1. Background
Urinary tract infections are a common health problem among women compared with men due to a short urethra, vaginal proximity, and facilitated entry of pathogens by sexual activity (1-4). Pregnant women are more susceptible to symptomatic and asymptomatic urinary tract infection due to their anatomical and physiological status and increased sex hormones during pregnancy.
Asymptomatic bacteriuria refers to the presence of more than 100,000 colony-forming units (CFU) of a type of pathogen per mL of urine in two successive samples from the middle of the urine flow or a catheterized specimen (5-7).
About 30% of untreated women with asymptomatic bacteriuria are prone to pyelonephritis during pregnancy (7), where the systemic febrile infections of the mother, including pyelonephritis, are associated with preterm labor and low birth weight (8, 9). Asymptomatic bacteriuria in pregnancy may lead to hypertension, preeclampsia, intra uterine growth restriction, low birth weight, postpartum endometritis, septicemia, and maternal death (8, 10, 11). With early screening during pregnancy, a relatively high prevalence of urinary tract infection, especially asymptomatic bacteriuria, can be prevented due to its significant complications (8).
A golden standard for screening asymptomatic bacteriuria from urine specimens is during 12-16 weeks of gestation age of pregnancy (12). The results of several studies have shown that preterm labor in pregnant women with asymptomatic bacteriuria is higher than other pregnant women.
2. Methods
This descriptive-analytic study was conducted to compare the asymtomatic bacteriuria of pregnant women with preterm labor and term in the first and second trimesters of pregnancy. All women who referred to the maternity clinic of Ali Ebn Abitaleb Hospital of Zahedan, urine samples were collected for bacteriuria examination in 2015 to 2016. In order to reduce the risk of contamination during collection, sampling was performed after hand washing and washing the genital area with normal saline impregnated cotton. In addition, about 20 mL urine samples from the median urinary flow of patients in a sterile container were collected. Samples were taken to the lab after collection and processed immediately after. Samples that had not been processed until this time were kept in the refrigerator at 4°C. For urine culture, 0.01 mL of urine sample was taken by calibrated loop and inoculated with culture media and methylene blue eosin. The environments were placed in a 37°C incubator for 24 hours. In the case of growth of more than or equal to 100,000 colonies per mL of urine in the culture medium, the sample was considered as an asymptomatic bacteriuria. In the analysis of information, descriptive statistics tables and chi-square test will be used. In the presentation of the results, the confidence interval will be 95% and there is a significant statistical difference less than 5%.
3. Results
In this study, the prevalence of asymptomatic bacteriuria was 33 (84.6%) in preterm labor and 6 (15.4%) in preterm labor. The prevalence of asymptomatic bacteriuria in women with preterm labor was significant. It was more than the group of women with preterm delivery and statistically significant difference was observed between the groups (P-value = 0.0001) (odds ratio = 7.38) (Table 1).
Table 1.Frequency of Asymptomatic Bacteriuria in Preterm and Term Pregnant
| Group/Variable | Term, Prevalence (%) | Preterm, Prevalence (%) | Total, Prevalence (%) | P-Value |
|---|---|---|---|---|
| Asymptomatic bacteriuria | 0.0001 | |||
| Positive | 6 (5.4) | 33 (29.5) | 39 (17.4) | |
| Negative | 106 (94.6) | 79 (70.5) | 185 (82.6) | |
| Total | 112 (100) | 112 (100) | 224 (100) | 0.0001 |
Parity in preterm pregnancy was not significantly different between two groups with asymptomatic bacteriuria and no asymptomatic bacteriuria (Table 2). In addition, in our study, there was no significant difference in the level of education between the two groups (P-value = 0.262) (Table 3). Parity in preterm delivery was not significantly different between two groups with asymptomatic bacteriuria and no asymptomatic bacteriuria (Table 4).
