This week, the babies may have reached 15 cm from crown to rump (but different sites seem to be reporting different measurements!), and they can both feel and hear. Admittedly at the moment, all they can hear is my heartbeat and the flow of my digestive system (poor them!) but soon they will be able to detect noise outside the womb and identify your voice! I'm sure this is going to please Chris lots as he has been talking to them for a few weeks now! This means I'm going to get more nights where he is pressed up against my belly speaking at them!
Their skeleton started off as rubbery cartilage, but it is now starting to toughen up; and their limbs are lengthening, their legs are now longer than their arms and they have far more bones than an adult, but many of these will fuse together before birth. They are now looking ever more like a proper human being. Now that they are roughly in proportion, their body will grow at a slower rate. Most of their weight gain from now on will be fat.
The umbilical cord, pumped entirely by their little hearts, can now circulate up to 28 litres (50 pints) of fluid a day, taking food and oxygen to each of them (I have two placentas) and removing waste products.
The development of their digestive system is well underway now too. Their intestines are now anchored inside their abdomens, and their digestive glands are growing. Their immune system is also beginning to mature, ready for life outside the womb.
As for me, I'm getting bigger and bigger! One site said my uterus should be the size of a honeydew melon - well it would be if I was having just one! but as I'm having two it's twice that size and don't I know it!
Here is a picture taken last week at about 17.5 weeks: