Abstract
Background.
Despite increasing syphilis incidence worldwide, little is known about the combined impact of maternal HIV and syphilis coinfection. We determined effects of HIV/syphilis coinfection in pregnancy on birth outcomes.
Methods.
We conducted two prospective birth cohort studies of pregnant women delivering in Uganda from 2017–2023. Our primary outcome was birthweight. Our secondary outcome was a composite adverse birth outcome, including low birthweight (<2.5kg), stillbirth, early neonatal death, or 5-minute APGAR<7. We compared outcomes by HIV and Treponema pallidum particle agglutination assay (TPPA) seropositivity and fitted multivariable logistic regression models to determine associations with outcomes.
Results.
Overall, TPPA seroprevalence was 12% (118/967) in this cohort comprised of 50% women with HIV (WHIV); 19% (94/483) among WHIV and 5% (24/484) among women without HIV. Only 48% of TPPA seropositive women reported syphilis testing during antenatal care. Combined stillbirth and early neonatal death were higher among TPPA seropositive participants: 12% (15/118) vs 4% (32/849) among seronegatives. Low birthweight was associated with HIV seropositivity (−0.1kg, 95%CI −0.15,−0.04), younger maternal age (0.01kg per year increase, 95% CI 0.01,0.02), and lower gestational age (0.07kg per week increase, 95% CI 0.06,0.09), but not TPPA serostatus. The composite adverse birth outcome was associated with lower maternal and gestational age at birth.
Conclusion.
We report high TPPA seroprevalence, low syphilis testing rates in antenatal care, and significant associations with adverse birth outcomes among WHIV in Uganda, emphasizing the need to improve prenatal syphilis testing and treatment.
Keywords: HIV/syphilis coinfection, adverse birth outcomes, maternal HIV, stillbirth, early neonatal death, Uganda, TPPA, pregnancy outcomes, sub-Saharan Africa, maternal coinfections
Clinical summary:
Syphilis coinfection was common in pregnant women with HIV in Uganda and linked to adverse birth outcomes, but antenatal testing rates were low – highlighting an urgent need to strengthen antenatal syphilis screening and treatment to improve maternal and neonatal health.
BACKGROUND
Syphilis continues to surge worldwide, including in sub-Saharan Africa, where the prevalence of syphilis infection among pregnant women is estimated at 2.7%, complicating approximately one million pregnancies each year [1]. The adverse impacts of syphilis infection are further exacerbated by the global shortages of penicillin [2], the preferred treatment for pregnant women. Children born to women with untreated syphilis infection are at higher risk of adverse perinatal outcomes, including a 40% risk of stillbirth or early neonatal death [3, 4]. A recent meta-analysis demonstrated that adverse birth outcomes, including stillbirth, neonatal death, prematurity, and low birthweight, were 52% more common among women with syphilis than those without syphilis [5]. The World Health Organization (WHO) lists syphilis as the second leading cause of stillbirths globally and recommends syphilis screening in antenatal care (ANC) to enhance diagnosis and treatment and reduce the risk of adverse outcomes [6]. However, in sub-Saharan Africa, shortages of syphilis test kits, delayed first antenatal visits, and understaffed health facilities have hindered efforts to screen pregnant women in accordance with WHO guidelines. This has resulted in lack of reliable data on syphilis prevalence in pregnancy, and inadequate estimates of its impact on birth outcomes [7].
HIV infection in pregnancy is also prevalent in sub-Saharan Africa, with seroprevalence in Uganda estimated at 5.5% [8]. Like syphilis, HIV is associated with an increased risk of adverse birth outcomes, including low birthweight, preterm birth, stillbirth, and neonatal death [9]. HIV and syphilis are commonly acquired and transmitted together, and coinfection is highly prevalent [10–12], especially in sub-Saharan Africa [10, 13]. Furthermore, studies from high-income countries show that syphilis coinfection increases the risk of HIV treatment failure [14], in utero HIV transmission [10], low birthweight, preterm birth, stillbirth [15], and intrauterine fetal death [16]. A cohort study from neighboring Tanzania published in 2002 documented that 25% of untreated TPPA- and RPR-positive mothers delivered a stillbirth, and 33% delivered a low-birthweight neonate, both prevented by a single intramuscular dose of benzathine penicillin [17, 18]. However, there is a lack of contemporary data describing the effects of maternal HIV and syphilis coinfection on birth and neonatal outcomes in sub-Saharan Africa [15], where approximately 65% of people living with HIV reside.
Therefore, there is an urgent need to define the separate and combined impact of HIV and syphilis coinfection in the most affected global settings to advocate for and implement appropriate and effective public health measures to improve maternal and child health outcomes [19]. To address this knowledge gap, we conducted two prospective birth cohort studies in Uganda to determine associations between maternal HIV and syphilis coinfection and birth outcomes in Uganda.
METHODS
Study Site, Participant Recruitment, and Ethics
We conducted post-hoc analysis of data from two prospective birth cohort studies of women delivering at Mbarara Regional Referral Hospital (MRRH) in southwestern Uganda from 2017–2023. MRRH serves a semi-rural population of approximately nine million and has >9,000 deliveries annually [20].
The first cohort (2017–2018) was powered to determine the association between maternal HIV infection and chronic placental inflammation [21], while the second cohort (2019–2023) was powered to determine associations between placental abnormalities and child health outcomes. For both cohorts, we consecutively enrolled women with HIV (WHIV) and the next eligible HIV-uninfected woman presenting for delivery after each WHIV. In the second cohort, we enrolled a subgroup of women in the second pregnancy trimester to study changes in placental vascular and growth factors over time, whom we followed by phone throughout pregnancy and reminded to attend ANC visits.
For both cohorts, eligibility for enrollment included age ≥18 years and early-stage labor. Exclusion criteria included multiple gestation pregnancy, inability to collect the placenta or be contacted by telephone after discharge, and inability to speak English or Runyankole (the local language). WHIV were only eligible if they reported taking combination antiretroviral therapy (ART) within the last 30 days.
