Soon after learning about a pregnancy, expectant parents often wonder what their unborn child looks like. Although a new embryo is too small to see in an ultrasound, science and technology can give an idea about what the embryo looks like and how it is developing. As an unborn baby grows inside the womb, ultrasound technology can show the baby's growth and development, and parents can get an idea of the baby's size and features.
Fertilization to 4 Weeks
At the time of fertilization, there is only a microscopic egg, smaller than a poppy seed. The egg divides to become a small cluster of cells that travels down the fallopian tube and implants into the lining of the uterus. The cells then split into two halves that become the embryo and the placenta. At about 4 weeks gestation, the embryo is multilayered. The layers will begin developing and become the organs, nervous system, hair and skin. The embryo will not be visible on an ultrasound screen, but the amniotic sac and developing yolk sac may be visible.
5 to 12 Weeks
Between 5 and 12 weeks gestation, the unborn baby grows from being the size of an orange seed to the size of a plum. She looks like a tadpole with a tail at around 5 weeks, and the heartbeat may be visible on an ultrasound as a tiny blinking light. At around 8 weeks, the baby's tail will be almost gone. Her fingers and toes are webbed at around this stage, and she is beginning to look more like a baby with lips, eyelids, legs, a nose, a jaw, cheeks and a distinctive back. The legs have indentations that will become the knees and ankles, and the elbows are beginning to bend. Her heart, circulatory system, kidneys, liver and lungs are all developing as well. The baby grows at the rate of about 1 mm a day in spurts that occur all over the body.
13 to 20 Weeks
Between 13 and 20 weeks gestation, an unborn baby goes from being the size of a peach to the size of a melon. The head is oversized at this stage and the baby is covered in a coating called "vernix caseosa" that warms and protects him from the amniotic fluid he is floating in. His eyes and ears are in place, although his eyes are still sealed closed. He is able to wiggle his fingers and toes, and the mother may feel movement during this stage. He has his own set of distinctive fingerprints as well. An ultrasound will show many of his distinctive features, and gender will be visible around 20 weeks.
21 to 30 Weeks
At 21 weeks gestation, an unborn baby is about the length of a large banana. By 30 weeks, she weighs over 3 lbs. Her transparent skin means that her organs and bones are visible, and her fully formed face has eyelashes, eyebrows and hair. Her hair is white at this stage because its pigment has not yet developed. Her nasal nostrils are opening and she can blink, cough, suck, dream and practice breathing. Her head will typically be facing downward in the birthing position. She can perceive dark and light and may be able to taste things through the amniotic fluid. She will begin shedding the hair that covers her body, and an ultrasound will show her features and activities.
31 to 40 Weeks
Between 31 to 40 weeks gestation, most of the development necessary for an unborn baby is complete. He weighs approximately 5 lbs. at about 34 weeks gestation, and all that is necessary before delivery is for the baby to gain weight. His nails have developed on the tips of his fingers and toes, and his skin is becoming less transparent as fat accumulates under the skin. His senses of taste, touch, hearing, sight and smell are developing. His organs are almost fully developed and growth will continue until delivery.
