Annals of African Medicine

: 2013  |  Volume : 12  |  Issue : 3  |  Page : 160--164

Pattern of asymptomatic bacteriuria among pregnant women attending an antenatal clinic at a private health facility in Benin, South-South Nigeria

Aiyebelehin O Alfred1, Ike Chiedozie2, Duru U Martin3,  
1 Department of Family Medicine, Ahmadu Bello University Teaching Hospital, Zaria, Nigeria
2 Department of Public Health, Irrua Specialist Teaching Hospital, Irrua, Nigeria
3 Department of Medical Microbiology, Faith Mediplex, Benin City, Nigeria

Correspondence Address:
Aiyebelehin O Alfred
Department of Family Medicine, Ahmadu Bello University Teaching Hospital, Zaria


Background/Objective: The objective was to establish the characteristics of antenatal attendees in Faith Medical Centre, a private health facility in Benin City who have asymptomatic bacteriuria (ASB) as well as to determine the relationship between ASB and socioeconomic status. Methods: It was a descriptive, cross-sectional study involving 240 pregnant women who presented in the course of antenatal care from January to April 2009. With the aid of a questionnaire patients who were recruited for the study had their socio-demographic data and relevant gynecological and drug history recorded. A physical examination was done to document temperature, height, weight and symphysiofundal height. A clean-catch midstream urine sample was collected for microscopy and culture. White blood cell count of≥5/hpf and/or bacteria count of≥1/hpf of urine was considered significant for urine microscopy and a single colony count of ≥105/ml from two consecutive urine samples was considered significant for urine culture. Results: The prevalence of ASB was 13.8% by urine culture and 43.8% by urine microscopy among antenatal attendees in Faith Medical Centre, Benin City. There was no relationship between ASB and socio-economic factor (P value=0.1267). There was also no significant specific trend between ASB and age (P value=0.0578). Using urine culture as gold standard, the sensitivity of urine microscopy was 90.9%, the specificity was 49.3%, the positive predictive value was 22.2% and the negative predictive value was 97.1%. Conclusion: ASB in pregnancy is common in Faith Mediplex and has no statistically significant relationship with socioeconomic status. The current practice of diagnosing and treating ASB based on urine microscopy needs to be reviewed since the specificity of urine microscopy is very low. Also the practice of screening pregnant women only at the time of booking can lead to under-diagnosis of ASB. This is so because most women who develop this condition later in the course of antenatal care will be missed.DQ

How to cite this article:
Alfred AO, Chiedozie I, Martin DU. Pattern of asymptomatic bacteriuria among pregnant women attending an antenatal clinic at a private health facility in Benin, South-South Nigeria.Ann Afr Med 2013;12:160-164

How to cite this URL:
Alfred AO, Chiedozie I, Martin DU. Pattern of asymptomatic bacteriuria among pregnant women attending an antenatal clinic at a private health facility in Benin, South-South Nigeria. Ann Afr Med [serial online] 2013 [cited 2021 Jun 22 ];12:160-164
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The importance of ensuring that a woman attains the highest possible level of health cannot be overemphasized and much more so a pregnant woman as this goes a long way in determining the outcome of her pregnancy. The diagnosis and management of asymptomatic bacteriuria (ASB) is a very important aspect of antenatal care as it is consistent with general health promotion, specific protection, early diagnosis and treatment. Asymptomatic bacteriuria is a common bacterial infection of the urinary tract requiring medical treatment in pregnancy. Diagnosis and treatment of asymptomatic bacteriuria is important as approximately 20-40% of these women, if untreated during pregnancy, will develop a symptomatic urinary tract infection (UTI). [1] It is also in keeping with the goal of safe motherhood initiative; that women safely go through pregnancy and childbirth and produce healthy babies. Untreated asymptomatic bacteriuria is a risk factor for acute cystitis (40%) and pyelonephritis (25-30%) in pregnancy. [2]

Several studies have shown different prevalence rates of asymptomatic bacteriuria in pregnancy with quoted values ranging from 3-10% in most developed countries. [3] In most Asian countries and sub-Saharan Africa, including Nigeria, higher prevalence rates ranging from 5.6-26% are quoted. [4],[5] This variation in the prevalence of asymptomatic bacteriuria is explained by differences in the population characteristics, and most importantly, differences in screening methodology and criteria for the diagnosis of asymptomatic bacteriuria in these studies, which in most cases are at variance with the accepted standard.