Both studies strictly adhered to the ethical standards in the 1964 Declaration of Helsinki and its later amendments and were approved by the Institutional Ethics Review Boards at Mbarara University of Science and Technology (MUST, 11/03–17, 10/06–19), Partners Healthcare (2017P001319; 2019P003248), and the Uganda National Council of Science and Technology (HS/2255; HS/2697). All participants provided written informed consent.
Data Collection
After delivery and before discharge, we administered a standardized questionnaire to each participant and abstracted maternal and neonatal medical charts to collect maternal sociodemographics, medical and obstetric history, pregnancy, ANC, and maternal and neonatal in-hospital outcomes. We obtained details of HIV-specific care from each WHIV’s care clinic. We calculated gestational age using the participants’ report of their last normal menstrual period or chart documentation. We entered data into a Research Electronic Data Capture (REDCap) database [22].
Blood Collection and HIV Syphilis Testing
For the first cohort, we collected maternal blood at enrollment for HIV antibody point-of-care testing only for women who did not report being HIV seropositive. In the second cohort, we tested maternal blood from all participants for HIV regardless of their reported HIV serostatus. In both cohorts, we used Alere Determine HIV-1/2 point-of-care antibody assay to test for HIV (Abbott, Chicago, USA), and for those testing HIV-positive, we performed HIV viral load (Xpert, Cepheid, Sunnyvale, USA) and CD4+ T-cell count determination if not already performed within the last six months or results were not available. For both cohorts, we tested maternal blood for syphilis using a Treponema pallidum particle agglutination (TPPA) rapid test (SD Bioline Syphilis 3.0; Standard Diagnostics, Suwon City, Korea). We tested TPPA-positive maternal plasma samples in the second cohort using rapid plasma reagin (RPR Carbon Test, Cypress Diagnostics, Hulshout, Belgium).
Data Analysis
For this analysis, we included all participants enrolled in both cohorts. We compared demographics, obstetric characteristics, and outcomes by maternal HIV serostatus and TPPA status using chi-squared tests for categorical variables; and Wilcoxon rank-sum, Kruskal-Wallis, t-tests, and ANOVA for continuous variables. Results were considered statistically significant for P-values <0.05.
Our primary exposure of interest was maternal HIV and syphilis coinfection status, categorized into four groups: dual-positive, TPPA-seropositive only, HIV-seropositive only, and dual-negative. Our primary outcome was birthweight in kilograms. Our secondary outcome was a dichotomous composite adverse birth outcome of commonly-used measures (as in our prior work [20]), including one or more of the following: stillbirth (where the baby was born dead at a gestational age ≥28 weeks), low birthweight (<2.5 kg), early neonatal death <14 days of birth, and/or 5-minute APGAR score <7. To determine independent associations between HIV and syphilis coinfection status and the primary birthweight and secondary composite adverse birth outcomes, we created separate multivariable linear and logistic regression models, respectively. We included an HIV×TPPA product term in both models to explore whether HIV modified the effect of TPPA positivity on each outcome.
In both models, we adjusted for potential confounders of the relationship between HIV and syphilis infection outcomes. ANC attendance was dichotomized as ≥4 or <4 visits, based on the Uganda recommendations when the first cohort was enrolled [23]). We also created separate models restricted to WHIV that included CD4+ T-cell count, HIV viral load, and pre- vs post-conception ART start. All variables with P-value <0.05 in the final models were considered significant predictors. We performed analyses using STATA (Version 16.0, StataCorp, College Station, TX).
RESULTS
Participant Characteristics
There were 352 participants in the first cohort, of whom 176 were WHIV taking ART. There were 618 participants in the second cohort, of whom 308 WHIV. The combined analytic cohort size was 970 pregnant women, with 3/970 (0.3%) missing syphilis testing results. Of the 967 women with syphilis results, 94/967 (10%) were dual-positive, 24/967 (2%) were TPPA-seropositive only, 389/967 (40%) were HIV-seropositive only, and 460/967 (48%) were dual-negative (Table 1). Among WHIV, 19% were TPPA positive (94/483) versus 5% (24/484) among women without HIV. The mean age of TPPA-seropositive only women was significantly lower (25, standard deviation [SD] 5 years) than dual-positive (28, SD 6 years), HIV-seropositive only (28, SD 6 years), and dual-negative (27, SD 6 years) women (P<0.001, Table 1).
Table 1.
Demographics and clinical history of the combined cohort (N = 970). Data were missing for <1% for each variable.
