Besides chemical testing, thermographic imaging is a possible method to determine pregnancy in some animals. Hilsberg (2001) defined the unilateral warming at the end of a pregnancy, caused by the metabolizing fetus and the uterus near the outer skin, as the pregnancy field. Its appearance was observed in various species at the end of the gestation period. No studies were yet carried out to investigate the changing of thermal patterns during pregnancy. This study monitored the thermographic changes of one pregnant babirusa (Babyrousa babyrussa) sow and one babirusa male by taking thermal images once a week from the estimated 3rd pregnancy week until parturition in the 23rd pregnancy week. Images were searched manually for heat areas correlated to pregnancy as well as analysed automatically for median and maximum temperatures of the animal's side. Additionally, the locations of all pixels, which were not more than 2 K below the maximum temperature, were evaluated. In the female, there was a positive correlation between maximum temperatures of left and right side to pregnancy weeks (R = 0.61, R = 0.66, respectively; p < 0.05). The female's median temperatures and all temperatures of the male were not correlated to pregnancy weeks. Differences between median and maximum temperatures were significantly different during the 2nd, and 3rd trimester in the female, but not in the male. Temperature differences between 1st and 2nd trimester were not significant in both animals. The location of the warmest areas in the female shifted from thorax and flank to be mainly localised on the teats. In the male, the warmest areas remain localised on thorax and flank. No distinct pregnancy field was observed, but the warming of the teats could be seen in the images and the evaluated data. The teats are less insulated in most animals. Contraindications for thermal imaging like insulation could therefore become less important, allowing thermal pregnancy diagnosis for a larger range of animals than before. Based on these findings we suggest that the warming of the teats could be used for thermal pregnancy diagnosis when a pregnancy field is not observable.