PURPOSE: To present a methodology for the estimation of conceptus dose prior to the completion of a medically required and justified interventional radiology or cardiology procedure. MATERIALS AND METHODS: The free of charge National Cancer Institute dosimetry system for Radiography and Fluoroscopy dose calculator tool was adopted to estimate organ absorbed doses through Monte Carlo radiation transport. A procedure was developed for required data collection ahead of the study for dose estimation. This information was used to build the input to the dose calculator tool. Data inclusion and assumption considerations were discussed for final report drafting and communications with the intended interventionalist. RESULTS: Implementation of this methodology has been used to support pre-procedural decision making for our institutions interventionalists. Pre-procedural conceptus dose estimates permitted an educated assessment of the risk-benefit of the potential radiation exposure to the patient and conceptus against the medical necessity of the procedure. It can also guide the real-time dose monitoring during the procedure when a maximum permissible cumulative air kerma (CAK) level is determined before the procedure. CONCLUSION: A methodology for the estimation of conceptus dose prior to the completion of an interventional fluoroscopy procedure was developed. Due to the prospective nature of this dose estimation methodology, the model relies heavily on professional experience and, when available, quantitative metrics.