| Maternal TPPA testa | Positive n = 118 (12%) | Negative n = 849 (88%) | P-value | ||
|---|---|---|---|---|---|
|
| |||||
| Maternal HIV test | Positive n = 94 (10%) Dual-positive |
Negative n = 24 (2%) TPPA seropositive only |
Positive n = 389 (40%) HIV seropositive only |
Negative n = 460 (48%) Dual-negative |
|
|
| |||||
| DEMOGRAPHICS | |||||
|
| |||||
| Maternal age in years, mean (SD) | 28 (6) | 25 (5) | 28 (6) | 27 (6) | <0.001 |
|
| |||||
| Married | 81 (87) | 22 (92) | 346 (89) | 428 (93) | 0.12 |
|
| |||||
| Formally employed | 39 (42) | 4 (17) | 157 (40) | 198 (43) | 0.08 |
|
| |||||
| Monthly income in USD, median (IQR) | 27 (14, 54) | 22 (19, 27) | 30 (16, 81) | 41 (22, 81) | <0.001 |
|
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| OBSTETRICS | |||||
|
| |||||
| Parity | <0.001 | ||||
| Primiparous (1st delivery) | 13 (14) | 9 (38) | 76 (20) | 145 (32) | |
| Multiparous (2nd – 4th delivery) | 65 (69) | 12 (50) | 233 (60) | 205 (45) | |
| Grand multiparous (≥ 5th delivery) | 16 (17) | 3 (13) | 80 (21) | 110 (24) | |
|
| |||||
| ≥4 ANC visits during this pregnancy | 69 (73) | 17 (71) | 286 (74) | 340 (74) | 1.0 |
|
| |||||
| Gestational age in weeks, mean (SD) | 39 (3) | 39 (2) | 39 (2) | 39 (2) | 0.15 |
|
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| SELF-REPORTED TESTING, DIAGNOSES, AND TREATMENTS | |||||
|
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| Self-reported diagnoses during this pregnancy | |||||
| Hypertensive disorders | 3 (3) | 0 (0) | 10 (3) | 12 (3) | 0.85 |
| Diabetes diagnosis | 0 (0) | 0 (0) | 0 (0) | 1 (0.2) | 0.78 |
| Urinary tract infection | 13 (14) | 2 (8) | 38 (10) | 41 (9) | 0.51 |
| Malaria diagnosis | 7 (8) | 0 (0) | 23 (6) | 29 (6) | 0.58 |
| Self-reported syphilis testing in ANCb | 44 (47) | 13 (54) | 151 (39) | 180 (39) | 0.41 |
| Self-report of ≥1 possible STI symptoms in last | 35 (37) | 13 (54) | 143 (37) | 169 (37) | 0.39 |
| 1 week prior to deliveryc | |||||
| Self-reported syphilis diagnosis | <0.001 | ||||
| During this pregnancy | 23 (24) | 10 (42) | 21 (5) | 11 (2) | |
| During a prior pregnancy | 3 (3) | 1 (4) | 4 (1) | 8 (2) | |
| While not pregnant | 4 (4) | 1 (4) | 4 (1) | 4 (1) | |
| Never | 63 (68) | 12 (50) | 360 (93) | 436 (95) | |
| Self-reported syphilis treatmentd | 0.54 | ||||
| Herbs | 0 (0) | 1 (8) | 1 (3) | 1 (4) | |
| Medicine | 28 (93) | 9 (75) | 27 (93) | 21 (91) | |
| Other | 1 (3) | 0 (0) | 0 (0) | 0 (0) | |
| None | 1 (3) | 2 (17) | 1 (3) | 1 (4) | |
3 participants were missing syphilis testing results
Only collected for participants in the second cohort
STI = sexually transmitted infection; symptoms reported included abnormal or foul-smelling vaginal discharge, vaginal or vulvar itching, pain or burning with urination, increased urinary frequency.
Only collected for participants who self-reported a positive syphilis diagnosis
The proportion of women attending ≥4 ANC visits during pregnancy did not differ by group (P=1.0, Table 1) and 4/970 (0.4%) participants reported no ANC attendance. Gestational age at delivery was similar between groups (39 weeks, P=0.15, Table 1). Significantly fewer WHIV were primiparous: 13/94 (14%) of dual-positive and 76/389 (20%) of the HIV-seropositive only versus 9/24 (38%) of TPPA-seropositive only and 145/460 (32%) of dual-negative groups (P<0.001, Table 1). Self-reported comorbidities during the current pregnancy were similar between groups (Table 1). While self-reported syphilis testing in antenatal care was only reported in the second cohort and did not differ by group (3–46%, P=0.41), self-reported syphilis diagnosis during this pregnancy was expectedly higher among the dual-positive (23/94, 24%) and TPPA-seropositive only (10/24, 42%) groups versus the HIV-seropositive only (21/389, 5%) and dual-negative groups (11/460, 2%); self-reported syphilis diagnosis during a prior pregnancy was also slightly higher among the dual-positive (3/94, 3%) and TPPA-seropositive only (1/24, 4%) groups versus the HIV-seropositive only (4/389, 1%) and dual-negative groups (8/460, 2%, P<0.001, Table 1), consistent with the test-positivity rates. Self-reported treatments for syphilis were similar between groups, with 75–93% reporting receiving medicine for treatment (P=0.54, Table 1).
Among WHIV, 63/94 (67%) dual-positive participants reported initiating ART pre-conception and 28/94 (30%) had a detectable HIV viral load (Table 2). Of all 118 TPPA-seropositive participants, 65/118 (55%) had RPR titers available, of whom 55/65 (85%) were dual-positive and 10/65 (15%) were HIV-seronegative (Table 3). For dual-positive women, 8/55 (15%) had non-reactive RPR, 39/55 (71%) were reactive with titers <1:32, and 8/55 (15%) were ≥1:32 (Table 3).
Table 2.
Characteristics of people living with HIV (n = 484).
| Maternal TPPA testa | Positive n = 94 (19%) | Negative n = 389 (81%) | P-value |
|---|---|---|---|
|
| |||
| Reported starting ART before conception | 64 (68) | 262 (67) | 0.58 |
|
| |||
| Most recent HIV viral load during pregnancy was detectableb,c | 28 (30) | 96 (26) | 0.44 |
|
| |||
| HIV viral load during pregnancy, median (IQR) | 0 (0, 555) | 0 (0, 40) | 0.29 |
|
| |||
| CD4 count during pregnancy, median (IQR) | 440 (306, 639) | 474 (310, 669) | 0.51 |
|
| |||
| Current ART regimen | 0.18 | ||
| DTG/TDF/3TC | 20 (22) | 63 (16) | |
| EFV/TDF/3TC or FTC | 68 (74) | 279 (73) | |
| Other | 4 (4) | 41 (11) | |
|
| |||
| Reported being prescribed Septrin/Bactrim | 77 (84) | 297 (77) | 0.24 |
1 participant was missing syphilis testing results
Detectable HIV viral load was defined as >400 for the first cohort and >50 for the second cohort
17 participants were missing HIV viral load results
Table 3.
Rapid plasma reagin (RPR) testing results among participants with positive TPPA screening tests.a
| Maternal HIV test | Positive n = 55 (85%) | Negative n = 10 (15%) | P-value |
|---|---|---|---|
|
| |||
| Maternal serum RPR result | 0.84 | ||
| Negative/non-reactive | 8 (15) | 1 (10) | |
| Very low titre (< 1:8) | 25 (45) | 4 (40) | |
| Low titre (1:8 to 1:32) | 14 (25) | 4 (40) | |
| High titre (≥ 1:32) | 8 (15) | 1 (10) | |
RPR testing was only performed for the second cohort.
