THE FETUS PAPYRACEUS
Before we could see into the womb, the lost twins most commonly observed were those who were born with the survivor. Signs of a lost twin can be found on the placenta after delivery, in the form of an additional umbilical cord and perhaps a tiny empty sac. Rarely, there is a fetus papyraceus - that is, the mummified body of the lost twin [1] delivered along with the placenta. Many centuries ago in Italy, the birth of babies accompanied by these strange, distorted mummified figures was regarded with fear and suspicion and were known as fera, for the fetus papyraceous resembled the dead young of wild animals. [2] Even today, the fetus papryaceus doesn't look at all like a human fetus, until it is x-rayed and the tiny skeleton can be seen. [3] The tiny body is sometimes very small and easily missed.
THE BLIGHTED TWIN
The fact that twin pregnancies often result in a singleton birth has been well-known in obstetric circles for a very long time. The little lost twin was first known in medical circles as the "blighted twin" [4] because it was already known that most miscarried fetuses are genetically abnormal [5] and the assumption was that the lost twin has died because of some kind of genetic abnormality incompatible with life. The fact that one of a set of born twins can be "blighted" in this way was reported in 1955 [6] In the next few years the so-called "blighted twin" lost in the womb was made the subject of various other reports, all of them assuming some kind of abnormality in the lost twin. By 1958 the lost twins were at last made visible by x-ray, which was being used to diagnose twin pregnancies at the time. [7]
THE ADVENT OF ULTRASONOGRAPHY
Soon after that ultrasound scanning took over as the preferred method for investigating pregnancies as they progressed. [8] In the late 1950s a team of doctors in Glasgow, Scotland, had been working hard on using ultrasonic scans for medical diagnosis of various abdominal cysts and tumours. In 1957 the first article on the use of ultrasound scans for this purpose was published [9]. From this it was just a short step to using ultrasound scans to measure the size of a baby's head in the womb, in order to check on how it was developing. This extraordinary new tool gave doctors a rather fuzzy but useful window on the womb, and they were able to study pregnancy from beginning to end. The darkness of the womb was dispelled from that time onward, and the previously mysterious world of undiagnosed twinning was brought to light. Technology allowed yet another advance: in 1965 Lennart Nilsson created a book of photographs of living fetuses taken in the womb and published them in his book "A Child Is Born", which is still in print. [10] The unborn baby was become more and more familiar to us, but there were further amazing secrets yet to be revealed.
ABNORMAL OR NOT?
In the 1970s it was considered an "abnormal pregnancy" if one of a pair of twins died in the womb. A study of 14 pregnancies made between 1974 and 1979 and using ultrasonograpy revealed that the commonest situation where one twin dies and the other one lives was a normally developed foetus and a "blighted ovum" (i.e. a fertilised egg which had some kind of chromosomal abnormality and which never developed beyond the earliest stages and so looks like an empty sac.) Various other situations were coming to light, such as a normal fetus with an anencephalic (brainless) twin; a normally developing fetus and fetus papyraceus, and even a triplet set consisting of two fetuses papyraceous and one normally developing foetus. [11] All these situations resulted in the birth of one healthy baby, who seemingly suffered no health problems as a result of being accompanied by a twin for some time in the womb. Once these "abnormal pregnancies" could be diagnosed, there was much concern that the survivor may be at risk. It was the policy for a while to deliver the remaining baby as early as possible. However soon it came clear that there was very little health risk to the survivor and it was recognised as a better policy to simply let the pregnancy proceed to term rather than interrupt it, for babies born prematurely are also at risk.
The blighted ovum was hard to diagnose at first, because there is no definite way of telling whether the empty sac is a blighted ovum that would never develop or a healthy embryo at the very earliest stages. Only by repeated scanning would this become clear. [12] Another factor that made it hard to get the bigger picture on vanishing twin syndrome was that on the whole scans were made after a woman had experienced bleeding or the pregnancy was at risk in some way. [13] One of the commonest signs of a vanished twin is bleeding in early pregnancy. [14]
A NEW TERM FOR THE DEATH OF ONE TWIN IN UTERO
In the last twenty years it has become common parlance to describe the intrauterine death of one twin as "vanishing twin syndrome" [15] and those who do not wish to make it sound like some kind of disease prefer the term "vanishing twin phenomenon". The term "vanishing twins" first made an appearance in scientific literature in the early 1980s. First signs that this was an emerging phenomenon came in 1982, when three doctors (two of whom are identical twin gynaecologists) published an article entitled "The vanishing twin" quoting nine research studies. [16] Another followed shortly after [17] and many dozens of others since then. In April 1986 a new term "disappearing twin" was coined by the translator of an article in Czech [18], but it didn't catch on. 1998 a comprehensive review of the existing literature was published under the title "Vanishing twin" with over 50 references. [19] The term "vanishing twin" to indicate the death of one twin in the womb in the first trimester of pregnancy is now in common usage, but is not yet to be found in medical dictionaries. [20]
HOW COMMON IS VANISHING TWIN SYNDROME?
