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Yolk Sac Diameter in Multiple Gestations

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Case Studies Yolk Sac Diameter in Multiple Gestations Chelsea Fox, MD; Karenne Fru, MD, PhD; and Bruce A. Lessey, MD, PhD From the Department of OB/GYN, Greenville Health System, Greenville, SC (C.F., B.A.L.), University of South Carolina School of Medicine Greenville, Greenville, SC (B.A.L.), and Department of Obstet- rics and Gynecology, New Hanover Regional Medical Center, Wilmington, NC (K.F.) Abstract Enlargement of the yolk sacs is an ominous sign even in multi-gestational pregnancies. he yolk sac functions as the primary route ity conceived after placement of 2 embryos on of exchange between the embryo and post-retrieval day 3. Quantitative hCG levels were Tmother prior to the establishment of the higher than expected and transvaginal ultrasound placental circulation. It is well established that an at 6 weeks’ gestation demonstrated a triplet preg- abnormally large yolk sac serves as a prognostic nancy with a singleton sac and a separate mono- indicator for early pregnancy failure in singleton chorionic-monoamniotic versus conjoined twin gestation. However, no studies have been per- pregnancy with symmetrically enlarged yolk sacs, formed to describe normal versus abnormal yolk each with cardiac activity present (Figs. 1A and B). sac diameters (YSD) in multiple gestations. In this The yolk sacs associated with the twin pregnancy case, we describe a patient with triplet pregnancy were 6.15 mm and 7.37 mm, respectively, while the consisting of monochorionic-monoamniotic singleton had a normal yolk sac. A repeat ultra- twins both with enlarged yolk sacs in addition to sound 10 days later confirmed absence of fetal car- singleton pregnancy in a separate sac with a nor- diac activity in the monochorionic-monoamni- mal yolk sac. The monochorionic-monoamniotic otic sac, with increased crown rump length of the twins were later diagnosed with a fetal demise singleton pregnancy, which maintained persistent suggesting large YSD may serve as a poor prog- cardiac activity. This embryo went on to normal nostic indicator in multiple gestations as well. development and delivery. A second example of a twin pregnancy with normal yolk sacs is shown in Case Description Figure 1C. In this example, these twins went on to A 34-year-old woman opting for in vitro fertil- sustain normal development and were delivered ization (IVF) as treatment for primary infertil- successfully. Figure 1 (A and B) Yolk sac size in a multi-gestational pregnancy predicted an adverse outcome of the affected mono- mono twins of a triplet pregnancy. (C) Another twin pregnancy with dichorionic-diamniotic embryos with reassuring normal appearing yolk sacs continued and developed normally. GHS Proc. May 2016; 1 (1): 47-48 47 Correspondence Discussion While it is widely accepted that monoamniotic twins share a yolk sac, recent evidence shows Address to: The routine use of ultrasound is a key feature in the monoamniotic twins with 2 yolk sacs.4,5 This case Chelsea Fox, MD modern management of early pregnancy. In par- Greenville Health also challenges the previously held idea that the ticular, the yolk sac has been studied as a prognos- System, Dept of number of yolk sacs is equal to amnionicity in tic indicator for pregnancies. The secondary yolk OB/GYN sac is the primary source of exchange between the both monochorionic-monoamniotic and mono- 890 W Faris Rd 4 embryo and the mother during organogenesis.1 It chorionic-diamniotic twin pregnancies. While Greenville, SC 29605 the question of amnionicity may require further ([email protected]) is first visualized at 5 weeks’ gestation, or when the gestational sac reaches 10 mm2, and regresses by study, this case bears out the fact that abnormally the 12th week of gestation in normal pregnancies.2,3 large yolk sacs are predictive of abnormal preg- A normal range of yolk sac diameters has been nancy even in multiple gestations. Moreover, only described, particularly in singleton pregnancies the affected sacs with enlarged yolk sacs suffered with abnormal outcome in all cases where YSD the expected adverse sequelae. The singleton preg- was greater than 5.6 mm.1 Lindsay et al followed nancy was carried to term with no further evi- 486 first-trimester pregnancies and found a YSD dence of the twin pregnancy following embryonic >2SDs (standard deviations) above the mean was demise. This is, to the best of our knowledge, the associated with abnormal outcomes with a sensi- first case report demonstrating that enlarged yolk tivity of 15.6%, specificity of 97.4%, and a positive sacs in twins may be associated with adverse out- predictive value of 60.0%.1 There is a paucity of comes similar to singleton pregnancies; the case data for normal versus abnormal YSD in multiple also adds to the growing body of literature sug- gestations. However, there is no reason to suspect gesting yolk sac number does not always correlate that similar guidelines regarding enlarged yolk with amnionicity in first-trimester monochori- sacs and poor prognosis would not apply. onic multiple gestations.6-10 References 1. Lindsay DJ, Lovett IS, Lyons EA, Levi CS, Zheng XH, H, Torii Y. Monochorionic monoamniotic twin preg- Holt SC, Dashefsky SM. Yolk sac diameter and shape nancies with two yolk sacs may not be a rare finding: at endovaginal US: predictors of pregnancy outcome a report of two cases. Ultrasound Obstet Gynecol. in the first trimester. Radiology. 1992;183:115-8. 2010;36:384-6. 2. Jauniaux E, Jurkovic D, Henriet Y, Rodesch F, Hustin 7. Malinowski W. Yolk sacs in twin pregnancy. Acta J. Development of the secondary human yolk sac: cor- Genet Med Gemellol (Roma). 1998;47:177-81. Hum relation of sonographic and anatomic features. 8. Shen O, Samueloff A, Beller U, Rabinowitz R. Num- Reprod . 1991;6:1160-6. ber of yolk sacs does not predict amnionicity in early 3. Berdahl DM, Blaine J, Van Voorhis B, Dokras A. first-trimester monochorionic multiple gestations. Detection of an enlarged yolk sac on early ultrasound Ultrasound Obstet Gynecol. 2006;27:53-5. Fertil if associated with adverse pregnancy outcomes. 9. Corbett S, Shmorgun D. Yolk sac number does not Steril . 2010;94:1535-7. predict reliably amnionicity in monochorionic twin 4. Levi CS, Lyons EA, Dashefsky SM, Lindsay DJ, Holt pregnancies: a case of monochorionic monoamniotic SC. Yolk sac number, size and morphologic features in twin pregnancy with two distinct yolk sacs on early monochorionic monoamniotic twin pregnancy. Can first-trimester ultrasound. Ultrasound Obstet Gyne- Assoc Radiol J. 1996;47:98-100. col. 2012;39:607-8. 5. Bishop DK. Yolk-sac number in monoamniotic twins. 10. Meller C, Wojakowski A, Izbisky G, Aiello H, Otaño Obstet Gynecol. 2010;116:504-7. L. Number of yolk sacs in the diagnosis of monoamni- 6. Murakoshi T, Ishii K, Matsushita M, Shinno T, Naruse onicity. J Ultrasound Med. 2014;33:1091-7. 48 GHS Proc. May 2016; 1 (1): 47-48.
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