Primary and secondary outcomes
Our primary outcome was birthweight, and our secondary outcome was a composite adverse birth outcome including ≥1 of: stillbirth, low birthweight <2.5 kg, early neonatal death <14 days after birth, and/or 5-minute APGAR score <7. Overall, 56/967 (6%) of the participants’ babies had low birthweight, including 9/94 (10%) dual-positive, 3/24 (13%) TPPA-seropositive only, 24/389 (6%) HIV-seropositive only, and 20/460 (4%) dual-negative individuals (P=0.10, Table 4). Collectively, 84/967 (9%) women met criteria for the composite adverse birth outcome, occurring in 13/94 (14%) dual-positive, 3/24 (13%) TPPA-seropositive only, 35/389 (9%) HIV-seropositive only, and 33/460 (7%) dual-negative participants (P=0.18, Table 4). This included a total of 18/967 (2%) stillbirths, with a significantly higher proportion among TPPA-seropositive participants: 5/94 (5%) of dual-positive and 1/24 (4%) of TPPA-seropositive only groups experienced stillbirths, versus 8/389 (2%) of HIV-seropositive only and 4/460 (1%) of the dual-negative groups (P=0.02, Table 4). Early neonatal death occurred among 29/967 (3%) individuals, including 8/94 (9%) dual-positive, 1/24 (4%) TPPA-seropositive only, 13/389 (3%) HIV-seropositive only, and 7/460 (2%) dual-positive individuals (P=0.10, Table 4). The 5-minute APGAR score was <7 in 17/935 (2%) of live-born participants with recorded scores, including 1/94 (1%) dual-positive, 0/24 (0%) TPPA-seropositive only, 4/389 (1%) HIV-seropositive only, and 12/460 (3%) dual-negative participants (P=0.29, Table 4). The lowest mean birthweight was 3.1kg in the dual positive group versus 3.3kg in the TPPA seropositive only, 3.1kg in the HIV-seropositive, and 3.2kg in the dual negative groups. Mean birthweight did not differ significantly among the four groups (P = 0.07, Table 4). Of live-born babies, 37/970 (4%) and 34/970 (4%) were missing 1-minute and 5-minute APGAR scores, respectively.
Table 4.
Intrapartum factors and birth outcomes of the combined cohort (N = 970).
| Maternal TPPA testa | Positive n = 118 (12%) | Negative n = 849 (88%) | P-value | ||
|---|---|---|---|---|---|
| Maternal HIV test | Positive n = 94 (80%) |
Negative n = 24 (20%) |
Positive n = 389 (46%) |
Negative n = 460 (54%) |
|
| Stillbirth | 5 (5) | 1 (4) | 9 (2) | 4 (1) | 0.02 |
| Low birthweight (<2.5 kg) | 9 (10) | 3 (13) | 24 (6) | 20 (4) | 0.10 |
| Birthweight (mean, standard deviation) | 3.1 (0.5) | 3.3 (0.6) | 3.1 (0.5) | 3.2 (0.5) | 0.07 |
| Early neonatal death | 8 (9) | 1 (4) | 13 (3) | 7 (2) | 0.02 |
| Live birth with 5-minute APGAR <7 | 1 (1) | 0 (0) | 4 (1) | 12 (3) | 0.29 |
| Composite adverse birth outcome | 13 (14) | 3 (13) | 35 (9) | 33 (7) | 0.18 |
| Cesarean delivery | 35 (37) | 10 (42) | 174 (45) | 134 (29) | <0.001 |
| Neonate admitted to paediatric ward or neonatal intensive care unit after delivery | 10 (12) | 4 (17) | 49 (13) | 63 (14) | 0.87 |
3 participants were missing syphilis testing results
Birth and early neonatal outcomes
Dual-negative women had a significantly lower proportion of deliveries by cesarean (133/460, 29%) than dual-positive (35/94, 37%), TPPA-seropositive only (10/24, 42%), and HIV-seropositive only (174/389, 45%) women (P<0.001, Table 4). The proportion of neonates admitted to the pediatric ward or neonatal intensive care unit after delivery did not differ significantly among the four groups (P=0.62, Table 4). Stillbirth (6 [5%] vs 13 (2%), P=0.009), early neonatal death (9 [8%] vs 21 (2%), P=0.01), and the composite adverse birth outcome (16 [14%] vs 69 (8%), P=0.049) were significantly more common among TPPA seropositive than seronegative participants overall, regardless of maternal HIV serostatus (Table 5).
Table 5.
Most severe birth outcomes of the combined cohort (N = 970).
| Maternal TPPA and RPR test resulta | TPPA negative n = 849 (88%) |
TPPA positive (all) n = 118 (12%) |
P-value | TPPA negative n = 849 (88%) |
TPPA positive, RPR positive n = 56 (6%) |
P-value |
|---|---|---|---|---|---|---|
| Stillbirth | 13 (2) | 6 (5) | 0.009 | 13 (2) | 3 (5) | 0.07 |
| Early neonatal death | 21 (2) | 9 (8) | 0.01 | 21 (2) | 5 (9) | 0.005 |
| Composite adverse birth outcome | 69 (8) | 16 (14) | 0.049 | 69 (8) | 9 (16) | 0.04 |
3 participants were missing syphilis testing results
Multivariable analyses of associations between HIV serostatus and TPPA positivity and outcomes
In our primary multivariable analysis, maternal HIV seropositivity was independently associated with lower birthweight (adjusted beta coefficient [aβ] −0.10, 95% confidence interval [CI] −0.15, −0.04, P=0.002) and greater maternal and gestational age at birth were associated with higher birthweight (aβ 0.01, 95% CI 0.01, 0.02, P<0.001 and aβ 0.07, 95% CI 0.06, 0.09, P<0.001, respectively, Table 6). In unadjusted models, attending ≥4 ANC visits was associated with higher birthweight, but not in adjusted analyses (P=0.08, Table 6). When restricted to WHIV alone, greater maternal age (aβ 0. 02, 95% CI 0.01, 0.02, P<0.001) and gestational age at birth (aβ 0.07, 95% CI 0.05, 0.09, P<0.001) were significantly associated with higher birthweight (Table 7). In unadjusted analysis, attending ≥4 ANC visits was significantly associated with lower birthweight, but not in multivariable analysis (P=0.24, Table 7).