Table 2.Frequency of Parity in Term Pregnant Based on Bacteriuria
| Group/Variable | Patient with ASB, Prevalence (%) | Patient Without ASB, Prevalence (%) | Total, Prevalence (%) |
|---|---|---|---|
| Parity | |||
| PG | 2 (33.3) | 53 (50) | 55 (49.1) |
| 1 | 2 (33.3) | 30 (28.3) | 32 (28.6) |
| 2 | 1 (16.7) | 9 (8.5) | 10 (8.9) |
| 3 | 1 (16.7) | 7 (6.6) | 8 (7.1) |
| 4 | 0 (0) | 4 (3.8) | 4 (3.6) |
| 5 | 0 (0) | 2 (1.9) | 2 (1.8) |
| 6 | 0 (0) | 1 (0.9) | 1 (0.9) |
| Total | 6 (100) | 106 (100) | 112 (100) |
Table 3.Frequency of Education Among Two Groups (Term and Preterm)
| Group/Variable | Term, Prevalence (%) | Preterm, Prevalence (%) | Total, Prevalence (%) | P-Value |
|---|---|---|---|---|
| Study | 0.262 | |||
| Elementary (primary) | 41 (36.6) | 29 (25.9) | 70 (31.3) | |
| Guidance (secondary) | 32 (28.6) | 31 (27.7) | 63 (28.1) | |
| Graduate | 25 (22.3) | 32 (28.6) | 57 (25.4) | |
| Postgraduate | 14 (12.5) | 20 (17.9) | 34 (15.2) | |
| Total | 112 (100) | 112 (100) | 224 (100) | 0.262 |
Table 4.Frequency of Parity in Preterm Pregnant Based on Bacteriuria
| Group/Variable | Women with Bacteriuria, Prevalence (%) | Women Without Bacteriuria, Prevalence (%) | Total, Prevalence (%) |
|---|---|---|---|
| Parity | |||
| PG | 17 (51.2) | 42 (53.2) | 59 (52.7) |
| 1 | 9 (27.3) | 9 (11.4) | 18 (16.1) |
| 2 | 4 (12.1) | 16 (10.3) | 20 (17.9) |
| 3 | 2 (6.1) | 8 (10.1) | 10 (8.9) |
| 4 | 0 (0) | 3 (3.8) | 3 (7.2) |
| 5 | 1 (3) | 1 (1.3) | 2 (8.1) |
| Total | 33 (100) | 79 (100) | 112 (100) |
4. Discussion
Asymptomatic bacteriuria is more common in pregnant women than non-pregnant women. Although recurrent bacteriuria is more prevalent in pregnancy, the prevalence of pyelonephritis in pregnant women is higher than in the general population, which is probably due to physiological changes in the urethra in pregnancy (10, 13-15). Urinary tract infections begin in most pregnant women with presence of bacteria in the urine without any specific symptoms (16). It is estimated that 7 million cases of bladder infection are diagnosed in young women in the United States each year, which cost 1 billion dollars (6, 7).
Asymptomatic bacteriuria occurs in 2% to 7% of pregnant women depending on factors such as race and socio-economic status. The highest prevalence was in African-American women with sickle cell anemia and the lowest in white wealthy women (17, 18). It occurs precisely at the beginning of pregnancy, and almost one quarter of cases are detected in the second and third months, risk factors associated with most bacterial infections is the positive history of the previous urinary tract infection, pre-existing diabetes mellitus, parity, and low socioeconomic status (10, 13-15).
Without treatment, 30% - 40% of pregnant women with asymptomatic bacteriuria will have symptomatic urinary tract infections (including pyelonephritis) (17). If bacteriuria is eradicated, this risk is reduced by 70% to 80% (11, 19, 20), many studies have shown the association between urinary tract infection, especially asymptomatic bacteriuria, and poor outcome of pregnancy. Untreated bacteriuria is associated with an increased risk of preterm delivery, low birth weight, and prenatal mortality (16).
Urinary tract infection is a common clinical problem that includes urethra, bladder, and kidney infection, and it is the second common medical condition after anemia in pregnancy. In addition, asymptomatic bacteriuria is the most common condition where lack of diagnosis and treatment can have dangerous consequences for the mother and fetus (1-3). Among urinary tract infections, asymptomatic bacteriuria is important due to the lack of clinical symptoms. In pregnant women, physiological and anatomical changes in the urinary system and changes in the immune system during pregnancy increase the risk of an asymptomatic bacteriuria and in some cases, it leads to an infection of the urinary tract, which has a serious risk for the mother and the fetus (18).
Overall asymptomatic bacteriuria is a common infection. Pregnant women with asymptomatic bacteriuria are at an increased risk for harmful, maternal, and fetal complications that can be prevented by antibiotic therapy. In this study, the isolated organism was dominant E.coli. The present study showed that asymptomatic bacteriuria is a risk factor for preterm labor. It is suggested that urine culture should be performed as a routine assessment in all pregnant women during pregnancy and prevent from complications with antibiotic therapy (Dipstick leukocyte esterase and nitrite, as an evaluation method, is with positive and negative false positives).
