Results

General Description

During the study period, 5,172 admissions of pregnant women to the PCP were identified. Among those, we excluded 1,589 (30.7%) duplicate records and 205 (4.0%) records with insufficient information. In total, we analyzed 3,378 records. The median age was 24 (IQR 20–29) years, 98.5% were Afro-Colombian, 95.6% were from urban areas, 94.9% were at a basic or lower educational level, 93.8% were at the lowest socioeconomic level, 100% had subsidized health insurance, 78.7% were heads of households, and 19.1% had single marital status.

The median gestational age at initiation of the PCP was 12.3 (IQR 8.6–18.7) weeks, but 53.3% accessed the PCP in the first trimester of pregnancy. In total, 63.3% (2,139) women had >1 syphilis screening test; 270 had a positive rapid point-of-care treponemal test. Of those 270 patients, 86.7% (234) were considered cases with reactive nontreponemal tests, 11.1% (30) did not undergo the nontreponemal test, and 2.2% (6) had a nonreactive nontreponemal test. Finally, 96 mothers with newborns with congenital syphilis were reported.

The percentage of pregnant women screened for syphilis improved over time, increasing from <10% in 2018 to nearly 90% in 2022 (Figure 1). The number of participants entering the PCP each year varied; the lowest number was in 2020 and the highest was in 2022. The percentage of newborns with congenital syphilis per year decreased from 3.1% in 2018 to 1.8% in 2022 but increased during the interim years, 2019 and 2020 (Figure 1).

Factors Associated with Having Newborns with Congenital Syphilis

Of all pregnant women enrolled in the PCP, 53.1% who had newborns with congenital syphilis were not screened in the PCP. In the bivariate analysis, not having been screened through the PCP was associated with the probability of having newborns with congenital syphilis (adjusted odds ratio [aOR] 1.99, 95% CI 1.32–3.00; p = 0.001) (Table 1).

Factors Associated with the Lack of Syphilis Screening

In the bivariate analysis, age of <18 years or >35 years, basic or lower education, low socioeconomic status, single marital status, and accessing the PCP in the second or third trimester of gestation were associated with a lack of syphilis screening (Table 2). On the other hand, Afro-Colombian ethnicity and obstetric history were identified as protective factors.

Multivariate analysis revealed that independent factors associated with the lack of screening during the PCP were basic or lower educational level (aOR 2.22), lowest socioeconomic status (aOR 3.06), occupation as head of household (aOR 1.21), single marital status (aOR 2.02), and accessing the PCP in the second or third trimester of pregnancy (aOR 1.23) (Figure 2). Conversely, having had >3 previous pregnancies (aOR 0.69) and being of Afro-Colombian ethnicity (aOR 0.12) were identified as protective factors.

Factors of Mothers with Syphilis Associated with Having Newborns with Congenital Syphilis

In 234 pregnant patients, syphilis was detected during prenatal care; 41 had newborns with congenital syphilis. Of those 41 patients, 41.5% did not receive >1 dose of BPG >30 days before delivery, which was associated with a 4.31-fold increase in the probability of having newborns with the infection (Table 3).

Discussion

In this study conducted in pregnant women enrolled in a PCP on the Pacific coast of Colombia, we observed that the opportunity to prevent congenital syphilis was missed in 53.1% of pregnant women because of the lack of maternal screening. We found that the lack of screening through the PCP significantly increased the probability of having newborns with congenital syphilis, and the independent factors associated with not having had >1 screening test through the PCP included characteristics of higher maternal social vulnerability and the late access to the PCP. In addition, we observed that the opportunity to prevent congenital syphilis was missed in 41.5% of pregnant women with syphilis because of the lack of treatment with >1 dose of BPG >30 days before delivery, which increased the probability of having newborns with syphilis.

In the Americas, the prevalence of maternal syphilis and the incidence of congenital syphilis has increased substantially in recent years (22,23). In our study, we noted a progressive increase in the number of pregnant persons screened for syphilis during 2018–2022. However, the congenital syphilis case-patient ratio and trend could have been influenced by variability in access to the PCP during the years assessed, lack of screening, and potential surveillance biases. For example, screening in women with more risk factors might have increased in 2019, and underreporting also could have occurred, particularly in 2020. Nevertheless, the improvement in screening could indicate progress in syphilis surveillance and control in this area, possibly attributable to the implementation of the EMTCT Plus initiative (24) and Colombia’s Resolution 3280 of 2018 (25). This resolution established mandatory point-of-care screening using a rapid treponemal test for all pregnant women in each trimester of pregnancy and included administering BPG in case of a positive result (25). Although the merits of this screening approach have been debated, implementing point-of-care treponemal tests in low-income settings has been reported to increase the detection and treatment rates of syphilis (26). Therefore, that practice could be beneficial in the specific context of the studied region, although additional efforts are still needed to achieve the goal of 95% screening for syphilis in pregnant women. In addition, the defined criteria for congenital syphilis case-patients in Colombia are noteworthy and potentially advantageous (1,9). That definition could enable patients who might be overlooked using alternative criteria to be identified and treated (27). Nevertheless, future studies must be meticulous in evaluating the benefits and risks associated with these approaches, considering the diverse regional contexts (27).

