It is well documented that the prevalence of infertility is highest in low-income countries, with sub-Saharan Africa representing a significant example [19]. In numerous regions of Africa, it is estimated that up to 40% of women have reached the end of their reproductive years without having a child [34]. In their study, Polis et al. [35] estimated the prevalence of infertility in low-to-middle-income countries by applying a current duration approach to Demographic and Health Survey data. The findings indicated that the prevalence of infertility was 31.1%. An infertility belt has been described in Africa, extending from Angola to Tanzania and including Cameroon, Gabon, the Democratic Republic of Congo and Nigeria. The infertility belt exhibits a high prevalence of infertility, with rates exceeding 30% in certain regions [20].
In our study, we found a high prevalence of patients consulting for infertility, at 48.61%, which is consistent with the expected prevalence in the infertility belt of Africa. Sule et al. reported an even higher prevalence of 51.8% in Nigeria [14]. A lower prevalence of 11% was observed in the southern region of the DRC in Kasai [21]. In the DRC, the majority of couples experiencing infertility tend to consult general practitioners and traditional practitioners before consulting a gynaecologist. In the majority of cases, a gynaecologist is only consulted when previous treatments have been unsuccessful. It can be postulated that the availability of free gynaecological consultations during the outreach may have been a significant factor in motivating several infertile women to seek medical advice, which could explain the high prevalence of infertility observed in our study.
Among women experiencing infertility, 78.78% had secondary infertility, while 21.22% had primary infertility. The results of this study are in agreement with those of Bosenge et al. [24] in Kisangani, who reported that 67% of infertile couples had secondary infertility and 33% primary infertility. These findings are consistent with those from other Sub-Saharan African countries [16, 21, 26, 33]. The proportions of patients with primary and secondary infertility vary according to the aetiological particularities of each geographical region. The high prevalence of pelvic inflammatory disease (PID) among women with secondary infertility in our study and in other sub-Saharan environments is mainly due to the high incidence of sexually transmitted infections (STIs), unsafe abortions and complications of childbirth, among other factors. PID can lead to infertility in several ways, including the production of antisperm antibodies, tubal obstruction and other complications [25, 33].
The mean age of infertile women was found to be 33.91 ± 6.69 years, while the mean age of infertile men was 41.33 ± 6.05 years. In Kisangani, Bosenge-Nguma et al. [24] found a mean age of 32.85 ± 6.02 years for women, while Mubikayi et al. [21] in the southern region of the country reported a mean age of 33.85 ± 5.82 years. In the western of the DRC, Mboloko et al. [36] found a mean age of 33.85 ± 5.82 years region of Kinshasa, while in the southern region of the country, Mubikayi et al. [21] found a mean age of 33.7 ± 5.2 years. Sule et al. [14] found a mean age slightly higher (35 years) in Nigeria. In our communities, the majority of girls generally get married before the age of 26, which is the age of high fertility. Given the high fertility rate in our communities, they conceive earlier. Nevertheless, the observed decline in fertility at the age of 30, coupled with the high prevalence of infections affecting fertility in our communities [15, 25], provides a rationale for the average age of infertile women in our study. Among men, a significant association was observed between age and infertility, with men aged ≥35 years exhibiting a significantly higher prevalence of infertility (p-value=0.0000). The mean age of these men was 41.33±6.05 years. A review of the literature revealed that the probability of conception is 30% lower for men over the age of 40 than for men under the age of 30. This is attributed to the negative effects of advanced paternal age on sperm parameters, reproductive success, and offspring health [37].
Among women, the housewives constituted the largest proportion of cases of infertility, with 44.76% of cases. However, there was a significant association between seeking consultation for the purpose of conception and civil servants (p-value=0.0027), health professionals (p-value=0.0482), and housewives. In a study conducted in Sudan by Abdollah et al. [30], the housewives group was found to be the largest, yet no significant differences were observed between the various groups. The high number of housewives can be attributed to the fact that African society is traditionally oriented towards marriage. Furthermore, our study identified a correlation between the status of being a housewife, a health professional, or a government employee and the occurrence of infertility. This is likely due to several modifiable factors of infertility, such as stress, diet, long working hours, and so forth, which are known to affect fertility [38].
