13 Weeks...according to Dr. Goo.gle

• The fetus has grown to about 3 inches (8cm) long.
• Weight approximately 1 ounce (25 grams).
• Bone is beginning to replace cartilage and the ribs are appearing.
• The nose and chin are well defined.
• Movements can be measured.
• The child will begin to learn to suck its thumb.
• The child can open and close its mouth.
• The external genitalia are well defined making it is possible to determine the baby's gender.

Your baby is now producing insulin the hormone that controls their blood glucose. The fetus is now 3 inches long and weighs about an ounce. The baby's unique fingerprints are already in place. The muscles lengthen and become organized. You can't feel it yet, but your baby can move in a jerky fashion, flexing the arms and kicking the legs. Your uterus has grown quite a bit. You can probably feel its upper edge above the pubic bone in the lowest part of your abdomen, about 4 inches (10cm) below your bellybutton.

At 13 weeks, your uterus fills your pelvis and starts growing upward into your abdomen. It feels like a soft, smooth ball. Soon you will start feeling the first flutters of the unborn child kicking and moving within. The first three months were period of rapid development, next three months will be period of rapid growth. Baby quadruples weight during the 4th month. Your baby is about 2.91 inches (7.4cm) and weighs around 0.81 ounce (23gm).