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Obstetrics » Obstetrics 1st Trimester
Embryonic demise and spontaneous abortion in progress
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Presentation A young woman with a history of positive pregnancy test presents with vaginal bleeding of one day duration. The pregnancy should be at 12 weeks gestation according to her last menstrual period. An ultrasound done one week prior is shown in images 1-3 . This is followed by sequential transvaginal images and a transabdominal image [images 4-7] from the present scan.
Caption: Sagittal image of the uterus seen one week prior.
Description: An irregularly shaped gestational sac located in the uterine fundus [normal position] is noted. A large subchorionic hemorrhage is seen, which distends the endometrial canal.
Caption: Sagittal scan one week prior.
Description: The subchorionic hemorrhage nearly encircles the gestational sac.
Caption: Sagittal view of the gestational sac seen one week prior.
Description: An echogenic focus is noted within the sac with a CRL of 4 mm [corresponding to 6.1 week gestation]. The sac measures 32 mm, compatible with a gestation of 8 weeks. Cardiac activity was demonstrated. A large amount of hemorrhage surrounds the sac.
Caption: Current transabdominal image of the uterus. Sagittal view.
Description: The uterus is noted again, clearly demonstrating the expulsion of the gestational sac, consistent with a spontaneous abortion in progress.
Caption: Current transvaginal scan performed a week later.
Description: An irregular, elongated gestational sac is now seen in the lower uterine segment. The dimensions of the sac [average diameter 36 mm] are compatible with a greater than 8.5 week gestation. The CRL measures 3 mm [corresponding to 5.4 -6.4 week gestation].
Caption: Current scan showing the fetal heart tracing.
Description: No fetal cardiac motion is identified in this tracing. Because fetal heart motion was present on the previous exam, this is consistent with embryonic demise. (Fetal heart motion may not be detected in normal embryos until they reach 5 mm in size).
Caption: Current sagittal image of the uterus.
Description: Transvaginal scan demonstrating the expulsion of the low lying gestational sac.
Differential Diagnosis Embryonic demise with spontaneous abortion in progress.
Final Diagnosis Embryonic demise with spontaneous abortion in progress. Histopathology of the aborted material revealed immature placental tissue and decidua.
Discussion When a pregnant patient presents with vaginal bleeding in the first trimester, the two conditions that need to be ruled out immediately are ectopic pregnancy and abortion. Threatened abortion is common and occurs in about 25% of clinically apparent pregnancies. Half of the women presenting with threatened abortion ultimately abort, in which cases the embryo is most often already dead. All non-viable gestations eventually abort spontaneously; however, the process of expulsion may be delayed for weeks. The clinical outcome of the process of abortion depends on the status of the cervical os and fetal viability. In such a scenario, determination of fetal viability becomes necessary. Although, clinical history and serial serum B-HCG measurements can provide an insight into the diagnosis, it is recommended that first trimester ultrasound be performed for the assessment of fetal viability in cases of threatened abortion. In addition to signs of fetal life on sonography, subchorionic bleeding is an important factor affecting the outcome of gestations in patients with clinical threatened abortion [Goldstein, et al].

The most common cause for first trimester spontaneous abortion is fetal chromosomal abnormalities. According to McGahan, et al  the sonographic diagnosis of early pregnancy failure depends on the stage of development:
1.Stage A- loss at 3-4 weeks of menstrual age, is usually subclinical loss; no sonographic evidence [these are the women who bleed at the time of their period and often never know they are pregnant].
2.Stage B- loss at 5-6 weeks of menstrual age, sonographic signs based on gestational sac findings.
3.Stage C – loss at 7-8 weeks of menstrual age, sonographic signs of embryonic demise based on demonstration of an abnormal embryo or gestational sac.
4.Stage D – loss at 9-12 weeks of menstrual age, sonographic signs of embryonic demise based on demonstration of abnormal embryo. Structural abnormalities of head, heart, etc may be seen.
So, depending on the menstrual age at presentation, the respective sonographic abnormalities may be looked for.

Ultrasound findings:
• Embryonic cardiac activity – demonstration of cardiac motion indicates that the fetus is alive. Failure to visualize cardiac activity must be interpreted with caution. Cardiac activity is present in normal embryos before it can be detected on ultrasound. Studies by Goldstein and Levi, et al have shown that in normal embryos with CRL of 3 mm or less no cardiac activity may be visualized on ultrasound and follow up is suggested. When the CRL reaches 5 mm or more fetal heart motion should be identifiable.

•Abnormal gestational sac features –
-A large diameter of the sac [dimensions vary depending on whether transabdominal or endovaginal scan is performed], without a demonstratable embryo or yolk sac [i.e. sac size suggests that fetus is of gestational age where embryo and yolk sac should be visualized].
-Irregular or distorted shape.
-Low position of the sac in the endometrial canal.
-Thin decidual reaction [< 2 mm].
-Absent double-decidual reaction.

•Other criteria –
?Collapsing, irregularly marginated amnion,
?Presence of amnion in the absence of a visible embryo.
?Yolk sac calcification.

In conclusion, when evaluating an early pregnancy with ultrasound, the gestational age predicted by the sac size must be correlated with that predicted by the crown rump to exclude a discrepancy. In cases with any question, serial B-HCG measurements and follow up sonography are performed to assess for interval growth.

Case References 1. Coppola PT, Coppola M. Vaginal bleeding in the first 20 weeks of pregnancy. Emerg Med Clin North Am. 2003 Aug; 21(3):667-77.
2. Goldstein SR. Significance of cardiac activity on endovaginal ultrasound in very early embryos. Obstet Gynecol. 1992 Oct; 80(4):670-2.
3. Goldstein SR, et al. Subchorionic bleeding in threatened abortion: sonographic findings and significance. AJR. 1983 Nov; 141(5):975-8.
4. Callen. Textbook of ultrasonography in obstetrics and gynecology. Third edition. Chapter 6: 75-83.
5. Levi CS, et al. Endovaginal US: demonstration of cardiac activity in embryos of less than 5.0 mm in crown-rump length. Radiology. 1990 Jul; 176(1):71-4.
6. McGahan J, et al. Textbook of Diagnostic Obstetrical Ultrasound. Chapter 1 : 15-20.
7. Nazari A, et al. Relationship of small-for-dates sac size to crown-rump length and spontaneous abortion in patients with a known date of ovulation. Obstet Gynecol. 1991 Sep; 78(3 Pt 1):369-73.
Follow Up Histopathology of the aborted material revealed immature placental tissue and decidua.
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