This was a hospital-based matched case-control study of files of patients from January 1, 2019, to April 30, 2019. We studied patient’s files from January 1, 2014, to December 31, 2018.

We enrolled for study, participants who came for antenatal care at the outpatient unit and those admitted at the maternity of the Douala Referral Hospital.

The DRH is a tertiary care health facility that offers emergency obstetrics care, scientific treatment, teaching and research to a population of over three million inhabitants of the Littoral region and its environs. The hospital is located in Douala, an urban town, and also the economic capital of Cameroon. The Obstetrics and Gynecology department offers the following services: outpatient consultations, antenatal care (ANC), hospitalization, labor, delivery and gynecologic and obstetric surgery including laparoscopic and hysteroscopic surgery and colposcopy. The service is made up of eight obstetricians and gynecologists, one general medical practitioner and 39 midwives and nurses/assistant nurses. The outpatient department receives over 300 patients per week. There are thirty beds that assure in-service admission care of patients that are shared as eight common rooms and six private rooms and a nurse’s station. The labor room has four beds and there are two delivery rooms totaling two beds and a room for neonatal resuscitation. Averagely, there are 1250 births per year in the service.

The neonatology unit has a capacity of ten incubators, and there are six pediatricians and 15 specialized nurses that take charge of the neonatal intensive care unit. The service runs 24/7 and there is always one obstetrician/gynecologist and one pediatrician that take charge of call duties.

Files of pregnant women who came to the outpatient unit and those admitted to the maternity of the DRH were enrolled for the study.

Inclusion criteria

· Cases were files of consenting pregnant women who came for antenatal care and those admitted or gave birth at the maternity of the DRH and had a positive diagnosis of urinary tract infection by urine culture during the period of study.

· Controls were also files of consenting pregnant women without symptomatic/or asymptomatic UTI with negative urine culture at the OPD and those admitted or gave birth at the maternity of the DRH during the study period.

Exclusion criteria

· We excluded from the study all the files of pregnant women who did not give birth at the DRH and those who were receiving antibiotics for an infectious condition.

Matching criterion

A file of a woman in the case group was matched by age to one file (woman) in the control group giving a 1:1 ratio and participants were enrolled using the consecutive and convenience sampling method.

Ethical clearance for this study was obtained from the Institutional Review Board of the University of Bamenda and Administrative Authorization was obtained from the Delegation of Public Health for the Littoral Region and the Managing Director of the DRH (Ref. No. 044 AP/MINSANTE/HGD/DM/03/19). Furthermore, we carried-out pre-testing of the questionnaire on 15 pregnant women from the Bambui Health unit and adjustments were made on the questionnaire. Data was collected from patient’s files after obtaining verbal consent through phone calls to complete the questionnaires in case of missing information.

The data collection form contained information regarding:

· Socio-demographic characteristics: Profession, age, marital status, and residence.

· Laboratory tests: Urine culture and uropathogens isolated.

· Maternal-fetal outcome: Pyelonephritis, recurrent urinary tract infection during pregnancy, threatened preterm birth, threatened preterm labor, premature rupture of membranes, gestational age at delivery, birth weight, Apgar scores, sex, neonatal infection, neonatal jaundice, neonatal intensive care unit admission.

Data collected were double-checked, coded and entered into CSPro version 7.2 and exported and analyzed with SPSS version 23. The baseline characteristics of the study population were summarized using frequencies, mean and standard deviation. A comparison was made using binary logistic regression to determine the independent effect of the variables by calculating the strength of the association between UTI and adverse maternal-fetal outcomes of UTI using odds ratio (OR) and 95% confidence interval (CI). Adjusted OR (for variables which were statistically significant in binary logistic analysis) was computed using multivariable logistic regression to control the confounding variables. Statistical significance two-tailed was set at p < 0.05.

Cases were those with laboratory confirmation of UTI while those with negative laboratory tests served as controls. We respected the ethical principles of the Helsinki declaration while carrying out this study [11] and reported according to Strobe checklist for case-control studies.