Table 6.
Regression models for primary birthweight outcome and secondary composite adverse birth outcome among all participants.
| Unadjusted | Adjusted | |||
|---|---|---|---|---|
|
| ||||
| Primary birthweight outcome in kilograms | β (95% CI) | P-value | aβ (95% CI) | P-value |
|
| ||||
| Maternal HIV+ serostatus | −0.07 (−0.14, −0.01) | 0.02 | −0.10 (−0.15, −0.04) | 0.002 |
| Maternal TPPA+ serostatus | −0.04 (−0.14, 0.05) | 0.35 | 0.02 (−0.07, 0.11) | 0.72 |
| Maternal age in years | 0.01 (0.01, 0.02) | <0.001 | 0.01 (0.01, 0.02) | <0.001 |
| ≥4 ANC visits during this pregnancy | 0.11 (0.04, 0.18) | 0.001 | 0.06 (−0.01, 0.12) | 0.08 |
| Gestational age at birth in weeks | 0.08 (0.06, 0.09) | <0.001 | 0.07 (0.06, 0.09) | <0.001 |
|
| ||||
| Secondary composite adverse birth outcome | OR (95% CI) | P-value | aOR (95% CI) | P-value |
|
| ||||
| Maternal HIV+ serostatus | 1.36 (0.86, 2.14) | 0.18 | 1.24 (0.75, 2.06) | 0.40 |
| Maternal TPPA+ serostatus | 1.81 (1.01, 3.25) | 0.046 | 1.52 (0.79, 2.95) | 0.21 |
| Maternal age in years | 0.97 (0.94, 1.01) | 0.18 | 0.97 (0.93, 1.01) | 0.11 |
| ≥4 ANC visits during this pregnancy | 0.60 (0.37, 0.96) | 0.03 | 0.79 (0.47, 1.32) | 0.36 |
| Gestational age at birth in weeks | 0.66 (0.59, 0.74) | <0.001 | 0.66 (0.59, 0.75) | <0.001 |
Multivariable estimates are adjusted only for the covariates listed in this table; no additional variables were included in the models.
Table 7.
Regression models for primary birthweight outcome and secondary composite adverse birth outcome restricted to participants living with HIV.
| Unadjusted | Adjusted | |||
|---|---|---|---|---|
|
| ||||
| Primary birthweight outcome in kilograms | β (95% CI) | P-value | aβ (95% CI) | P-value |
|
| ||||
| Maternal TPPA+ serostatus | −0.05 (−0.16, 0.06) | 0.38 | −0.02 (−0.11, 0.10) | 0.96 |
| Maternal age in years | 0.02 (0.01, 0.02) | <0.001 | 0.02 (0.01, 0.02) | <0.001 |
| ≥4 ANC visits during this pregnancy | 0.11 (0.02, 0.21) | 0.02 | 0.06 (−0.04, 0.15) | 0.24 |
| Gestational age at delivery in weeks | 0.07 (0.06, 0.09) | <0.001 | 0.07 (0.05, 0.09) | <0.001 |
| Preconception ART initiation | 0.08 (0.01, 0.17) | 0.09 | 0.00 (−0.10, 0.10) | 0.98 |
| CD4 count during pregnancy | −5e-5 (−1e-4, 2e-4) | 0.58 | −7e-5 (−2e-4, 8e-5) | 0.32 |
| Detectable HIV viral load during this pregnancy | −0.03 (−0.13, 0.07) | 0.50 | 0.00 (−0.09, 0.10) | 0.92 |
|
| ||||
| Secondary composite adverse birth outcome | OR (95% CI) | P-value | aOR (95% CI) | P-value |
|
| ||||
| Maternal TPPA+ serostatus | 1.64 (0.83, 3.25) | 0.15 | 1.50 (0.71, 3.16) | 0.29 |
| Maternal age in years | 0.92 (0.86, 0.97) | 0.004 | 0.90 (0.84, 0.96) | 0.002 |
| ≥4 ANC visits during this pregnancy | 0.57 (0.30, 1.08) | 0.09 | 0.61 (0.31, 1.20) | 0.15 |
| Gestational age at delivery in weeks | 0.77 (0.68, 0.87) | <0.001 | 0.78 (0.68, 0.90) | 0.001 |
| Preconception ART initiation | 0.95 (0.50, 1.79) | 0.88 | 1.66 (0.78, 3.51) | 0.19 |
| CD4 count during this pregnancy in cells/mm3 | 1.00 (1.00 – 1.00) | 0.14 | 1.00 (1.00 – 1.00) | 0.30 |
| Detectable HIV viral load during this pregnancy | 1.04 (0.53, 2.04) | 0.91 | 0.88 (0.42, 1.87) | 0.75 |
Multivariable estimates are adjusted only for the covariates listed in this table; no additional variables were included in the models.
In our secondary multivariable analysis, greater gestational age at birth was independently associated with decreased odds of the secondary adverse birth outcome (adjusted odds ratio [aOR] 0.66, 95% CI 0.59, 0.75, P<0.001, Table 6). In unadjusted analysis, TPPA-seropositivity and attending ≥4 ANC visits were significantly associated with the secondary composite adverse birth outcome, but not in adjusted analysis (P=0.21 and P=0.36, respectively, Table 6). Maternal age was not significantly associated with the composite adverse birth outcome (P=0.11, Table 6). When restricted to WHIV, greater maternal age (aOR 0.90, 95% CI 0.84, 0.96, P=0.002) and gestational age at birth (aOR 0.78, 95% CI 0.68, 0.90, P=0.001) were associated with decreased odds of an adverse birth outcome (Table 7). Attending ≥4 ANC visits was not associated with the composite adverse birth outcome (P=0.15, Table 7).
The HIV×TPPA product term was not statistically significant in the primary or secondary outcome models (P=0.24 and P=0.68) and was excluded from the final models.
