This is a 27 year-old patient with an otherwise unremarkable pregnancy.

The following images were obtained during an ultrasound examination performed at 20 weeks of gestation.

Fetal head is normal.

In this image we can clearly see the head to abdomen disproportion.

Fetal thorax show an enlarged heart (cardiothoracic ratio 50%).

No stomach was visible in any of the ultrasound examinations performed to this patient.

Single umbilical artery was demonstrated with color Doppler.

The fetal biometry parameters show a 3-week discordance between abdomen and skeletal measurments. There was also a 2-week discordance between abdominal and head perimeters.

• Biparietal diameter :                 42.9 mm 18w1d
• Head perimeter:                        169 mm 19w3d
• Abdominal perimeter:                125 mm 17w6d
• Humerus:                                    30.3 mm 20w0d
• Femur:                                           33 mm 20w3d

X-ray rendering of the fetal spine. The coronal view clearly show that this baby had no scoliosis.

Same rendering of sagittal view of the fetal spine showing thoracic kyphosis.

The fetal over-flexed position is seen in this next picture.

In view of all these findings, an amniocentesis was performed. The FISH study (Fluorescent in-situ hybridization) returned normal. We had suspected a chromosomal anomaly in view of the multiplicity and the multi-system anomalies.

The conventional cytogenetic study, showed the following:

46, XX, r (14) (p11.2q32) [13]/ 45, XX, - 14 [7]

What does this mean?

In conventional cytogenetics, the geneticist usually analyses 20 metaphases. In this case, out of the 20 analyzed cells, 13 featured a female karyotype (46, XX), with a ring chromosome derived from chromosome 14 [r (14)] . The remaining seven metaphases showed monosomy 14 (45, XX, -14). The ring chromosome is formed by the breakage of p-ter (chromosome 14 short arm terminal portion), which is p11.2, and the q-ter (chromosome 14 long arm terminal portion) which is q32. This means that the chromosome breaks on both sides of the chromosome 14 centromere and these ends then fuse, giving rise to this "ring chromosome".

These following two images show both genetical conditions:

First the ring chromosome 14 (highlighted in red)

The other cellular line encountered with the missing chromosome 14 (monosomy 14).

Why did this happen?

This particular ring chromosome 14 may be sporadic (de novo), or transmitted by a carrier parent (usually from the mother). In order to determine its origin, and also to estimate the reproductive risk of the parents, parental karyotyping is strongly advised.

So, the final diagnosis for this case is a mosaic  Chromosome 14 ring with monosomy 14