The study found that women residing in peripheral communes of Kisangani city (suburbs) (p-value=0.0161), those with a moderate (p-value=0.0292) or moderate-high (p-value=0.0319) socio-economic status, and married women (p-value=0.0000) were significantly more likely to seek consultation for infertility. In the city of Kisangani, numerous new settlements have emerged in the suburbs, populated by the middle class. It is evident that in Africa, an increase in socio-economic status is frequently accompanied by a transformation in lifestyle and dietary habits, leading to a greater prevalence of sedentary behaviours and a greater consumption of industrially produced products containing endocrine disruptors, heavy metals and high levels of fat. These changes are contributing to the onset of infertility [38-40].
The study revealed a statistically significant correlation between seeking medical attention for maternity and various factors related to sexual behaviour. These included being in a polygamous relationship (p-value=0.0000), having first sexual intercourse before the age of 18 (p-value=0.0000), admitting to having unprotected sex with a non-regular partner in the previous 6 months (p-value=0.0047), and having a history of treatment for genital infections in the previous 6 months (p-value=0.0106). A number of factors have been identified by various authors as being indicative of high-risk sexual behaviour (HRSB). These include the age at which the individual first engages in sexual activity, the use of unprotected intercourse, the number of sexual partners, the use of illicit substances, and the associated risks of infection, pregnancy, or even familial conflicts or legal issues. Those with HRSB are at an elevated risk of acquiring sexually transmitted infections (STIs) and other infections, which can result in a number of complications, including infertility [41, 42]. This justifies the results obtained in this study.
The results of our study indicate that a history of abdominal-pelvic surgery is associated with infertility (p-value = 0.0000). A similar result was found in Nigeria by Famurewa et al. They also found that there was an association between abdominal-pelvic surgery and tubal pathologies, probably due to adhesions, which explains the infertility and its duration [43].
With regard to the responsibility of the partners in the occurrence of the couple's infertility, our findings indicate that in 25.23% of cases, the woman was solely responsible for the couple's infertility, while in 18.16% of cases, the man was responsible. In 29.06% of cases, both partners were responsible. In 27.53% of cases, the cause of infertility remained unexplained. A study conducted in Kisangani by Bosenge-Nguma et al. [24] revealed that 31.62% of couples were infertile due to male factors alone, 39.71% due to female factors, and 13.23% due to a combination of male and female factors. In 15.44% of cases, the cause of infertility remained unexplained.
Among women patients, the study identified ovarian factors in 43.21%, uterine factors in 19.69% and tubal factors in 64.63%. The results indicated that ovarian factors were significantly associated with primary infertility. However, the uterine and tubal factors were not found to be associated with any type of infertility. In a similar study, Bosenge-Nguma et al. [24] found ovarian factors among 35.2% of patients, uterine factors among 31.5% of patients and tubal factors among 46.3% of patients. In previous studies, Nguma et al. [25] in Kisangani and Kalume et al. [26] in Goma found that 67.6% and 73.31% of infertile women had globally a tubal issue, respectively.
The analysis of the various causes of female infertility revealed that micropolycystic ovarian dystrophy was significantly associated with primary infertility (p-value=0.0033), while bilateral hydrosalpynx (p-value=0.0385) and bilateral tubal obstruction (p-value=0.0115) were associated with secondary infertility. Kalume et al. [26] also identified a correlation between tubal obstruction and secondary infertility in eastern Congo. In their study, Yu O et al. [44] observed an increase in the incidence of PCOS in individuals aged 16 to 20 and a decrease in those aged 26 to 30. These findings provide compelling evidence that PCOS begins at an earlier age and can explain its association with primary infertility, as observed in our study.
A survey of the prevalence of infections among infertile women revealed that 53.54% of the patients exhibited bacterial vaginosis. In their meta-analysis, Noortje et al. [45] estimated the prevalence of bacterial vaginosis (BV) in infertile women to be 19%, with a wide range from 10% in Ireland to 36.6% in Egypt. In the Democratic Republic of the Congo (DRC), Mulinganya et al. [46]found a prevalence of 26.3% during pregnancy in the eastern DRC. The high prevalence observed in this study may be attributed to the presence of HRSB in the study population.