DISCUSSION
Our main objective was to describe birth outcomes among women living with coinfection of HIV and syphilis in pregnancy in Uganda. We observed a 12% prevalence of TPPA seropositivity in this population comprised of 50% WHIV. Of TPPA seropositive individuals, 80% were WHIV resulting in 19% TPPA positivity among WHIV. In multivariable regression analyses, HIV seropositivity was associated with lower birthweight, and in univariate analysis, TPPA seropositivity was associated with an increased risk of stillbirth, early neonatal death, and the composite adverse birth outcome.
Our report of 19% TPPA seropositivity among WHIV is higher than other recent studies reporting syphilis prevalence ranging from 5–10% among people living with HIV in Africa [13, 24, 25]. Although the 19% TPPA seropositivity we report could reflect a rising incidence of T. pallidum infection in Uganda, TPPA positivity indicates lifetime exposure to syphilis and may not reflect syphilis infection affecting the current pregnancy. In line with the syphilis screening algorithm in Uganda and to better assess active syphilis infection, we measured RPR for participants screening TPPA positive in our second cohort. Of these, 56/65 (86%) were positive, though most were low-titer positives at 1:1 to 1:16 that could indicate untreated latent infection, reinfection, or a serofast state. The nine RPR titers ≥1:32 could indicate up to 9% prevalence of active syphilis infection in our second cohort, similar to prevalence rates reported by other recent studies in sub-Saharan Africa. However, comparing syphilis prevalence across studies remains challenging due to different testing strategies, RPR thresholds, and variations in treponemal and nontreponemal test result reporting. RPR also has suboptimal test characteristics, with performance dependent on heat and humidity – results vary between experienced users, making interpretation of single RPR measurements difficult [26].
Despite the Uganda Ministry of Health’s recommendation for universal syphilis screening during ANC [27], less than half (48%) of TPPA seropositive women in our study reported being tested for syphilis during ANC. This finding aligns with previous reports of low rates of self-reported sexually transmitted infection testing in sub-Saharan Africa [28]. Although a significant proportion (64%) of TPPA seropositive women in our study self-reported never having a syphilis diagnosis, 88% of those who reported a diagnosis indicated receiving medical treatment. High treatment uptake in this population demonstrates the importance of regular screening during ANC.
In our primary analysis, we found that maternal HIV seropositivity was associated with lower birthweight but that the effect of HIV seropositivity on birthweight did not differ by TPPA serostatus. The average magnitude of the impact of HIV positivity on birthweight was small (100 grams), similar to a prior study in Uganda, where maternal HIV seropositivity was associated with an average of 120 grams lower birthweight [29]. Additional studies reported similar findings across sub-Saharan Africa [30]. Interestingly, a meta-analysis of cohort studies of WHIV and uninfected women found that the risk of low birthweight among WHIV is more pronounced in low-income countries [31], suggesting that socioeconomic factors including low income level, low education levels, single motherhood [32], poor nutritional status, and geographic barriers may contribute to the increased risk measured by the association between birthweight and HIV seropositivity. We also found that lower maternal and gestational age at birth were associated with lower birthweight, including when models were restricted to WHIV.
In our analysis, stillbirth, early neonatal death, and the composite adverse birth outcome were significantly more common among TPPA seropositive than TPPA seronegative women, consistent with prior literature [5]. However, in our multivariable models of the secondary composite adverse birth outcome, neither HIV nor TPPA seropositivity were significantly associated with the outcome, which we suspect is due to the overall low number of adverse outcomes (19 stillbirths and 29 neonatal deaths), limiting power to detect associations. Future studies should determine the effect of HIV-syphilis coinfection on stillbirth and neonatal death. Furthermore, because TPPA seropositivity reflects lifetime exposure to Treponema pallidum, including past and current infections, the strength of the association observed in our participants could be biased towards the null by including treated or resolved infections. However, a larger cohort study in Botswana also found no significant effect modification by HIV status in the association between syphilis and birth outcomes, even when defining syphilis infection based on reactive RPR testing and not treponemal-specific tests [15]. In our secondary model including all participants, only lower gestational age was associated with the composite adverse birth outcome. In our secondary model restricted to WHIV, both lower maternal and lower gestational age were associated with the composite adverse birth outcome outcome. These findings are broadly consistent with previous literature documenting adverse birth outcomes associated with lower maternal [33, 34] and gestational age at birth [35].
Our results may also differ from other studies because our participants differed from those included in prior studies. Our participants were enrolled from a tertiary hospital, had high ANC attendance, all WHIV reported taking ART (most starting before conception), had a high median CD4 count, and 74% had an undetectable viral load. This suggests that most WHIV were accessing healthcare services, which may have mitigated the potential adverse effects of syphilis and HIV on adverse birth outcomes. Similarly, we observed fewer stillbirths than in prior studies that report rates exceeding 25% [36], even though we observed increased stillbirth among TPPA seropositive than TPPA seronegative women, in line with known associations between stillbirth and syphilis [36], perhaps due to recruitment from a tertiary care hospital.
Our study is among the first in East Africa to document the relationship between dual HIV and TPPA seropositivity (with RPR data for a subset of participants) and adverse birth outcomes. One strength of our study is the large sample size, which includes data from 970 prospective cohort participants and detailed information on risk factors and outcomes. However, despite the large cohort size, our cohort may be too small to detect subtle associations between dual seropositivity and outcomes. There are other potential limitations to our analysis, including our use of TPPA seropositivity as a proxy for syphilis infection, which likely reflects both active and prior infection. Because we were unable to confirm treatment for people reporting syphilis or testing TPPA positive, which has been documented to lower stillbirth and low birthweight risk, our observed findings may under-estimate the true association between active syphilis and stillbirth, because some women with TPPA positivity may have prior treated and thus cured syphilis. We also did not evaluate for congenital syphilis among children, limiting our ability to comment on the transmission of syphilis perinatally and its potential long-term effects in this population. Additionally, recruiting women in early-stage labor may have underestimated the stillbirth rate associated with syphilis, as women who had stillbirth out of hospital at home may not have presented for delivery.
