Mars-born children
Eventually, children will be born on Mars, the next generation of Mars colonists.
Effects of gravity on growth
Experiments in zero gravity show that animal embryos do not develop properly in zero-g. Mars has 0.38 gravity, so, even if the said child was not deformed, that child would develop and grow in 0.38 gravity. So, the child may be extremely healthy by Mars standards, but severly weak by Earth standards.
Immune systems
Children growing up on Mars will not come in to contact with microbes as Earth children would. Thus, it is import to vaccinate them to boost their immune systems.