Ultrasound Index -- Dozens of extremely high-quality ultrasound images

First Trimester :

By the end of the first month after conception, a simple functioning circulatory system has developed in the embryo. The spinal cord is closed and the embryo is 1/6 inch long (4mm). At the end of the second month the cardiac valves and four chambers of the heart are established and functioning.

Nervous system development has begun, and so has motor activity. In month three, the fetus jerks its body and flexes its tiny legs and arms. Weight is 3/4 ounce (21 grams), about the same as a letter.

        a)  First Trimester - Uterus with Gestational Sac 

Uterus with gestational sac. Calibration marks indicate this embryo is nine millimeters in length, under 1/2 inch, which is six-weeks normal growth.

          b) First Trimester - Fetus at Eight Weeks

Fetus at eight weeks with yolk sac, a ball-shaped blood cell factory, clearly visible. Early formations of the limbs (limb buds) are seen.

         c) First Trimester - Fetal Profile at 12 Weeks

Fetal profile at 12 weeks. Note the development of the facial features and the hand approaching the mouth.

        d) First Trimester - Movement of the Fetal Heart

This graph (M-mode) clearly shows movement of the fetal heart.

Second Trimester :

During the fourth month the fetus reaches almost 6 inches (15cm) in length. Arms and hands are fully shaped with fingernails. Feet and legs are fully molded, and hair has already started to appear. In the fourth and fifth month the fetus begins reacting to sound, and hair becomes courser and colored. In the sixth month the fetus is over 12 inches (30 cm) long. The thumb is actively involved in grasping. The inner ear is structurally capable of functioning.

            a) Second Trimester - Profile of a Fetus at Four Months 

Profile of a fetus at four months. This face is approximately 1 1/2 inches (4cm) long.

  

             b) Second Trimester - Fetal Arm

The fetal arm with the major arteries (radial and ulnar) clearly delineated.

          c) Second Trimester - Fetal Urination 

The sensitivity of color Doppler to the movement of fluids captures fetal urination.

        d)   Second Trimester - Five-month Fetus (lungs, liver and bowel)

Subtle differences in tissue textures allow the fetal lungs to be distinguished from the neighboring liver and bowel in this five-month fetus.

        

Third Trimester :

In the seventh month taste has probably been established. From now until term, fetal length increases from approximately 13 to 20 inches and weight nearly triples. By the eighth month lungs are maturing and the fetus continues to practice the motions of breathing. On the average, delivery occurs at 40 weeks, although there is a normal variation of two weeks on either side (38-42 weeks).

              a) Third Trimester - Fetal Brain

The fetal brain showing the intersection of the major blood vessels (circle of Willis) and surrounding structural anatomy.

             b) Third Trimester - Flow of Blood Through the Placenta

Color highlights the flow of blood through the placenta.

           c) Third Trimester - It's a Girl!

It's a girl! Depending upon the position of the fetus, ultrasound can aid in the determination of gender.

        d) Third Trimester - Umbilical Cord

A normal umbilical cord appears as two arteries and a vein in an ultrasound image.