NORMAL ANATOMY – WEEKS 10-14

• CRL reaches 40mm.

Amnion - Normal appearance at 12 wks

• CNS:
• Partition of ventricles and rapid growth.
• Lateral ventricle contains the echogenic choroid plexus.

• Falx cerebri can be seen dividing the hemispheres.

• Prominent choroids plexus that completely fills the ventricle.

• Cerebellum

• Limb movement apparent (upper extremity followed by lower extremity).

2D images of hands and feet at 11 wks GA
3D feet at 11 wks GA	3D hands at 11 wks GA

• Stomach, urinary bladder and kidneys can be occasionally seen.
• Normal physiological herniation of bowel
• Fetal heart.

EXAMINATION OF THE FOUR-CHAMBER HEART

AT THE 11-14 WEEK SCAN

• At 12–13 weeks of gestation, the four-chamber view can be examined successfully by transabdominal ultrasound in 76% of the cases and transvaginally in 95% (1).

· Bronshtein et al. (2) reported that the diameters of the two ventricles were similar and increased linearly with gestation from:

o 1.5 mm at 11 weeks

o 3 mm at 14 weeks

o Diameter of the heart was about one-third that of the chest and the ratio did not change with gestation.

· Blaas et al. (3) examined the ratio of the heart diameter to that of the abdomen and reported a decrease with gestation from:

o 51% at 8 weeks

o 42% at 12 weeks.

Visualization of the four-chamber view of the heart at ultrasonography at 10–14 weeks of gestation (weeks of gestation)
Reference	10 wks	11 wks	12 wks	13 + 14 wks
2	-	16%	36%	90%
4	0%	30%	90%	100%
5	27%	58%	71%	73%
6	-	80%	93%	100%

Video clip of fetal heart - four chamber view - 12 wks Aortic arch – 12 wks of gestation

EXAMINATION OF THE REST OF THE HEART AT 11-14 WEEKS

• Mitral and tricuspid valves - Dolkart and Reimers (4) reported that the earliest defined cardiac structures visible were the mitral and tricuspid valves.
• At 10 weeks, they were seen in 25% of cases.
• At 12 weeks they were seen in 90% of cases.
• At 13–14 they were seen 100% of cases.
• The five-chamber, aortic arch and ductus arteriosus views were first seen in some fetuses from 12 weeks but in the majority, only at 14 weeks.
• The aortic root in short-axis projection and the left ventricle in long-axis view could be imaged in 70% and 40% of fetuses, respectively by 12 weeks.
• Aortic and pulmonary valves were first visualized at 12 weeks in 20% of the cases.
• Visualization of the four-chambers, aorta, pulmonary artery and pulmonary veins (Johnson et al.) was possible in:
• 0% at 10–11 weeks.
• 31% at 12 weeks.
• 43% at 13 weeks.
• 46% at 14 weeks (5).
• Gembruch et al. (6) visualized the four-chamber view as well as the origin and double crossing of the aorta and pulmonary trunk in:
• 67% of cases at 11 weeks.
• 80% at 12 weeks.
• 100% at 13–14 weeks.

Outflow tracts – 12-14 weeks of gestation

REFERENCES

1. Braithwaite JM, Armstrong MA, Economides DL. Assessment of fetal anatomy at 12 to 13 weeks of gestation by transabdominal and transvaginal sonography. Br J Obstet Gynaecol 1996;103:82–5

2. Bronshtein M, Siegler E, Eshcoli Z, Zimmer EZ. Transvaginal ultrasound measurements of the fetal heart at 11 to 17 weeks of gestation. Am J Perinat 1992;9:38–42

3. Blaas HG, Eik-Nes SH, Kiserud T, Hellevik LR. Early development of the hindbrain: a longitudinal ultrasound study from 7 to 12 weeks of gestation. Ultrasound Obstet Gynecol 1995;6:240–9

4. Dolkart LA, Reimers FT. Transvaginal fetal echocardiography in early pregnancy: normative data. Am J Obstet Gynecol 1991;165:688–91

5. Johnson P, Sharland G, Maxwell D, Allan L. The role of transvaginal sonography in the early detection of congenital heart disease. Ultrasound Obstet Gynecol 1992;2:248–51

6. Gembruch U, Knopfle G, Bald R, Hansmann M. Early diagnosis of fetal congenital heart disease by transvaginal echocardiography. Ultrasound Obstet Gynecol 1993;3:310–17