INFECTIONS IN PREGNANT WOMEN Role of Diagnostic Microbiology
INFECTIONS IN PREGNANT WOMEN
Role of Diagnostic Microbiology
Dr. T.V.RAO M.D
Pregnancy is a dynamic state of health and disease, shared by the pregnant woman and a growing
fetus, a concern to the treating physician for timely diagnosis and necessary interventions. Infections
with Viral, Bacterial, Parasitic and Fungi do occur in any pregnant woman like other non-pregnant
woman of similar age. Most infections are not serious. But some infections are more important in
pregnant woman than in non-pregnant woman because of the potential for vertical transmission to
foetus or infant. There is a growing awareness on HIV, HBV, CMV, Rubella and Toxoplasmosis, on
rare occasions Varicella and Listeriosis can do harm to the growing foetus. With advances in medical
treatments and laboratory technologies we are more concerned with transmission of HIV, and HBV
as we can still interfere with appropriate treatments. Now it is certain, every pregnant woman needs
a successful screening for Rubella IgG, HBV surface antigen, and HIV antibodies apart from existing
protocol for screening for Syphilis in all pregnant women with VDRL / RPR testing.
WHY GOOD CLINICAL MICROBIOLOGY SERVICES ARE IMPORTANT
No laboratory test for diagnosing a specific disease should be undertaken on a casual testing basis
without knowing the implication of a positive value of test. Women are more willing to accept
routinely offered testing as in screening for syphilis with. The situations to screen for antibodies to
HIV turn to be entirely different and needs an informed consent, as every woman has a right to
refuse any medical investigation or treatments.
UNDERSTANDING MICROBIOLOGY REPORTS WITH IMPLICATIONS ON FETAL HEALTH
There is an unlimited gap of understanding between the laboratory reports and the treating
physician, which should be always brought down for improving our quality of services.
1. All requests for any particular serological or molecular testing should be based on clinical
symptoms (May not necessary as in HIV, HBV, CMV and Syphilis which are symptom free in early
2. Writing a good clinical history will certainly guide the testing clinical microbiologist to use the right
protocol in the laboratory methods.eg. Toxoplasmosis, CMV, Rubella to determine the active
INTERPRETATION OF RESULTS RUBELLA, CMV, TOXOPLASMOSIS, VARICELLA Infections.
1. Clinicians should request for IgG in all cases apart from IgM which is only positive in recent
2. Best serological evidence of recent infections is IgG seroconversion (a change from a negative test
to positive test) to understand all serological tests which turn out to be negative on first testing, do
not exclude recent infections. Testing should be repeated up to three weeks after suspected contact,
which may be extended up to 6 months in cases of diagnosis of HIV Infection for appearance of
3. When a specific IgM is positive without IgG being positive results should be interpreted with
caution. If Ig G seroconversion do not occur the IgM result is likely to be a false positive
4. The question comes how recent is infection: can be clarified with newer generation of serological
testing in accredited laboratories. The clinicians should ask for IgG avidity assays which will help
confirm or exclude recent infection. (Eg, Toxoplasmosis, Rubella and CMV) As high avidity indicates
that infection occurred several months previously. Interpretation depends on laboratory protocols
and should be discussed with clinical microbiologists.
HIV SCREENING OR TESTING
The problems of screening all pregnant women for HIV antibody is a complex issue. It should be
discussed and issue can be still be resolved if offered as testing with motive of offering antiretroviral
therapy to both mother and new born if infected.
SCREENING FOR SYPHILIS (WITH VDRL/RPR)
A routine test done in every pregnant woman irrespective of consent is associated with biological
false positives. Every positive test should be reconfirmed testing with TPHA, a specific test to detect
active infection. Testing with FTAbs IgG remains the best option before diagnosis of syphilis is ruled
BACTERIAL INFECTIONS IN PREGNANT WOMEN
Many bacterial infections have Major effect on women’s health with implications on the New born.
URINARY TRACT INFECTIONS
Urinary tract infections remain the most common infections at any stage of pregnancy. Many
present with asymptomatic infections, Asymptomatic bactenuria which can only be identified on
culturing the urine. It is ideal to order culturing in early pregnancy to be followed up to the last
trimester of pregnancy. Most neglected part of urine culturing remains with proper collection of
specimen and often left to an inexperienced nursing staff. The treating physicians should instruct the
staff how to collect a mid-stream and a clean catch sample. Less experienced Microbiologists give
confusing reports but should not forget to specify the validity of report. A cut off point of 100,000
bacteria/ml is the minimal criteria in healthy pregnant women with isolation of a single species e.g.
E.coli, Klebsiella species will strengthen the diagnosis of urinary tract infections. Missing of
asymptomatic Bacteriuria can cause premature labour and pyelonephritis in pregnant women.
GROUP-B STREPTOCOCCAL INFECTION
There is a growing awareness on infections with Group B Streptococci. CDC advices culturing for
Streptococcus B group at 35-37 weeks of pregnancy is important which can help to prevent early
neonatal infection particularly premature labour. Appropriate collection of specimen from cervix
remains the minimal requirement.
GONOCOCCAL AND CHLAMYDIAL INFECTION
They need specific or specialized techniques for precise diagnosis but only ordered in high risk group
of women as they can lead to pelvic inflammatory diseases. The physician should discuss with clinical
microbiologist as routine testing is not possible in less equipped laboratories and will not serve the
BACTERIAL VAGINOSIS AND CANDIDIAL INFECTIONS
There is a growing incidence of Gardernella Vaginalis and Candidial infection. Few laboratories have
adequate facilities for characterization of etiological agents. The clinical requests should specify
what they are looking for.
Today we have an ever growing list of microbes including Varicella, Herpes simplex, Parvovirus B19,
Listeriosis and many others encroaching on pregnant women. An appropriate investigation and
management can reduce adverse outcome, unnecessary interventions and anxiety. The need of the
hour in up gradation of our Microbiology laboratories to cope, with changing trends in infection as
there is ever-increasing list of Microbes harming a pregnant women and the growing foetus.
CAUTION ON MOLECULAR METHODS
All molecular methods for diagnosis of infectious diseases ordered with caution. It is ideal to try all
time tested laboratory methods and to consider the using of molecular methods which on many
occasions are research or academic tools with good number of false positive reactions.
In spite of several advances in Laboratory Technologies in Developing countries, we in India must
depend on the wisdom of our Physicians, as our patients do not afford many investigations on
random basis or for Academic interest. However, antenatal screening that is not based on accepted
criteria or well defined plan of action can cause unnecessary anxiety and potentially dangerous
intervention. Still we know little how a Fetus protects and survives itself in spite of several
challenges apart from Infection.
Dr.T.V.Rao MD Professor of Microbiology Freelance writer