Timely prenatal care is crucial for healthy pregnancy outcomes and early syphilis diagnosis (28), but certain sociodemographic factors might hinder healthcare professionals from getting to know patients, identifying their vulnerability factors, and providing comprehensive care (29,30). Independent factors that contributed to the lack of screening included basic or lower level of education, low socioeconomic status, serving as head of household, single marital status, and accessing prenatal care in the second or third trimester of pregnancy. Similar findings on socioeconomic level, prenatal care access, and compliance with screening were reported in the United States (20,31). In Colombia, late entry into prenatal care was associated with a low socioeconomic stratum (32), and a study in China found that single mothers (aOR 1.95) and women who had inadequate prenatal care (aOR 3.61) were at increased risk of having infants with congenital syphilis (30).

Several studies have reported that patients’ financial difficulties act as barriers to timely diagnosis of maternal syphilis (33,34). Those barriers can affect the ability of pregnant women to effectively access healthcare services despite being insured under the public healthcare system (35), especially when residing in rural areas within a fragmented healthcare system. Factors such as transportation could play a major role in late access or even lack of access (18,36), as evidenced in our study, where the population residing in rural areas was very low. Geographic barriers should be assessed in future studies on this region of Colombia.

Socioeconomic status, geographic barriers, low educational level, poor community or family social support, and the specific characteristics of the healthcare system in Colombia can result in limited contact with healthcare personnel and limited information (37), which leads to low awareness about the importance of timely prenatal care and detecting diseases such as syphilis early (11,18,27,33,35–38). Therefore, developing healthcare strategies and policies that ensure prompt and effective access to healthcare in the complex context of social determinants of health is imperative (38). Those strategies are especially crucial when most of the area’s residents exhibit vulnerable characteristics, and identifying population groups that are most socially vulnerable becomes essential to prioritize effective prevention and control strategies (31,38–40).

On the other hand, we identified factors that did not decrease the probability of receiving >1 maternal syphilis screening, such as a history of >3 pregnancies and Afro-Colombian ethnicity, which is likely related to improvements in healthcare personnel’s identification of high-risk pregnancies (41,42) and the predominance of Afro-Colombian ethnicity in the area. Those findings, combined with progressive improvements in the percentage of screened pregnant persons suggest that previously identified gaps in healthcare providers’ knowledge have gradually been addressed (11,42).

However, we observed that 41.5% of pregnant women with detected syphilis and with newborns with congenital syphilis did not receive >1 dose of BPG >30 days before delivery. That finding is particularly concerning because in the event of a positive result on the point-of-care treponemal test, administering a dose of BPG immediately is mandatory if the medical history has ruled out BPG allergy (9,25). A key factor to consider is delayed access to prenatal care, which can lead to late diagnosis and treatment and result in a missed opportunity to prevent congenital syphilis. In addition, although an allergy to penicillin might cause the physician to desensitize the patient to penicillin before initiating treatment (with possible loss of follow-up), true penicillin allergy is extremely rare (43), so this allergy is unlikely to result in a missed opportunity to prevent congenital syphilis. Hence, future studies are needed to identify the reasons behind those missed opportunities (20).

The missed opportunity to prevent congenital syphilis with BPG administration might be explained in part by documented deficiencies in healthcare professionals’ understanding of the appropriate approach to maternal syphilis (11,42). Of note, similar missed opportunities have been reported in other settings; a report from the United States found lack of adequate maternal treatment despite timely diagnosis was responsible for 30.7% of missed prevention opportunities (44), and in 2022, missed prevention opportunities because of inadequate treatment ranged from 15.7% to 54.5% in various regions of the United States (20). Those findings underscore the need for additional research and interventions to ensure the effective treatment of maternal syphilis, given the proven efficacy of BPG (8,27) and the heightened risk for congenital syphilis when BPG is omitted (30). Furthermore, the observation that 58.5% of mothers with diagnosed syphilis and newborns with congenital syphilis had received >1 dose of BPG raises concerns about the adequacy of treatment administered (9,20,45), and potential reinfections (46). Consequently, ensuring treatment of sex contacts and tailoring treatment with a penicillin-based regimen initiated >30 days before delivery, with dosing and spacing appropriate for the stage of maternal syphilis, are imperative (9,20,45).

Despite the small sample size and the predominance of participants with characteristics of social vulnerability, this study contributes valuable information to the literature on congenital syphilis. Furthermore, because of the variability in gestational age at entry into the PCP, the results might exhibit bias. However, consistent with other studies, late entry to the PCP was identified as a factor that affected the prevention and control of congenital syphilis (30,31,44). Therefore, we recommend interpreting our findings with caution; future research with larger sample sizes would achieve a more comprehensive understanding of the topic.

Overall, we observed a concerning 53.1% missed opportunity in congenital syphilis prevention because of the lack of maternal screening and a 41.5% missed opportunity because of the lack of maternal treatment. Maternal social vulnerability factors, such as basic or low educational level, low socioeconomic status, being head of the family, single marital status, and late access to prenatal care, increased the probability of not having maternal syphilis screening and having newborns with congenital syphilis. In addition, not having >1 dose of BPG >30 days before delivery, despite being a case-patient with syphilis detected at the PCP, increased the probability of having newborns with syphilis. Therefore, we recommend implementing a comprehensive multidisciplinary approach to identify and address those social vulnerability factors. Furthermore, we suggest intensifying efforts to ensure maternal syphilis is detected in a timely manner and treated adequately to mitigate elevated congenital syphilis incidence on the Pacific coast of Colombia.