Did we know fetus sizes before ultrasounds? If so, how?

Question

How did we figure out the exact growth rates of developing fetuses? Also, how do we know which parts of them develop when? Even if the answer is ultrasounds, how could doctors tell? Ultrasounds are so distorted and grey...

Answer 1

Growth rate and development was learned from miscarried fetuses where the date of conception was known, and animal studies.

Ultrasounds, when you know how to read them, show a lot of detail.

Answer 2

Ultrasounds now are amazingly clear.  They used to look like static (to me).  These days you can see facial features and all sorts of detail.

In the distant past, they looked at miscarried or aborted fetuses.

Answer 3

If the mother dies or aborts the baby docotrs can inspect the fetus. If you do this enough times you'll see all the different stages of growth

Answer 4

Measurements from aborted and stillborn fetuses gave an approximation of fetal size at a particular stage, but spontaneously aborted and stillborn fetuses often had an abnormal growth rate. So it was an approximation. Still, it was a well-studied field, and embryology books from the 1950's were reasonably accurate as to organogenesis.

The growth of a live fetus in the mother's womb could be estimated by measuring the height of the fundus of the uterus above the pubis. But obviously, this varied with the size of the mother as well. Then there were the "maneuvers of Leopold" by which the OB palpated the fetus inside the womb. Some of those old timers were very good at determining fetal size. Finally, there were x-ray measurements, but I have forgotten the technical term for this.

Nothing compares to the accuracy and ease of use of ultrasound. Marvelous invention!