Time to initiation of antenatal care and its predictors among pregnant women across 35 Sub- Saharan African Countries (2011–2024): A multilevel mixed-effects acceleration failure time model of multination population survey data

Background Despite the well-established link between delayed initiation of antenatal care (ANC) and negative pregnancy and childbirth outcomes, a substantial proportion of women in sub-Saharan Africa continue to begin ANC late in their pregnancies. The previous studies failing to incorporate the most current information, confined to a single country or small number of nations and employed statistically flawed proportional hazard models with violated assumptions compromising the reliability of the conclusions. Therefore, this study aimed to investigate the timely initiation of ANC and its determinants among pregnant women in 35 Sub-Saharan African countries by utilizing mixed-effects acceleration failure time model based on the most recent (2011–2024) Demographic and Health Survey data. Methods A retrospective follow-up study using secondary data from the Demographic and Health Surveys of 35 sub-Saharan African countries conducted between 2011 and 2024. A total weighted sample of 222, 866 women aged 15–49 years who had Antenatal care visits during their current or most recent pregnancy within the 5 years prior to the survey were included in the analysis. Descriptive and inferential analyses were performed using STATA 17. A multistage stratified cluster sampling technique was employed. The Kaplan-Meier (KM) method was used to estimate time to first antenatal care visit. A multilevel mixed-effects Weibull acceleration failure time survival model was applied to determine predictors. Model adequacy was assessed by using the proportional hazard assumption using scaled Schoenfeld residuals. The adjusted acceleration factor with 95% confidence intervals were used to indicate statistical significance and the strength of associations. Model comparison was evaluated by model statistical summary such as Akaike's Information Criterion (AIC), Bayesian Information Criterion (BIC), log-likelihood (LL), and deviance (-2*LL). Result In this study, the estimated mean survival time for pregnant women to initiate their first ANC visit across 35 sub-Saharan African countries was 6.9 months (95% CI: 6.89–6.92). Women age 15–24 (AAF = 0.88; 95% CI: 0.86, 0.90), being rural residence (AAF = 0.91; 95% CI: 0.90, 0.93), women with no formal, primary, and secondary education respectively (AAF = 0.95, 95% CI: 0.92, 0.98; AAF = 0.84, 95% CI: 0.82, 0.87; AAF = 0.83, 95% CI: 0.80, 0.85), home delivery (AAF = 0.82; 95% CI: 0.81, 0.83), single marital status (AAF = 0.96; 95% CI: 0.95, 0.98), being not exposed to mass media (AAF = 0.90; 95% CI: 0.88, 0.91), poor and middle wealth index respectively (AAF = 0.96; 95% CI: 0.94, 0.98; AAF = 0.92; 95% CI: 0.90, 0.94), multiparous (AAF = 0.91; 95% CI: 0.89, 0.93), grand multiparous (AAF = 0.79; 95% CI: 0.77, 0.80), and low community Antenatal care utilization (AAF = 0.39; 95% CI: 0.38, 0.40) were predictors of time to first ANC visit. Conclusion The timely initiation of the antenatal care (ANC) in the first trimester remains a significant challenge across 35 sub-Saharan African countries, with a prevalence of only 41.5% and a mean delay of nearly seven months before the first visit. This low rate was influenced by sociodemographic, obstetrics and community level factors including young maternal age, rural residence, home delivery, lower educational status and wealth index, multi and grand multiparous, being not exposure to mass media and low community ANC utilization. Addressing this critical ga requires targeted, multi-level interventions such as adolescent-friendly services, community education, financial support, and expanded healthcare access. Strengthening media outreach and integrating ANC promotion in to existing reproductive health programs are essential to shift social norms. Future research must incorporate health system and country level variables and employ longitudinal designs to establish casualty and inform more effective policies aimed at making timely ANC initiation a cornerstone of maternal health in the region.