Standard, Population & Customised fetal size charts 8 – height

Customisation on maternal height

If there is any justification for customising fetal size charts, this is likely to be it. Height is objective, easy to measure, does not vary by gestational age, and is not influenced much by current nutrition, smoking or drug abuse. And taller mothers do tend to have larger babies.

If maternal height was largely due to benign genetic variation, with healthy tall mothers having larger healthy babies, and healthy shorter mothers having healthy smaller ones – remember the Shire horses and Shetland ponies- it would improve detection of pathology. But it is not.

Height is also closely related to parental and early life nutrition, and to health in adult life. Over the last 100 hundred years average heights have increased much faster than they plausibly could have by natural selection (review here). The cause is almost all better nutrition, reduced infections and other environmental improvements. Over this period perinatal mortality has fallen steeply. Even within modern populations short maternal height is clearly associated with stillbirth (table 1 here).

We don’t need to assume that short height causes stillbirths to make customisation inappropriate. If height is associated with some third factor which causes the adverse outcomes it would still be an inappropriate measure on which to customise.

Next gender and parity (click here)

Jim Thornton