The combination of mechanical, hormonal and physiologic changes during pregnancy contributes to significant changes in the urinary tract, which has a profound impact on the acquisition and natural history of bacteriuria during pregnancy. This includes dilatation of the ureter, decrease in ureteral peristalsis, and decrease in bladder tone. Glucosuria and an increase in levels of urine amino acids during pregnancy are additional factors. [1] Also, the physiologic increase in plasma volume during pregnancy decreases urine concentration and increases urinary progestins and estrogens, which may lead to a decreased ability of the lower urinary tract to resist invading bacteria. [6]

In many developing countries, financial constraints may restrict the feasibility of introducing general screening of all pregnant women. The high laboratory charges of urine culture make it less cost-effective for routine screening in populations that have a low prevalence of ASB. Facilities to culture bacteria from a midstream clean-catch urine sample in each trimester are still considered the best diagnostic test available in all settings. [7] Prior to this time, no study has been done in this environment to determine the pattern of asymptomatic bacteriuria of pregnancy. Studies done at various centers in Nigeria such as Abakaliki, [8] Ibadan, [4] Sokoto, [5] Enugu [9] and Ado-Ekiti [10] sought to establish only the prevalence and microbiological characteristics of asymptomatic bacteriuria of pregnancy. None of these studies established any relationship between asymptomatic bacteriuria of pregnancy and socioeconomic factors. Hence, the outcome of this study will result in strategies for better evaluation of this condition in this environment. In this study the null hypothesis is: there is no relationship between ASB and socioeconomic status. The alternative hypothesis is: there is a relationship between ASB and socioeconomic status.

 Materials and Methods

This cross-sectional study was carried out in the antenatal clinic of Faith Medical Centre Benin City, Nigeria from January 15 to April 14 2009. It was approved by the Ethical Committee of the hospital. All pregnant women attending theantenatal clinic during the study period and who consented to participate in the study by signing the consent form were clinically evaluated to exclude signs and symptoms of UTI. With the aid of a questionnaire, demographic features including age, parity, and gestational age of pregnancy were collected. The socioeconomic status of the participants was determined using Olusanya's model. [11] Socioeconomic index score was awarded to each patient based on her educational attainment and the occupation of her husband. Income is an important determinant of one's socioeconomic status. The family income is a derivative of both the woman's education and her husband's occupation. For occupation, a score of 1 was allocated to senior public servants, professionals, managers, large-scale traders, businessmen, and contractors, 2 to middle-level workers like teachers, artisans, small-scale traders, 3 to unskilled laborers and the unemployed. For educational level, a score of 0 was awarded to those with post-secondary education, 1 to those with post-primary and 2 to those with primary school education or less. From the above, a socioeconomic index score was obtained from the addition of the educational score and the occupational score levels which ranged from 1 to 5. An index of 1 and 2 was classified as upper socioeconomic class. A score of 3 was classified as middle class while scores of 4 and 5 were classified as lower class.

After being instructed on the correct mode of self-collection of urine sample and the importance of clean-catch urine, they were provided with sterile universal bottles. Samples of 10-15 ml urine were obtained. It was microscopically examined for pus cells and bacteria, and then cultured within two hours. Samples were cultured on dried plates of Blood agar and MacConkey agar for bacterial growth, using a calibrated loop delivering 0.002 ml of urine. Plating on Kligler Iron Agar as well as Gram staining and Coagulase test were used to achieve species differentiation. Plates were incubated aerobically at 37°C overnight. Colony counts yielding pure bacterial growth of 10 5 or more of bacteria per ml of voided urine aseptically collected from two consecutive samples were deemed significant. The Statistical Package for Social Sciences, Version 15.00 for Windows (SPSS-15) was used for data entry with appropriate coding and calculation of Probability values (P values) for the variables. Chi-square was used to evaluate the difference between proportion and categorical variables. Statistical level of significance was taken as 0.05 and 95% confidence interval (CI) was calculated.


