Tall Girl

Moreover, the health of a mother throughout her life, especially during her critical periods, and of course during pregnancy, has a role. A healthier child and adult develops a body that is better able to provide optimal prenatal conditions. The pregnant mother's health is important as gestation is itself a critical period for an embryo/fetus, though some problems affecting height during this period are resolved by catch-up growth assuming childhood conditions are good. Thus, there is an accumulative generation effect such that nutrition and health over generations influences the height of descendants to varying degrees.
The age of the mother also has some influence on the her child's height. Studies in modern times have observed a gradual increase in height with maternal age.
The precise relationship between genetics and environment is complex and uncertain. Human height is 60%-80% heritable, according to several twin studies and has been considered polygenic since the Mendelian-biometrician debate a hundred years ago. The only gene so far attributed with normal height variation is HMGA2. This is only one of many, as each copy of the allele concerned confers an additional 0.4 cm (0.16 in) accounting for just 0.3% of population variance.