Project – Prevalence of Asymptomatic Bacteriuria Among Pregnant Women. A Study of Antenatal clinic attendees at Imo State Specialist Hospital, Owerri, Imo State

CHAPTER ONE

INTRODUCTION

1.1 Background to the Study

Pregnancy is a physiological condition associated with anatomical, hormonal, and functional changes that may influence a woman’s susceptibility to infections. Among the infections encountered during pregnancy, urinary tract infections (UTIs) are particularly important because they may occur without noticeable symptoms and can progress to more serious complications if not identified and appropriately managed. The urinary tract consists of the kidneys, ureters, bladder, and urethra, and bacterial infection may involve any of these structures. During pregnancy, increased progesterone levels relax smooth muscle in the urinary tract, while the enlarging uterus may exert pressure on the ureters and bladder. These changes can contribute to urinary stasis and facilitate bacterial multiplication. The American College of Obstetricians and Gynecologists (ACOG, 2023) identifies UTIs as common pregnancy complications and explains that the spectrum includes asymptomatic bacteriuria, acute cystitis, and pyelonephritis. Similarly, Nicolle et al. (2019) emphasise that asymptomatic bacteriuria requires particular attention in pregnancy because its detection and treatment can help reduce the risk of complications. Therefore, investigating asymptomatic bacteriuria among pregnant women attending antenatal clinics is important for maternal healthcare and the prevention of avoidable pregnancy-related morbidity.

Asymptomatic bacteriuria (ASB) refers to the presence of bacteria in urine at a specified quantitative level in an individual who has no signs or symptoms attributable to a urinary tract infection. Unlike symptomatic UTI, in which patients may experience painful urination, urinary frequency, urgency, or lower abdominal discomfort, ASB may remain undetected unless appropriate laboratory investigations are performed. For women without urinary catheters, the Infectious Diseases Society of America (IDSA) defines ASB using significant bacterial growth, conventionally at least \(10^5\) colony-forming units per millilitre (CFU/mL) in a voided urine specimen, without symptoms of UTI; confirmation of persistence in women may require two consecutive specimens (Nicolle et al., 2019). In routine antenatal practice, ACOG (2023) recommends screening pregnant patients with a urine culture early in prenatal care and identifies a colony count of at least \(10^5\) CFU/mL as clinically significant for treatment. These diagnostic principles are important because detecting bacteria in urine does not automatically establish clinically significant ASB, particularly where specimens are contaminated during collection. Consequently, prevalence studies must employ clearly stated diagnostic criteria and appropriate laboratory procedures to ensure that the reported occurrence of ASB is reliable.

The prevalence of asymptomatic bacteriuria among pregnant women varies across populations and healthcare settings because of differences in demographic characteristics, socioeconomic conditions, personal hygiene, previous urinary infections, parity, and access to antenatal services. The timing of screening, specimen collection procedures, laboratory methods, and diagnostic thresholds may also influence reported prevalence. ACOG (2023) estimates that ASB occurs in approximately 2–10% of pregnancies, although the actual proportion may differ between populations. In a systematic review and meta-analysis of studies from sub-Saharan Africa, Odongo et al. (2021) examined the prevalence and antimicrobial susceptibility of bacteria associated with ASB among pregnant women and demonstrated the importance of regional evidence in understanding this condition. Such variation means that prevalence figures obtained from one country, state, or hospital should not automatically be applied to another setting. For pregnant women attending Imo State Specialist Hospital, Owerri, a facility-specific assessment is therefore needed to determine the proportion of women with significant bacteriuria during the study period and to provide evidence that reflects the local antenatal population.

Several bacterial organisms may be responsible for asymptomatic bacteriuria during pregnancy, with Escherichia coli commonly identified as the predominant causative organism. Other organisms may include Klebsiella species, Proteus species, Enterococcus species, and certain staphylococci, although their distribution varies among populations and individual studies. E. coli can colonise the periurethral region and ascend through the urinary tract, while its adhesins and other virulence factors facilitate attachment to urinary tract tissues. The presence of these bacteria in urine may be clinically important because some infections can ascend to the kidneys, particularly in susceptible pregnant women. ACOG (2023) identifies E. coli as the most frequently isolated pathogen in pregnancy-associated UTIs, while Odongo et al. (2021) reported a range of bacterial organisms and varying antimicrobial susceptibility profiles in their review of ASB among pregnant women in sub-Saharan Africa. Identifying the bacterial organisms present in positive urine cultures is therefore useful for describing the microbiological profile of ASB and supporting appropriate clinical management.