It has been known for a very long time that more twins are conceived than are born, but no one knew until the 1980s just how many little twins are lost before birth. Once a sufficient number of pregnancies had been monitored to be able to produce some statistics, people began to discuss the vanishing twin rate as related to the general twinning rate. Ultrasound gave doctors the chance to find out how many twins were lost before birth, and the result astonished everyone. By 1986 the rate was put at 21.2% of twin pregnancies resulting in a live singleton birth. [21] In 2001 the vanishing twin rate was stated to be slightly higher, at 25.7% [22] but in 1990 Dr Charles Boklage had carried out some statistical research on the probable number of sole survivors of twin or multiple pregnancies. [23] In this report he came to the conclusion that more than 12% of all natural conceptions are multiple. Of those 76% are lost completely, about 2% are born alive in a twin pair, and about 12% are wombtwin survivors. After more thought and research he came to the breathtaking conclusion that for every twin conception resulting in the live birth of a twin pair there are ten wombtwin survivors. His report was published as a chapter in 1995 in "Multiple Pregnancy, Epidemiology, Gestation and Perinatal outcome." [24]
IVF and PREGNANCY REDUCTION
The advent of assisted reproduction techniques (IVF, GIFT, drugs to stimulate ovulation etc.) in the last ten years has brought with it an epidemic of twins and multiple births. The twinning rate increased by 46% between 1980 and 1995.[25] The increase is mainly in fraternal twinning, because the general practice has been to transfer three embryos in order to ensure a viable pregnancy. This practice has caused concern because twins are multiple births are at risk of complications for both mother and child. It is now recommended that only one, special selected embryo is transferred during IVF [26] and this does cut down the incidence of twinning considerably without reducing the number of successful pregnancies resulting from this procedure. [27] However this epidemic of twinning, however long is lasts, will already have created a large population of wombtwin survivors. It is likely that if you were conceived with the help of any kind of artificial reproduction technique you are a wombtwin survivor.
Where triplets, quads or more have begun to develop after the transfer of multiple embryos, it is now usual practice to recommend that the number of embryos be reduced to a more viable number- ie. twins. That means that these surviving twins are both wombtwin survivors. Usually, the selected embryos are injected with potassium chloride at between 10-12 weeks of gestation. Abnormally developing embryos are selected if here are any. [28] Vanishing twin syndrome applies in IVF as much as in any other pregnancy, and by 12 weeks of pregnancy as many as half of the embryos may have vanished in any case. [29] so it's worth waiting for Nature to take its course. Once the injection is performed the dead embryos can be seen gradually vanishing week by week until they are no longer visible on ultrasound. They have not completely vanished however: they are visible once more at birth when there will probably be one or more empty sacs still attached by an umbilical cord; some visible marks on the placenta or a perhaps a little fetus papyraceus. It has been shown [30] that pregnancy reduction carried out in this way does not seem to create any medical risk to the survivors.
