By the end of the third month of pregnancy, or first trimester, morning sickness may finally be fading and the later discomforts of pregnancy haven't yet made an appearance. Unless you've had previous pregnancies, you're probably barely showing much in the way of a baby bump. But inside the womb, big changes are occurring daily; at the end of this time period, all your baby's major organs are already in place and he's easily recognizable as a member of the human race.
A 3-month-old fetus is roughly 3.5 inches long, or about the size of a domino playing piece. From this point, your tiny baby will continue to grow about a quarter inch per week. His head is still disproportionately large, comprising half of his size. By the twelfth week of pregnancy, your baby weighs approximately 45 grams, or 1.5 ounces.
Your baby's intestines began to grow so fast in your third month that they protrude into the umbilical cord. In week 12, they'll settle back into the abdominal cavity. Her heart is beating at around 150 beats per minute, and her heartbeat is usually first detected at the 10-week mark by your obstetrician and his fetal Doppler. If Most all of her other organs and tissues are already developed by the end of the third month. Teeth begin to form under gums.
While your tiny baby still doesn't look like a newborn, his arms, legs, fingers and toes are all fully developed, right down to the fingernails. His arms are now relatively proportionate to his overall length. His face looks more human. Although his ears are still pinned quite tightly against his head, his eyes have moved closer together on his face. His eyelids are fully formed over his eyes, which will remain closed until around the 25th week of pregnancy. His skin is very thin and translucent.
While internal genitalia differentiate earlier the external genitalia don't differentiate until around week 12. A fetal ultrasound might be able to determine your baby's sex around this time, if your baby cooperates.
Your baby floats freely in your uterus and can move his arms and legs by the 12-week mark, although unless you're carrying twins or are very sensitive, you won't feel it until after 16 weeks. Her fingers and toes can curl, and her mouth can suck and clench. She's beginning to exhibit some of the instinctual reflexes she'll have when born, like automatically sucking for food.