The occurrence of asymptomatic bacteriuria during pregnancy may be influenced by both physiological changes and individual characteristics. Hormonal changes, dilation of the ureters, reduced urinary tract motility, and urinary stasis can facilitate bacterial persistence in the urinary system. Other potential factors investigated in the literature include maternal age, parity, previous UTI, diabetes, sickle cell trait, socioeconomic circumstances, and personal hygiene practices. However, the contribution of these factors may vary between populations, and their presence should not be interpreted as proof that a woman has bacteriuria. Nicolle et al. (2019) explain that the clinical importance of ASB depends on the population being assessed and that pregnancy is one of the principal circumstances in which screening and treatment are recommended. ACOG (2023) similarly highlights the physiological changes of pregnancy that increase susceptibility to urinary infection. Examining relevant maternal characteristics among antenatal attendees at Imo State Specialist Hospital may therefore help determine whether selected characteristics are associated with ASB in the study population.

Although asymptomatic bacteriuria does not produce the typical symptoms of urinary infection, its identification during pregnancy is clinically important because untreated bacteriuria may be associated with the development of symptomatic infection, particularly pyelonephritis. Pyelonephritis during pregnancy can result in serious maternal complications, including systemic infection, hospital admission, and respiratory complications, while urinary infections have also been associated with adverse pregnancy outcomes such as preterm delivery and low birth weight. The strength of evidence for individual outcomes varies, and findings from older studies may not fully reflect contemporary populations and treatment practices. Smaill and Vazquez (2019), in a Cochrane review, examined the effects of antibiotic treatment for ASB during pregnancy and reported evidence supporting treatment, particularly in relation to reducing pyelonephritis, while noting limitations in the underlying evidence. ACOG (2023) likewise concludes that screening for and treating ASB have been associated with a reduction in pyelonephritis during pregnancy. These findings underscore the importance of determining the prevalence of ASB among antenatal clinic attendees so that women with clinically significant bacteriuria can be identified and appropriately managed.

The detection of asymptomatic bacteriuria depends on appropriate screening and reliable laboratory diagnosis because affected pregnant women may have no symptoms to prompt investigation. Urine culture remains the recommended method for screening ASB during pregnancy, as routine dipstick testing alone is insufficiently sensitive for reliably detecting the condition. Proper specimen collection, timely transportation, culture, bacterial identification, and interpretation of colony counts are essential to minimise contamination and ensure accurate results. ACOG (2023) recommends a urine culture once early in prenatal care, while Nicolle et al. (2019) recommend screening for and treating ASB in pregnant women. Although these recommendations establish the importance of detection, the prevalence of ASB must still be determined within individual healthcare settings to understand the local burden. At Imo State Specialist Hospital, Owerri, a study of antenatal clinic attendees can provide evidence on the proportion of women with significant bacteriuria, the bacterial organisms recovered, and the possible relationship between ASB and selected maternal characteristics. Such information may support local antenatal screening practices, strengthen maternal health education, and contribute to the prevention of complications associated with urinary tract infections during pregnancy.

1.2 Statement of the Problem

Asymptomatic bacteriuria is an important clinical concern during pregnancy because bacterial growth in urine may occur without the usual symptoms of urinary tract infection. This absence of symptoms can make the condition difficult to identify through routine clinical observation alone. Pregnant women with undetected bacteriuria may remain unaware of the condition until further complications develop, including symptomatic urinary infection or pyelonephritis. ACOG (2023) identifies ASB as a recognised pregnancy-related urinary condition and recommends screening with urine culture early in prenatal care. Consequently, the absence of urinary symptoms among antenatal clinic attendees should not automatically be interpreted as evidence that their urine is free from clinically significant bacterial growth.

