The first trimester is a time of great changes in your body and to your baby's developmental process. As you reach week 10 of your pregnancy, your baby begins to form the attributes that result in a more human-like appearance. Developmentally, the 10th week brings about changes your baby's organs, limbs, face and head as well as beginning a time of rapid development and growth as you approach the second trimester.
Size
Your baby is the size of a small kumquat or prune by 10 weeks, which is about an inch to an inch and a half in length from crown to rump. Although your baby is small, he's mighty, making you feel nauseous, tired and hungry. Your baby's head makes up roughly half the size of his body, with a bulging forehead and small torso. Your uterus is also growing to adapt to the size of your baby, moving from the size of a small pear before you were pregnant to resembling the size of a grapefruit. Your baby will double in size by the end of the first trimester, growing to three inches around week 12.
Vital Organs
Week 10 completes some of the most important parts of development for your baby: the vital organs. Your baby's kidneys, intestines, brain and liver finish developing and even begin to function, though not independently of you. Your baby begins to create red blood cells, but her organs will continue to develop until birth. Your baby also already has genitals, though it's likely impossible to see on an ultrasound; you'll need to wait another 5 to 10 weeks before you'll know your baby's sex.
Eyes, Toes and Spine
If your doctor orders an early ultrasound, you'll be able to see your baby's spine clearly, as it shows through your baby's currently transparent skin. What you won't be able to see is other changes in his body. By 10 weeks, your baby will have tiny arms, fingers and fingernails. His arms curl toward his body and meet in front of the heart, giving your baby a curled appearance. The buds that will one day become teeth have developed, though they won't make their appearance until around 6 months of age.
Overall Appearance
Your baby is starting to look more like a person. While once a simple mass of cells, by 10 weeks your baby's head, neck, spine, arms and legs have formed. Your baby's bones and cartilage are forming and soon the joints at the elbows and knees will make their appearance. This will in turn cause more movement, which you should be able to feel between 16 and 20 weeks gestational age.
