or undiagnosed infections in the mother can also result in adverse maternal outcome. The common example is urinary tract infections in pregnancy. If untreated or not fully treated, it can result in long term consequences for the mother – like future renal disease, renal damage, etc. Maternal infections and sepsis can impact on fetal development. In untreated, infections like tuberculosis – close contact during the nursing period will pose infectious risks to the newborn infant.

Clinical
Maternal infections: the patient may have typical complaints of fever, chills and symptoms focused to the site of infection. In asymptomatic infection, women are infected but do not have any significant symptoms. These infections are diagnosed only when they have antenatal screening blood tests.

Fetal infections may manifest as poor growth or growth abnormalities on routine ultrasound. Some fetal infections result in early labour, miscarriage (spontaneous abortion) and fetal loss.

Diagnosis
Diagnosis of maternal infections usually involves blood tests and specimen samples obtained from the site of infection. Interpretation of maternal serology and dating the time of infection is often difficult. Standard X-rays are avoided and ultrasonographic examinations (where appropriate) are usually used.

Diagnosis of fetal infections will involve ultrasound examination for anatomic damage and direct sampling from the fetus (amniotic fluid and/or fetal blood sampling).

Treatment and Management
Detailed treatment recommendations are beyond the scope of this short write up and must be individualized according to type of infection and the gestation period. Suffice to state that where there is an antimicrobial agent that can be administered safely in pregnancy, it should be instituted as soon as the diagnosis is apparent. Sometimes, these agents are administered for treatment of both mother and the fetus. If the fetal infection is confirmed by fetal sampling, therapeutic abortion is sometimes considered by the parents.

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