Another problem is the potential consequences of untreated asymptomatic bacteriuria for maternal health. Pregnancy-related physiological changes can facilitate bacterial persistence and upward spread within the urinary tract, increasing the risk of more serious infection in some women. Although the evidence concerning certain adverse pregnancy outcomes varies in quality, treatment of clinically significant ASB during pregnancy has traditionally been recommended to reduce the risk of pyelonephritis. Smaill and Vazquez (2019), in their Cochrane review, assessed evidence on antibiotic treatment of ASB in pregnancy and identified benefits associated with treatment, while also noting limitations in the available studies. The possibility of preventable complications reinforces the need to identify women with significant bacteriuria through appropriate antenatal screening and laboratory investigation.

Furthermore, the prevalence of asymptomatic bacteriuria varies among populations, making it inappropriate to rely exclusively on prevalence estimates obtained from other hospitals or geographical areas. Differences in maternal characteristics, socioeconomic circumstances, access to antenatal care, specimen collection procedures, and laboratory diagnostic methods may influence the findings of individual studies. Nicolle et al. (2019) emphasise the importance of applying appropriate diagnostic criteria when identifying ASB, while ACOG (2023) recommends urine culture as the preferred screening method during pregnancy. Therefore, prevalence estimates from other locations cannot automatically establish the burden of ASB among pregnant women attending Imo State Specialist Hospital, Owerri.

The specific problem addressed by this study is the need to establish the prevalence of asymptomatic bacteriuria among pregnant women attending the antenatal clinic at Imo State Specialist Hospital, Owerri, Imo State. Without study-specific laboratory evidence, the proportion of antenatal attendees with clinically significant bacteriuria, the bacterial organisms responsible, and the possible associations between ASB and selected maternal characteristics remain undetermined for the study population. This investigation will therefore use appropriate urine collection and culture procedures to determine the occurrence of ASB among eligible participants. The findings may provide local evidence to support antenatal screening, maternal health education, and appropriate clinical management. The study will not assume a particular prevalence rate before the laboratory results are obtained.

1.3 Aim and Objectives of the Study

1.3.1 Aim of the Study

The aim of this study is to determine the prevalence of asymptomatic bacteriuria among pregnant women attending the antenatal clinic at Imo State Specialist Hospital, Owerri, Imo State.

1.3.2 Specific Objectives

The specific objectives are to:

1. Determine the prevalence of asymptomatic bacteriuria among pregnant women attending the antenatal clinic at Imo State Specialist Hospital, Owerri.

2. Isolate and identify the bacterial organisms responsible for asymptomatic bacteriuria among the study participants.

3. Determine the antibiotic susceptibility patterns of bacterial isolates recovered from urine specimens of participants with significant bacteriuria.

4. Examine the association between asymptomatic bacteriuria and selected maternal characteristics, including age, parity, and gestational age.

1.4 Research Questions

The study will answer the following research questions:

1. What is the prevalence of asymptomatic bacteriuria among pregnant women attending the antenatal clinic at Imo State Specialist Hospital, Owerri?

2. Which bacterial organisms are isolated from urine specimens of pregnant women with asymptomatic bacteriuria?

3. What are the antibiotic susceptibility patterns of the bacterial isolates recovered from the study participants?

4. Is there a statistically significant association between asymptomatic bacteriuria and selected maternal characteristics, including age, parity, and gestational age?

1.5 Research Hypothesis

The following null hypothesis will guide the study:

H₀: There is no statistically significant association between selected maternal characteristics and the occurrence of asymptomatic bacteriuria among pregnant women attending the antenatal clinic at Imo State Specialist Hospital, Owerri, Imo State.

The hypothesis will be tested at the 0.05 level of significance using an appropriate statistical test based on the type and distribution of the data collected.

1.6 Significance of the Study

The findings of this study are expected to be beneficial to pregnant women, healthcare practitioners, hospital management, public health authorities, researchers, and students.

Pregnant women: The study may improve awareness of asymptomatic bacteriuria and the importance of appropriate antenatal investigations, even when urinary symptoms are absent. The findings may encourage timely attendance at antenatal clinics and adherence to treatment prescribed following a confirmed diagnosis. ACOG (2023) identifies the detection and treatment of ASB as important components of urinary tract infection management during pregnancy.

Healthcare practitioners: The findings may provide useful information on the prevalence and distribution of ASB among antenatal attendees, helping clinicians understand the local burden of the condition. The results may also support appropriate interpretation of urine culture findings and the selection of suitable antibiotics based on laboratory susceptibility results and pregnancy-specific treatment guidance (Nicolle et al., 2019).