Out of the 240 booked antenatal care patients in the study who were analyzed, 33 had significant bacteriuria giving a prevalence rate of 13.8%. The age range was from 20 years to 40 years with a mean age of 28.7±1. [Table 1], [Table 2], [Table 3] and [Table 4] show the age distribution, the parity distribution, the socioeconomic status and the educational status of the participants, respectively. The highest age group-specific prevalence rate of 24.1% was observed in the group of 35-39 years. Women with parity ≥4 had the highest prevalence rate of 15.4% while nulliparous women had the least prevalence of 12.3%. Women in the upper socioeconomic class had the least class-specific prevalence rate of 10.1% while those in the lower class had the highest class-specific prevalence rate of 22.7%. {Table 1}{Table 2}{Table 3}{Table 4}


This study showed that the overall prevalence of asymptomatic bacteriuria among pregnant women attending the antenatal clinic of Faith Mediplex was 13.8%, which is higher than the reported prevalence in most of the previous studies. In these studies the prevalence of asymptomatic bacteriuria in pregnancy varied from 4-7%. [12],[13] However, the prevalence in this study is lower than what has been reported in Ibadan [4] (21%) and India [14] (19%). It should be noted that the study done at Ibadan used a lower bacteriuric level of 10 3 cfu/ml. Lowering the significant bacteriuric level in a study involving urine culture is bound to increase the prevalence rate.

In the study, the 30-34 years' age group accounted for 39.2% of the total population, probably skewing the high prevalence to this group. This agrees with the study at Ibadan [4] and Washington [13] where there was no trend associated with age. While some researchers showed that the highest prevalence was in the younger age group, [6],[15] others showed that it is highest in the older age group. [12],[16] On the whole, age does not seem to have a consistent effect on the prevalence of ASB of pregnancy.

Literature revealed that there are various factors that are associated with asymptomatic bacteriuria during pregnancy. For example, some previous studies found that the incidence of asymptomatic bacteriuria is strongly associated with multiparity and during the third trimester. [17],[18],[19] Furthermore, demographic determinants such as illiteracy or being from a low socioeconomic background are also associated with asymptomatic bacteriuria during pregnancy. [19] In this study, such association was not identified between these characteristics and bacteriuria. A high proportion (57.9%) of the respondents in this study is in the upper socioeconomic class. Only 9.2% of the respondents are in the lower socioeconomic class. This is probably due to the fact that people in the lower social class are more likely to believe that it is cheaper to access healthcare in private clinics and maternity homes than in secondary and tertiary healthcare facilities like our study centre. They also have the tendency to use alternative care such as Traditional Birth Attendants (TBAs). Involvement in delivery conducted by untrained personnel in residential buildings and worship centers is also a common practice among this group.

From the study, the prevalence of ASB based on urine microscopy was 43.8%. Using urine culture as a gold standard, the sensitivity of urine microscopy was 90.9%, the specificity was 49.3%, the positive predictive value was 22.2% and the negative predictive value was 97.1%. The specificity of 49.3% is very low or it has a high false positive rate in that 51.7% of women without ASB will need confirmatory testing with urine culture. This suggests that urine microscopy is not a very good method for exclusion of ASB as the specificity is less than 90%. However, a negative predictive value of 97.1% means patients with negative test results are very unlikely to have the disease. These results are in agreement with the Turkish study [20] where the sensitivity and negative predictive values of leukocyturia as a screening test for asymptomatic bacteriuria were 91.3% and 98.5% respectively, but not with the work done in the United Arab Emirates where a sensitivity of 67% was obtained. [21]

In this study Staphylococcus aureus was the most frequently isolated pathogen n=18 (54.5%) closely followed by Escherichia coli n=14 (42.4%). This is similar to the findings in the studies done in Abakaliki [8] and Ado-Ekiti [5] but different from those done in Ghana, [15] Ethiopia, [22] Turkey [16] and Qatar [6] where Escherichia coli was the predominant uropathogen.

In conclusion, the prevalence of ASB in Faith Mediplex, Benin City by urine culture is high considering the fact that AFB is a form of urinary tract infection and as such can impact negatively on the outcome of pregnancy ASB has no statistically significant relationship with socioeconomic factors, parity or gestational age (P values>0.05). There is also no specific trend between age and the development of ASB. There is a low accuracy and positive predictive value of leukocyturia or simple urine microscopy in the diagnosis of ASB of pregnancy. The practice of diagnosing ASB by urine microscopy is, therefore, inadequate.


We wish to thank the nursing staff of Faith Medical Centre, Benin City for their help in patient recruitment as well as Dr. Olarenwaju Badaru for the statistical analysis.


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