What is your Diagnosis: Fetus at 12 Weeks Gestation

June 14, 2012

This is the case of a pregnancy at 12 weeks gestational age. The patient underwent routine prenatal transabdominal and transvaginal ultrasound imaging.

History and Symptoms: This patient came in for routine ultrasound examination at 12 weeks gestational age. She had normal menstrual cycles before the pregnancy and did not have a history of any major illness. This was her second pregnancy.

Family History: The patient (the mother) was one of 2 children.

Present Pregnancy: The patient had a history of 12 weeks amenorrhea which corresponded with the age of the fetus on the ultrasound scan. She had a history of mild spotting during the 1st week of her pregnancy.

Clinical Examination: Her blood pressure was normal (BP: 122/ 84 mm. of Hg) and her other vital signs were normal. On abdominal examination, there were no major clincal findings.  The fundal height of the patient corresponded to the age of the fetus at 12 weeks.

Imaging Studies: This patient underwent routine transabdominal and transvaginal ultrasound imaging to study the biophysical profile of the fetus and to rule out any anomalies.


Image 1: Transabdominal sagittal section of fetus
(Images courtesy of Dr. Jaydeep Gandhi, India).


Image 2: Transabdominal Sagittal section of fetus:

What are your findings based on these 2 images?

Sonographic Findings: Let's analyze the images of the fetus. They are obviously not normal. The most striking finding that we see is a hypoechoic collection deep in the skin on the posterior aspect of the neck and thorax of the fetus. What kind of fetal disease would produce these appearances? What are the diagnostic possibilities for such a fetal condition?

The first possibility is a normal amniotic membrane around the fetus. Indeed the amniotic membrane can often mimic nuchal translucency. To clearly identify the nature of this lesion, view the transvaginal image 3.


Image 3: Transvaginal ultrasound image of the fetus: transverse section fetal chest and abdomen

In image 3, the amniotic membrane is clearly identified separately from the fetus.

What finding is most striking now?

What are the chief diagnostic possibilities in this case?

Perhaps the most striking finding in this fetus is the presence of a thickening of the skin around the fetus, and from the above images the condition primarily affects the fetal chest, abdomen and neck. This leads us to the conclusion that the lesion we are observing is indeed a skin lesion.

Is this an increase in nuchal translucency thickness? Obviously there is a hypoechoic collection posterior to the neck of the fetus and within the subcutaneous plane. Do we have a diagnosis? Observe image 4 and 5.


Image 4: Transvaginal image in sagittal section: trunk and fetal head


Image 5: Transvaginal image of the fetus: coronal plane

What are the various conditions that can produce the appearances we see in this fetus?

The common diseases that can cause a diffuse thickening, in this case edema of the skin of the fetus are increased nuchal translucency thickness, cystic hygroma, fetal anasarca and fetal hydrops (hydrops fetalis).  How do we distinguish these various entities and find a suitable diagnosis in this fetus?

Discussion: The first possibility of an increased nuchal translucency can be ruled out because the cutaneous edema involves most of the fetal body from the head down to the chest and abdomen. In addition, image 3 shows that there is webbing of the edematous skin around the posterior aspect of the neck. This is more suggestive of cystic hygroma.

However cystic hygroma would not involve the rest of the body of the fetus. In this case, the only remaining possibility is that of hydrops fetalis, although in an early stage. However, fetal hydrops is characterized by global fetal cutaneous edema with fluid in at least one body cavity. Do we see that here?

A careful study of the images shows that there is a very thin, subtle anechoic collection within the fetal chest and abdomen. This is the evidence we need to clinch the diagnosis of hydrops fetalis. The diagnosis of fetal hydrops in such an early stage of pregnancy, (12 weeks) is made with considerable caution as fetal imaging techniques keep increasing in resolution.

Hydrops fetalis is an end-stage condition for a wide variety of diseases. It is said to be the abnormal accumulation of interstitial fluid in at least two body cavities (pleural, peritoneal, or pericardial) or one body cavity in association with anasarca (generalized massive edema). Hydrops fetalis can be either immune or non immune in nature. Immune hydrops is characterized by a circulating antibody against red blood cells (RBCs) in the mother, whereas in nonimmune hydrops, no such antibody is found. Before the rigorous use of Rh anti-D immune globulin, immune hydrops was rampant. However, today, most cases of hydrops are non-immune in etiology.

Final Diagnosis: Early fetal hydrops (hydrops fetalis)

Prognosis: The incidence of non-immune hydrops is one in 1500 pregnancies. The prognosis of non-immune hydrops, once diagnosed, is very poor, with a mortality rate of as high as 70 %. With recent advances in in-utero therapy substantial gains have been made in the management of hydrops fetalis. However, such therapies are not widely available and hence its scope is limited to advanced institutes.

References:

References
1) Callen, PW.Non-Immnue Hydrops Fetalis Parvovirus B19. OB-GYN Ultrasound Online
2) Rumack, C. Diagnostic Ultrasound, 4th edition
3) Sabih, D., Lin EC., Eugene C Lin, MD, et al.Hydrops Fetalis. Medscape, Updated May 25, 2011
4) Ultrasound-images.com.