Imo State Specialist Hospital, Owerri: The study may provide baseline information on the occurrence of ASB among pregnant women attending the hospital. The findings could support the review of antenatal screening practices, laboratory services, and maternal health education programmes.

Public health authorities: The findings may contribute local evidence to maternal and child health programmes in Imo State. The information may assist in identifying areas requiring additional awareness, screening, or clinical management interventions.

Researchers and students: The study may serve as a reference for future investigations into urinary tract infections during pregnancy, bacterial distribution, antimicrobial susceptibility, and maternal health outcomes. It may also provide a basis for comparing findings from different hospitals and communities.

1.7 Scope of the Study

The study focuses on the prevalence of asymptomatic bacteriuria among pregnant women attending the antenatal clinic at Imo State Specialist Hospital, Owerri, Imo State.

The geographical scope is limited to the specified hospital, while the study population comprises eligible pregnant women attending its antenatal clinic during the defined study period.

The laboratory component will involve the collection of urine specimens from consenting participants who do not report symptoms attributable to urinary tract infection, followed by appropriate urine culture, bacterial identification, and interpretation of colony counts. For a voided specimen, the study will apply the diagnostic criteria specified in the approved protocol, taking into account that persistent bacteriuria in women may require confirmation using a second specimen (Nicolle et al., 2019).

The study will also examine the susceptibility of identified bacterial isolates to selected antibiotics and investigate possible associations between ASB and maternal characteristics, including age, parity, and gestational age. It will not assume that all positive urine cultures represent clinically significant ASB without consideration of colony counts, specimen quality, and the possibility of contamination.

1.8 Limitations of the Study

The study may be limited by the number of pregnant women recruited, the duration of data collection, laboratory resources, and the willingness of eligible participants to provide urine specimens.

Another limitation may arise from specimen contamination during collection or transportation. Mixed bacterial growth may make it difficult to distinguish clinically significant bacteriuria from contamination, particularly when collection and laboratory procedures are not carefully controlled. Schneeberger et al. (2013) examined contamination rates associated with urine sampling methods in pregnant women, highlighting the importance of appropriate specimen collection and interpretation.

The study’s single-hospital setting may also limit the generalisability of its findings to all pregnant women in Owerri or Imo State. In addition, a cross-sectional study can estimate prevalence and assess associations but cannot establish that a particular maternal characteristic causes ASB.

These limitations will be addressed through appropriate recruitment procedures, clear participant eligibility criteria, standardised urine collection instructions, timely laboratory processing, and transparent reporting of the study findings.

1.9 Operational Definition of Terms

Prevalence: The proportion of eligible pregnant women examined during the study who meet the established diagnostic criteria for asymptomatic bacteriuria, expressed as a percentage.

Asymptomatic bacteriuria (ASB): The presence of significant bacterial growth in urine without symptoms attributable to urinary tract infection, according to the diagnostic criteria adopted for the study.

Pregnant women: Women with an ongoing pregnancy who attend the antenatal clinic at Imo State Specialist Hospital, Owerri, and satisfy the study’s eligibility criteria.

Antenatal clinic: A healthcare service providing assessment, monitoring, education, and other appropriate care to women during pregnancy.

Urine culture: A laboratory procedure used to grow and detect bacteria present in a urine specimen and determine their quantity.

Bacterial isolate: A bacterial organism recovered from a urine specimen and identified through appropriate laboratory procedures.

Colony-forming units per millilitre (CFU/mL): A measure used to estimate the number of viable bacterial units in a millilitre of urine.

Antibiotic susceptibility pattern: The observed response of a bacterial isolate to selected antibiotics, interpreted using recognised laboratory standards.

Maternal characteristics: Selected personal and pregnancy-related variables, such as age, parity, and gestational age, examined in relation to ASB.

Significant bacteriuria: Bacterial growth meeting the quantitative and interpretive criteria specified in the study protocol for clinically meaningful bacteriuria.

Project – Prevalence of Asymptomatic Bacteriuria Among Pregnant Women. A Study of Antenatal clinic attendees at Imo State Specialist Hospital, Owerri, Imo State