The most commonly isolated bacterial pathogens in this study were Gram-negative bacteria: Escherichia coli (51.5%), Proteus mirabilis (15.5%), and Klebsiella spp (7.8%). This is consistent with others authors; Mohamed et al., Elzayat et al., Masinde et al., Amira et al. who reported a predominance of gram-negative microorganism and precisely Escherichia coli at a frequency of 47.4%, 70%, 47.2%, and 67.2% respectively [3] [12] [13] [14]. Furthermore, a study in Ethiopia reported that the most common isolates detected were E. coli (45.7%) followed by coagulase-negative Staphylococcus (17.1%) and S. aureus (8.6%) [15]. Also, Kim et al. reported that the predominant uropathogen isolated in their study was E. coli in 756/862 (87.7%) [16]. Besides UTI is common in pregnancy mostly because of stasis from the gravid uterus and elevated levels of progesterone secreted by the placenta that causes smooth muscle relaxation resulting in decreased peristalsis of the ureters, increased bladder capacity and urinary stasis. Furthermore, differences in urine pH and osmolality and pregnancy-induced glycosuria and aminoaciduria may facilitate bacterial growth [17] [18]. Besides, it may also result from poor hygiene methods of cleaning the anus after defecation and urogenital organs after micturition [19] [20]. The relatively short female urethra is frequently colonized with organisms from the gastrointestinal tract [21] [22]. Besides, most of these uropathogens like Escherichia coli are present in the gastrointestinal tract.

In this study, we found that women exposed to UTI in pregnancy were independently associated with pyelonephritis during the puerperal period, amnionitis, premature labor, and preterm delivery. These findings are consistent with those reported by Matuszkiewiez et al. [4]. It has been postulated that specific virulence determinants in uropathogenic strains of E. coli are associated with invasive infection and pyelonephritis in pregnancy. These include toxins and adhesions. The short attachment pili or fimbriae are organelles of adhesion allowing bacteria to colonize (multiplication and tissue invasion) the uroepithelial cells and prevent bacteria from urinary lavage or resist flushing. The frequencies of virulence-associated determinants are significantly high in case of pyelonephritis [23]. The pyelonephritis presented by women after delivery may also be due to inappropriate treatment of ASB or cystitis during pregnancy or to an undiagnosed ASB which led to renal tissue damage caused by bacterial endotoxins and systemic inflammatory response with endothelial injury [24]. Other studies have reported that women with urinary tract infection are independentlly associated with adverse pregnancy outcomes (preterm premature rupture of fetal membranes that ended up in preterm labor, and preterm birth of low birth weight neonates and amnionitis [25]. Furthermore, amnionitis may result from the premature rupture of membranes thereby favouring ascending infection (uropathogens) from the vagina into the uterus and therefore causing amniotic fluid contamination and infection. Later on, the heavily colonized birth canal may favour the transmission of microorganisms to the baby causing neonatal infection and neonatal intensive care unit admission [25]. This is consistent with our findings. The significant association between preterm labor and UTI has been well documented and the pathogenesis includes several theories as; uterine contractions may be induced by cytokines and prostaglandins, which are released by the microorganisms. Urinary tract infection affects premature labor directly through the development of amnionitis. Furthermore, bacterial enzymes such as collagenase may weaken the fetal membrane. It was also postulated that bacterial products such as phospholipase A and C or endotoxins might stimulate prostaglandin biosynthesis by the fetal membranes, which initiate labor [26] [27].

Our study furthermore strengthens the association between urinary tract infections and adverse maternal-fetal outcomes. Health education about personal hygiene, urine cultures early in pregnancy and during the third trimesters especially among pregnant women in low-resource settings like Cameroon should be considered in routine obstetric practice.

This is one of the few studies regarding UTI during pregnancy in our environment. However, the limitations of being a retrospective study may lead to recall bias, and selection of cases and controls by convenience sampling may make the results not be representative of the general population in Cameroon.