By week 19 of your twin pregancy, baby girls' genitals are beginning to form.  For baby boys, their genitals are becoming more obvious.

At this stage, your twins measure about 5.2 - 6 inches long. 

Vernix, the protective creamy white substance begins to from around babies' bodies.

As your babies swallows amniotic fluid, their kidneys start to produce urine!

Your twins permanent teeth buds are forming at this time as well.