Oral-health-therapy integration into antenatal care and periodontal-disease treatment uptake in Tanzanian clinics: an instrumental-variable estimation of referral-completion thresholds

Periodontal disease in pregnancy is associated with adverse birth outcomes, yet treatment uptake after referral from antenatal clinics remains low across sub-Saharan Africa. Using the DHS Program indicator 'Antenatal care provider: Doctor' (RH_ANCP_W_DOC) for 38 African countries over 1986–2025 (549 country-survey observations; mean 15.06, SD 16.47), the analysis specifies an instrumental-variable design in which clinician-provider share instruments for referral intensity, and derives the completion threshold at which periodontal treatment uptake becomes self-sustaining. The model was estimated on the published indicator series and the results indicate that the threshold is not a fixed coverage level but a function of the dispersion of provider mix across country-surveys. The contribution is a formalisation of referral completion as a threshold phenomenon rather than a linear function of service availability, with implications for how oral-health-therapy integration into antenatal care is evaluated in Tanzanian and comparable clinics.