By the thirteenth week your baby is about 8 inches long and about 25 grams. Your baby has a well-defined chin and a nose. Cartilage structure of bone continues to calcify to form mature bones. Your baby opens and closes its mouth often. It learns to suck its thumbs. It swallows the “water” in its water bag. Your baby’s fingers are well developed and they contain unique fingerprints now. Limbs lengthen and strengthen because muscles organize to resemble the new born configuration. Your baby moves jerkily. These jerky movements are visible in ultrasound scan as kicks. It may be possible to distinguish between male and female babies via ultra sound scan after thirteen weeks. First three months of your baby’s life inside you showed rapid development and differentiation. From now on your baby will spend a period of very rapid growth.
Now that you are past the period of continuous nausea and vomiting, you might not even feel that you are pregnant. Only your growing tummy assures you of the fact. You do not feel your baby move yet. Your womb feels like a smooth round mass coming up from below.
Your bladder is just in front of your womb. So your bladder cannot fill as much as before because of the enlarging womb. So you feel that you need to pee every so often. This constant peeing will go on for a few weeks until your womb grows a bit more and moves up away from the pelvis.
You are susceptible to urine infections these days. So make sure you drink a lot of water. Try to avoid long trips because you will invariably would be looking for a loo on the way.