Althea Hayton
References and links
1. Final Diagnosis -- Fetus Papyraceus CME case studies. [link]
2. O'Neill, YV Michele Savonarola and the fera or blighted twin phenomenon. Med Hist. 1974 July; 18(3): 222239. [link]
3. Pharoah P. What vanishing twins may be telling us Research intelligence, Issue No.17, University of Liverpool 2003 [link]
4. Nevermann L, Hartge R, Rehder H, Schumann K, Stolp W.Z Particularly small foetus papyraceus after full pregnancy period (author's transl) Geburtshilfe Perinatol. 1981 Jun;185(3):187-91. [Article in German] [link]
5. Quenby S., Vince G., Farquharson R., Aplin J., Recurrent miscarriage: a defect in nature’s quality control? Human Reproduction, Vol. 17, No. 8, 1959-1963, August 2002 [link]
6. Whitehouse DB. Mono-amniotic twins with one blighted; case report. J Obstet Gynaecol Br Emp. 1955 Aug;62(4):610-1. [link]
7. Melnick RN, Godsick WH Blighted twin diagnosed by x-ray.. New York State Journal of Medicine 1958 May 15;58(10):1743-4. [link]
8.Moore RM Jr, Jeng LL, Kaczmarek RG, Placek PJ. Use of diagnostic ultrasound, X-ray examinations, and electronic fetal monitoring in perinatal medicine. J Perinatol. 1990 Dec;10(4):361-5. [link]
9. Woo, J. A short History of the development of Ultrasound in Obstetrics and Gynecology (website) [link]
10. Nilsson L A Child is Born : The Completely New Editon Dell 1986 [link]
11 Kurjak A, Latin V. Ultrasound diagnosis of fetal abnormalities in multiple pregnancy.Acta Obstet Gynecol Scand. 1979;58(2):153-61. [link]
12 Bernard KG, Cooperberg PL. Sonographic differentiation between blighted ovum and early viable pregnancy. AJR Am J Roentgenol. 1985 Mar;144(3):597-602. [link]
13 Finberg HJ, Birnholz JC Ultrasound observations in multiple gestation with first trimester bleeding: the blighted twin. Radiology. 1979 Jul;132(1):137-42. [link]
14 Saidi,M. H First-Trimester Bleeding and the Vanishing Twin: A Report of Three Cases Journal of Reproductive Medicine Volume 33, Number10/October 1988 On e of a series of artices about vanishing twin phenomenon (website) [link]
15 Anderson-Berry A. Vanishing twin syndrome e-medicine June 4 2004 (website) [link]
16 Landy HJ, Keith L, Keith D. The vanishing twin. Acta Genet Med Gemellol (Roma). 1982;31(3-4):179-94. [link]
17 International Planned Parenthood Federation IPPF. The vanishing twin. Res Reprod. 1983 Oct;15(4):1-2. [link]
18 Maly Z, Burnog T The disappearing twin--a new phenomenon in ultrasonic diagnosis in pregnancy [Article in Czech] Cesk Gynekol. 1986 Apr;51(3):147-9. [link]
19 HJ Landy and LG Keith The vanishing twin: a review Human Reproduction Update, Vol.4, No.2 pp.177-183, 1998 [link]
20 Online medical dictionary (no result for "vanishing twin" ) [link]
21 Landy HJ, Weiner S, Corson SL, Batzer FR, Bolognese The "vanishing twin": ultrasonographic assessment of fetal disappearance in the first trimester. RJAm J Obstet Gynecol. 1986 Jul;155(1):14-9 [link]
22 Malinowski W Intrauterine death of one fetus during the first trimester in multiple gestation [Article in Polish] Ginekol Pol. 2001 Jul;72(7):541-6. [link]
23 Boklage CE Survival probability of human conceptions from fertilization to term. Int J Fertil. 1990 Mar-Apr;35(2):75, 79-80, 81-94. [link]
24 Blickstein I and Keith L.G Multiple Pregnancy - Epidemiology, Gestation & Perinatal Outcome (2nd edition) Taylor & Francis 2005 (review and contents ) [link]
25 Keith L, Klock, S Gandhi, S Iatrogenic Multiple Pregnancy Epidemiology, Risks, and Ethical Dilemmas Obgyn.net [link]
26 De Neubourg D, Gerris J, Van Royen E, Mangelschots K, Valkenburg M. Prevention of twin pregnancy after IVF/ICSI using embryo transfer [Article in Dutch] Verh K Acad Geneeskd Belg. 2002;64(5):361-70 [link]
27 A. Tiitinen, L. Unkila-Kallio, M. Halttunen and C. Hyden-Granskog Impact of elective single embryo transfer on the twin pregnancy rate Human Reproduction, Vol. 18, No. 7, 1449-1453, July 2003 [link]
28 Lt Col SK Rath, Surg Capt Sushil Kumar, Lt Col RK Sharma, Maj PS Rao Multifetal Pregnancy Reduction Medical Journal Armed Forces India.Vol. 60 No. 1 January 2004 [link]
29 Blumenfeld Z, Dirnfeld M, Abramovici H, Amit A, Bronshtein M, Brandes JM.Br J Obstet Gynaecol. 1992 Apr;99(4):333-7. Spontaneous fetal reduction in multiple gestations assessed by transvaginal ultrasound. [link]
30 Antsaklis A.J, Drakakis P. , Vlazakis V. and Michalas S. Reduction of multifetal pregnancies to twins does not increase obstetric or perinatal risks Human Reproduction, Vol. 14, No. 5, 1338-1340, May 1999 [link]
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