The benefits of a cardiac resynchronization therapy (CRT) implantation are known in severe heart failure and its implantation may also be considered during pregnancy to ensure safe pregnancy and delivery for both the mother and the fetus. This study on a patient case aimed to estimate the absorbed dose (AD) to the fetus during the CRT implantation of 21st week of the pregnant woman. AD measurement was done using anthropomorphic phantom, radiophotoluminescence dosemeters and Monte Carlo simulation utilizing kerma area product (KAP) of the procedures. The measured AD for a phantom’s uterus and heart was 0.116 and 14.7 mGy with total KAP of 27.9 Gycm². The estimated actual AD to the fetus and the mother’s heart was 0.004 and 1.2 mGy, with total KAP of 1.5 Gycm². The dose to the fetus can be minimized with the optimized procedure.