[en] Doses were calculated by means of Monte Carlo methods in a three months pregnant woman's internal organs on account of the radioiodine captured by her thyroid as well as 1 m of the gland. A three-dimensional model of the woman's body was used, and the photons of radioiodine were isotropically transported by means of Monte Carlo from the thyroid through all the body, and the dose adsorbed by her body was calculated. Also, the Kerma (K) in the air was determined, and the environmental dose equivalent to 1 m of the gland (H*(10)). Two activity factors to dose were determined; they are also called Gamma Factors, which allow estimating the dose that the patient produces to people surrounding her. There were found that, from the gamma radiation that emits the 131I in the thyroid, the thymus receives the highest dose while the uterus is the organ that receives the lowest dose. The determined gamma factors were: ΓKAir = 52.06 μGy-m2-h-1-GBq-1, y ΓH*(10) 67.72 μSv-m2-h-1-GBq-1. The distribution of the dose adsorbed by the internal organs is attributed to the relative distance between the thyroid and the other organs, to the inter-organs armor, to its size and to its elemental composition. Factors ΓKAire y ΓH*(10) allow estimating the exposure that the patient produces on the personnel around her. With this, the nuclear medical, the physician medical or the responsible of radiological security in the hospital can give more precise instructions about people behavior around the patient