In conclusion, we report a high TPPA prevalence among WHIV in this population delivering at a tertiary hospital in Uganda, higher than previously reported in other studies among WHIV in sub-Saharan Africa. Our results highlight the urgent need for improved prenatal syphilis screening and treatment to enhance maternal and child health outcomes. Interventions to improve screening could include increasing the availability of testing supplies in ANC clinics, expanding training programs for healthcare workers to enhance syphilis diagnosis and management, a global investment in benzathine penicillin manufacturing and supply chain, integrating routine syphilis screening in HIV clinics, and strengthening community outreach programs to raise awareness about the importance of syphilis testing and treatment among women of reproductive age.
ACKNOWLEDGEMENTS
The authors are grateful to the cohort participants and the Mbarara Regional Referral Hospital Maternity Staff, Mbarara University of Science and Technology, MUST Pathology Laboratory, MRRH ISS Clinic, and Kabwohe Clinical Research Center for their partnership in this research.
FUNDING
This work was supported by the Harvard University Center for AIDS Research, an NIH funded program [grant number P30AI060354 to LMB], which is supported by the following NIH Co-Funding and Participating Institutes and Centers: NIAID, NCI, NICHD, NIDCR, NHLBI, NIDA, NIMH, NIA, NIDDK, NINR, NIMHD, FIC, and OAR. The work was conducted with support from the UL1TR002541 award through Harvard Catalyst | The Harvard Clinical and Translational Science Center (National Center for Advancing Translational Sciences, National Institutes of Health) and financial contributions from Harvard University and its affiliated academic healthcare centers. Additional support was provided by the Charles H. Hood Foundation (to LMB), a career development award from the National Institute of Allergy and Infectious Diseases [grant number K23AI138856 to LMB] a mid-career mentoring award from the National Institute of Allergy and Infectious Diseases [grant number K24AI141036 to IVB], the Massachusetts General Hospital Center for Global Health Finish Line Grant (to TMK), and the Burroughs Wellcome Fund/American Society of Tropical Medicine and Hygiene Postdoctoral Fellowship in Tropical Infectious Diseases (to LMB). The sponsors had no role in study design, data collection, analysis or interpretation, writing the report, or the decision to submit the article for publication. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health, Harvard Catalyst, Harvard University, Massachusetts General Hospital, or other funders.
Footnotes
CONFLICTS OF INTEREST
MC, TMK, OB, IVB, MJS, AB, ET, PC, JA, EK, SA, JN, LMB all report no conflict of interest.
REFERENCES
- 1.Hakizimana T, Muhumuza J, Selamo FM, Ishimwe MPS, Kajabwangu R, Jelle OM, Muhumuza J, Kiyaka SM, Nyakato S, Fajardo Y (2023) Prevalence and Factors Associated with Syphilis among Mothers with Missed Opportunities for Antenatal Syphilis Testing in Rural Western Uganda: A Cross-Sectional Study. Int J Reprod Med 2023:2971065. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.World Health Organization Global shortages of penicillin. https://www.who.int/teams/global-hiv-hepatitis-and-stis-programmes/stis/treatment/shortages-of-penicillin. Accessed 23 Apr 2025
- 3.Fang J, Partridge E, Bautista GM, Sankaran D (2022) Congenital Syphilis Epidemiology, Prevention, and Management in the United States: A 2022 Update. Cureus 14:e33009. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Centers for Disease Control and Prevention (2025) Effects of HIV, Viral Hepatitis and STIs on Pregnancy and Infants. In: Pregnancy and HIV, Viral Hepatitis, STDs, & Tuberculosis Prevention. https://www.cdc.gov/pregnancy-hiv-std-tb-hepatitis/effects/index.html. Accessed 23 Apr 2025
- 5.Gomez GB, Kamb ML, Newman LM, Mark J, Broutet N, Hawkes SJ (2013) Untreated maternal syphilis and adverse outcomes of pregnancy: a systematic review and meta-analysis. Bull World Health Organ 91:217–226 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.World Health Organization (2017) Recommendations on syphilis screening and treatment for pregnant women. WHO Guideline on Syphilis Screening and Treatment for Pregnant Women [Google Scholar]
- 7.Oloya S, Lyczkowski D, Orikiriza P, Irama M, Boum Y, Migisha R, Kiwanuka JP, Mwanga-Amumpaire J (2020) Prevalence, associated factors and clinical features of congenital syphilis among newborns in Mbarara hospital, Uganda. BMC Pregnancy Childbirth 20:385. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Masereka EM, Ngabirano TD, Osingada CP, Wiltshire CS, Castelnuovo B, Kiragga AN (2019) Increasing retention of HIV positive pregnant and breastfeeding mothers on option-b plus by upgrading and providing full time HIV services at a lower health facility in rural Uganda. BMC Public Health 19:950. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Li H, Liu J, Tan D, Huang G, Zheng J, Xiao J, Wang H, Huang Q, Feng N, Zhang G (2020) Maternal HIV infection and risk of adverse pregnancy outcomes in Hunan province, China. Medicine (Baltimore) 99:e19213. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Yeganeh N, Watts HD, Camarca M, et al. (2015) Syphilis in HIV-Infected Mothers and Infants: Results from the NICHD/HPTN 040 Study. Pediatr Infect Dis J 34:e52–e57 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.González R, Rupérez M, Sevene E, et al. (2017) Effects of HIV infection on maternal and neonatal health in southern Mozambique: A prospective cohort study after a decade of antiretroviral drugs roll out. PLoS One 12:e0178134. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Bruce-Brand C, Wright CA, Schubert PT (2021) HIV, Placental Pathology, and Birth Outcomes—a Brief Overview. The Journal of Infectious Diseases 224:S683–S690 [DOI] [PubMed] [Google Scholar]
