Infectious diseases in pregnancy
The midwife’s responsibilities start with familiarity with which pathogens to consider and awareness of where to refer women. In the unwell woman, knowledge of symptoms as well as investigations that should be instigated at appointments are critical.
Non-pathogenic organisms are essential to health. They can be found in the large intestine, referred to as ‘gut flora’, synthesising vitamins and controlling pathogenic organisms. They can be found in the vagina, where lactobacilli cause the mucoid secretions to be slightly acidic thereby preventing the growth of pathogenic organisms. Pathogenic organisms are ones that affect the woman’s health and wellbeing. They could be viruses, bacteria, fungi, protozoa or worms. Pathogenic organisms enter the body by different routes: some will enter via the lungs (respiratory transmission, inhalation); by the gastrointestinal tract (ingestion); into the blood circulation via the skin (inoculation); or through mucosa in the throat or vagina (direct contact). The incubation period is the length of time between the organism entering the body and symptoms appearing.
The body has defences against the invasion of pathogens. Skin, sebum, (which contains antibacterial and antifungal properties), normal flora (non-pathogenic organisms) and mucous membranes prevent entry into the body. Ciliated epithelial cells waft unwanted material away. Saliva contains IgA and the stomach produces hydrochloric acid, which kills many swallowed pathogens. The lowered pH of the vaginal mucosa renders the environment hostile to pathogenic organisms.
The main defence against infection is the immune system. It produces phagocytic cells, enzymes and proteins that destroy pathogens.
There are various leucocytes (white blood cells) in the blood. B and T lymphocytes identify pathogens and mark them with a specific protein, indicating that cells with this protein need to be destroyed. Other leucocytes are neutrophils, monocytes, eosinophils and basophils. These are measured in haematological tests and identified by the levels and the ratio of each to the others. Bacterial or viral infections can be identified.
The immune system will, when identifying a specific pathogen, produce antibodies to that pathogen such that if it invades the body a second or subsequent time the antibodies are present to prevent illness occurring.
Physiological changes in the anatomy in pregnancy make women vulnerable. Gut motility is slower. The pH of the stomach is less acid, so ingested pathogens will not be destroyed so effectively. Non-pasteurised cheese would not cause a problem in the non-pregnant state but in pregnancy the gut may not be able to neutralise the bacteria. The pH of the vagina is changed and pathogens are more able to grow in this less hostile environment. There is a higher risk of infectious disease transmission.
In pregnancy, the maternal immune response is altered to permit tolerance of the semiallogeneic fetal–placental unit. This is achieved through the activity of uterine macrophages and regulatory T cells, and effectively protects the fetus from rejection by the maternal immune system. While the changes between T1 and T2 helper cells protect the fetus, this has implications for maternal protection from infection. The maternal immune response is not suppressed but is moderated to accommodate the fetus. This means that pregnant women have increased susceptibility to infections and may suffer more severe consequences if infected. For example, pregnant women with influenza have a higher risk of developing pneumonia. Maternal infection during pregnancy has been linked to an increased risk of brain disorders in the offspring, such as schizophrenia.
Table 3.1 lists some common infections and Box 3.1 indicates some signs of infectious disease in women. It is important to note where the rash is, where it started and were it spread to. The same applies if ulceration is present. These observations help with diagnosis.
The midwife should be aware of local or national outbreaks of infectious diseases and needs to be aware of how to prevent the spread of an infectious condition.
At every visit check whether the woman has travelled or lived in a high-risk area. If the woman has a rash, it is advisable that she separated from other pregnant women.
Give advice regarding the prevention or spread of infection. Demonstrate and maintain good practice such as hand washing, wearing of gloves where appropriate and use of Standard Precautions. The midwife should liaise with the infection control specialist nurse in the hospital.
The midwife must screen the woman appropriately. This may mean taking blood or urine samples. The results must be obtained and followed up.
If a positive diagnosis is made, the woman may now be considered to have a high-risk pregnancy so more frequent antenatal checks are required. Obstetric input together with skills from the virologist, fetal medicine specialist, neonatologist and GP are required. The woman (and partner) need to be informed of the risks of suspected or diagnosed infections.
A multidisciplinary meeting should be convened to discuss management of the woman and baby.
The midwife should remain up to date on diagnosis and vaccines that are becoming available. Postnatally the woman can be vaccinated against some infectious diseases but the midwife must check the suitability of vaccines if the woman is breastfeeding.