INFECTIONS IN PREGNANT WOMEN, ROLE OF DIAGNOSTIC MICROBIOLOGY
Dr.T.V.Rao MDPregnancy is a dynamic state of health and disease, shared by the pregnant woman
and a growing foetus, 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 IgM, HBV surface antigen for HBV,
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, and made to accept the testing for HBV and
HIV with concerns on the growing foetus. 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 sero conversion (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 IgG 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 IgM IgG remains the best option before diagnosis of syphilis is
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 bactinuria which can only be identified on
culturing the urine. It is ideal to order culturing in early pregnancy in the first Trimester 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 bacteraemia can cause premature labour and pyelonephritis in
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 Gardnernella vaginitis and Candida 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 infection 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 up with changing trends in
infection as there is ever-increasing list of Microbes harming a pregnant women and the growing
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 Foetus protects and survives itself in spite of several
challenges apart from Infections.
NOTE -The role of a competent Clinical Microbiologist and rationalistic Physician are boon to
prevent theunnecessary Medication with false positive tests which are not mere harm to the
pregnant women but with greater dangers to the growing foetus. All the new generation of Medical
Microbiologists should be familiar with interpretation of different diagnostic tests with advances in
the Laboratory technology, and no single test should be taken as final and the pregnant women
should not be subjected to termination of Pregnancy and unsafe medications.
Dr.T.V.Rao MD Professor of Microbiology Freelance writer