- 13.Gilbert L, Dear N, Esber A, et al. (2021) Prevalence and risk factors associated with HIV and syphilis co-infection in the African Cohort Study: a cross-sectional study. BMC Infect Dis 21:1123. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Lynn W, Lightman S (2004) Syphilis and HIV: a dangerous combination. The Lancet Infectious Diseases 4:456–466 [DOI] [PubMed] [Google Scholar]
- 15.Shava E, Moyo S, Zash R, et al. (2019) High rates of adverse birth outcomes in HIV and syphilis co-infected women in Botswana. J Acquir Immune Defic Syndr 81:e135–e140 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Tukei VJ, Hoffman HJ, Greenberg L, et al. (2021) Adverse Pregnancy Outcomes Among HIV-positive Women in the Era of Universal Antiretroviral Therapy Remain Elevated Compared With HIV-negative Women. The Pediatric Infectious Disease Journal 40:821. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Schmid G Economic and programmatic aspects of congenital syphilis prevention. Bull World Health Organ. 2004; 82(6):402–409. [PMC free article] [PubMed] [Google Scholar]
- 18.Watson-Jones D, Gumodoka B, Weiss H, et al. Syphilis in pregnancy in Tanzania. II. The effectiveness of antenatal syphilis screening and single-dose benzathine penicillin treatment for the prevention of adverse pregnancy outcomes. J Infect Dis. 2002; 186(7):948–957. [DOI] [PubMed] [Google Scholar]
- 19.Moyo E, Moyo P, Murewanhema G, Mhango M, Chitungo I, Dzinamarira T (2023) Key populations and Sub-Saharan Africa’s HIV response. Front Public Health 11:1079990. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.McDiehl RP, Boatin AA, Mugyenyi GR, Siedner MJ, Riley LE, Ngonzi J, Bebell LM (2021) Antenatal Care Visit Attendance Frequency and Birth Outcomes in Rural Uganda: A Prospective Cohort Study. Matern Child Health J 25:311–320 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Bebell LM, Siedner MJ, Ngonzi J, Le MH, Adong J, Boatin AA, Bassett IV, Roberts DJ (2020) Chronic Placental Inflammation Among Women Living with HIV in Uganda. J Acquir Immune Defic Syndr 85:320–324 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22.Harris PA, Taylor R, Thielke R, Payne J, Gonzalez N, Conde JG (2009) Research electronic data capture (REDCap)--a metadata-driven methodology and workflow process for providing translational research informatics support. J Biomed Inform 42:377–381 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.Kawungezi PC, AkiiBua D, Aleni C, et al. (2015) Attendance and Utilization of Antenatal Care (ANC) Services: Multi-Center Study in Upcountry Areas of Uganda. Open J Prev Med 5:132–142 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24.Haule A, Msemwa B, Mgaya E, Masikini P, Kalluvya S (2020) Prevalence of syphilis, neurosyphilis and associated factors in a cross-sectional analysis of HIV infected patients attending Bugando Medical Centre, Mwanza, Tanzania. BMC Public Health 20:1862. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25.Mussa A, Jarolimova J, Ryan R, Wynn A, Ashour D, Bassett IV, Philpotts LL, Freyne B, Morroni C, Dugdale CM (2024) Syphilis Prevalence Among People Living With and Without HIV in Sub-Saharan Africa: A Systematic Review and Meta-Analysis. Sexually Transmitted Diseases 51:e1. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 26.Hamill MM, Mbazira KJ, Kiragga AN, Gaydos CA, Jett-Goheen M, Parkes-Ratanshi R, Manabe YC, Nakku-Joloba E, Rompalo A (2018) Challenges of Rapid Plasma Reagin Interpretation in Syphilis Screening in Uganda: Variability in Nontreponemal Results Between Different Laboratories. Sex Transm Dis 45:829–833 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 27.Ministry of Health, Uganda (2022) Essential Maternal and Newborn Clinical Care Guidelines for Uganda.
- 28.Dadzie LK, Agbaglo E, Okyere J, Aboagye RG, Arthur-Holmes F, Seidu A-A, Ahinkorah BO (2022) Self-reported sexually transmitted infections among adolescent girls and young women in sub-Saharan Africa. Int Health 14:545–553 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 29.Adong J, Musinguzi N, Ngonzi J, Haberer JE, Bassett IV, Siedner MJ, Roberts DJ, Hahn JA, Bebell LM (2024) Effects of Maternal HIV Infection and Alcohol Use in Pregnancy on Birth Outcomes in Uganda. AIDS Behav 28:805–810 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 30.Murray C, Portwood C, Sexton H, Kumarendran M, Brandon Z, Kirtley S, Hemelaar J (2023) Adverse perinatal outcomes attributable to HIV in sub-Saharan Africa from 1990 to 2020: Systematic review and meta-analyses. Commun Med (Lond) 3:103. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 31.Xiao P-L, Zhou Y-B, Chen Y, Yang M-X, Song X-X, Shi Y, Jiang Q-W (2015) Association between maternal HIV infection and low birth weight and prematurity: a meta-analysis of cohort studies. BMC Pregnancy and Childbirth 15:246. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 32.Rebnord T, Mmbaga BT, Sandøy IF, Lie RT, Mchome B, Mahande MJ, Daltveit AK (2023) Time trends in perinatal outcomes among HIV-positive pregnant women in Northern Tanzania: A registry-based study. PLOS ONE 18:e0289740. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 33.Ahinkorah BO (2021) Under-5 mortality in sub-Saharan Africa: is maternal age at first childbirth below 20 years a risk factor? BMJ Open 11:e049337 [Google Scholar]
- 34.Ahinkorah BO (2021) Maternal age at first childbirth and under-five morbidity in sub-Saharan Africa: analysis of cross-sectional data of 32 countries. Arch Public Health 79:151. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 35.Neggers YH (2018) Gestational Age and Pregnancy Outcomes. Pregnancy and Birth Outcomes. 10.5772/intechopen.72419 [DOI] [Google Scholar]
- 36.Kuznik A, Habib AG, Manabe YC, Lamorde M (2015) Estimating the public health burden associated with adverse pregnancy outcomes resulting from syphilis infection across 43 countries in sub-Saharan Africa. Sex Transm Dis 42:369–375 [DOI] [PMC free article] [PubMed] [Google Scholar]