The prevalence of HIV-positive serology was observed in 10.9% of cases, with no statistically significant difference observed between women with primary or secondary infertility. This prevalence is considerably higher than the 0.8% observed among women aged 15 and above in the DRC [47]. However, this prevalence is comparable to that observed among sex workers in Kinshasa, where a prevalence of 7.2% was found [48]. In Rwanda, Dhont et al. [49] observed a higher prevalence of 16% among infertile women. A total of 7.65% of patients exhibited positive serological results for syphilis, with no statistically significant difference observed between women with primary or secondary infertility. This prevalence is higher than that observed at the national level in the DRC (3.3%) among pregnant women, but lower than that observed by Katenga and Maindo in Kisangani (10.9%) [50]. In Rwanda, Dhont et al. [49] observed a prevalence of 6.7%, which is approximately the same as that observed in our study among infertile women and with no statistically significant difference between different types of infertility. As observed in our own study, Dhont et al. [49] noted a prevalent HRSB, although this was significantly more common among secondary infertile women. This may be indicative of the high prevalence of HIV and syphilis in our study.
The prevalence of chlamydia-positive serology was observed in 24.67% of cases, with a significant association noted between this and secondary infertility (p-value=0.0419). In Bukavu, eastern DRC, Mongane et al. [51] observed a prevalence of 23.4% and an association with tubal factor of infertility, which was predominantly observed in cases of secondary infertility.
With regard to TORCH infections, it was observed that toxoplasmosis (TOX) was present in 16.63% of cases, rubella (RV) in 44.36%, cytomegalovirus (CMV) in 15.87%, herpes simplex I (HSV I) in 17.21% and herpes simplex II (HSV II) in 15.68%. No significant association was observed between these infections and any type of infertility. In a study conducted in China by Han et al. [52], the prevalence of TOX, CMV and RV was found to be 3.20% (95% CI: 3.18-3.22%), 77.67% (95% CI: 77.62-77.71%) and 76.03% (95% CI: 75.98-76.07%), respectively. Abdo et al. [53] in the United Arab Emirates reported a prevalence of 12.4% for HSV-2. A multitude of factors, including nutritional status, vaccination status, socio-cultural habits, geographical and climatic variations, route of transmission, age, and others, influence the prevalence of TORCH infections. This is why the prevalence of these infections varies across the globe [52]. Furthermore, in our study, we only considered active infections by looking for IgM antibodies, which may explain the low prevalence of certain TORCH infections in our study.
The study demonstrated that 43.40% of patients exhibited positive anti-sperm antibody results, with no discernible correlation observed between this finding and any specific type of infertility. This prevalence is slightly higher than that reported by Maindo et al. five years ago in Kisnangi. In the global context, studies have demonstrated that ASA serology is positive in 1% to 36% of infertile couples. In Egypt, Emad M. Siam et al. [54] found a prevalence rate of 20%, while Adejuno et al. [55] in Nigeria reported a rate of 28.2%. The high prevalence of anti-sperm antibodies (ASA) observed in this study may be related to the high prevalence of infections found in our study. Indeed, previous research has demonstrated a correlation between infections and the production of anti-sperm antibodies [25, 33].
The findings of this study revealed that 44.55% of men exhibited spermogram abnormalities, which were significantly associated with primary infertility. The most prevalent abnormalities observed were oligospermia (21.03%), asthenospermia (12.24%) and leucopuospermia (13%). The only abnormality significantly associated with primary infertility was oligospermia (p-value=0.0113). In Kisangani, Bosenge-Nguma et al. (24) observed that 44.8% of men exhibited sperm abnormalities, with oligospermia and asthenospermia being the most prevalent abnormalities at 25.6% each. Juakali and Labama [27] observed that 57.6% of men exhibited sperm abnormalities, with oligospermia and asthenospermia being the most prevalent. The discrepancy between our findings and those of Juakali and Labama can be attributed to the fact that the aforementioned studies only considered male taxi-bike drivers. Given that the testicles are more exposed to heat, there is a greater risk of sperm abnormalities.