The correct answer is: "The Nazis wanted to get rid of those incapable of hard labor".
From the point of view of the nazis, people who were deported to camps were already considered dispensable, subhumans who contaminated the superior Aryan race: Jews, gypsys, communists, homosexuals, disabled, etc. But Germany was fighting a war and, although many of the deported people were executed straightaway, others were used for hard labor, specially to produce military equipment. Pregnant women, weak and sick individuals were considered useless for hard labor and for this reason they were the first to be executed (anyway they intended to execute the others or many died working too).