ABC News: Ma'ayan Rosenzweig

There are many fruits and veggies that have provided a useful reference for the size of the royal fetus, now in its 18 th week of development. A bell pepper, apple and tomato come to mind. However, at roughly 5-and-a-half inches long and 7 ounces in weight, a sweet potato seems the best comparison right now.

Lots of developments happening at this point.

With the ears now in their final position, the bones in the inner ear canal nearly formed and the nerve connections between the ears and the brain fully matured, the baby can now hear Kate's heart beating and the blood flowing through the umbilical cord. The taste buds have also sprung to life.

If HRH-to-be is a boy, he now has a prostate. If a girl, she has a uterus. Regardless of the sex, the baby can now yawn, stretch and make facial expressions. It's strong enough, big enough and active enough that Kate may feel the occasional kick or flip in her tummy.