Thanos killed half of all living creatures so the other half doesn’t die from lack of resources, but Tony is going to die exactly because of lack of resources in the trailer
This phenomenon is called Lithopedion, which means “stone baby”. It occurs after an abnormal pregnancy and death of the fetus, when for some reason it is retained by the mother’s body. The fetus is too big to be reabsorbed, so it gets calcified by the mother’s body, to shield her from the dead tissue. This is extremely rare (Source)