1. Benirschke K, Kim CK. Multiple pregnancy. N Engl J Med 1973; 288(25): 1329-1336.
2. Sabbagha R. Diagnosis and fetal congenitive anomalies by ultrasonography. In Keith L, Papiernik E, Keith D, Luke B, eds. Multiple Pregnancy. Athens: Parthenon Publishing, 1995; 239-268.
3. Rodis JF, Egan JF Craffey A, Ciarleglio L, Greenstein RM, Scorza WE. Calculated risk of chromosomal abnormalities in twin gestations. Obstet Gynecol 1990; 76(6): 1037-1041.
4. Benirschke K. Multiple gestation: incidence, etiology and inheritance. In: Creasy RK, Resnik R (eds). Maternal-Fetal Medicine Principles and Practice, 4th Edition. Philadelphia: WB Saunders Co, 1999; 585-615.
5. Weinblatt V, Wapner RJ. Chorionic villus sampling and amniocentesis in multiple pregnancy. In: Monteagudo A, Timor Tritsch I, eds. Ultrasound and Multiple Pregnancy. Athens: Parthenon Publishing, 1998; 201-211.
6. Gardner S, Burton BK, Johnson AM. Maternal serum alpha-fetoprotein screening: a report of the Forsyth County project. Am J Obstet Gynecol 1981; 140(3): 250-253.
7. Pergament E. Prenatal genetic diagnosis: amniocentesis and chorionic villus sampling. In: Keith L, Papiernik E, Keith D, Luke B, eds. Multiple Pregnancy. Athens: Parthenon Publishing, 1995; 313-324.
8. Sebire NJ, Snijders RJ, Hughes K, Sepulveda W, Nicolaides KH. Screening for trisomy 21 in twin pregnancies by maternal age and fetal nuchal translucency thickness at 10-14 weeks of gestation. Br J Obstet Gynaecol 1996; 103(10): 999-1003.
9. Okaro E, Gagnon A, Vandenberg K, Ville Y. Aspects of perinatal diagnosis in twin pregnancies. Gynaecol Forum 1998; 3: 19-26.
10. Pandya PP, Snijders RJ, Johnson SP, De Lourdes Brizot M, Nicolaides KH. Screening for fetal trisomies by maternal age and fetal translucency thickness at 10 to 14 weeks of gestation. Br J Obstet Gynaecol 1995; 102(12): 957-962.
11. Al-Kouatly H, Skupski D. Twin pregnancy. Curr Opin Obstet Gynecol 1999;11(2):125-129.
12. O’ Brien JE, Dvorin E, Yaron Y, Ayoub M, Johnson MP, Hume RF Jr, Evans MI. Differential increases in AFP, hCG, uE3 in twin pregnancies impact on attempts to quantify Down syndrome screening calculation. Am J Med Genet 1997; 73:109-112.
13. Nicolini U, Monni G. Intestinal obstruction in babies exposed in utero to methylene blue. The Lancet 1990; 36: 1258-9.
14. Kidd SA, Lancaster PA, Anderson JC, Boogert A, Fisher C, Robertson E, Wais DM. Fetal death after exposure to methylene blue dye during mid-trimester amniocentesis in twin pregnancy. Prenat Diagn 1996; 6: 39-47.
15. Jeanty P, Shah D, Roussis P. Single needle insertion in twin amniocentesis. J Ultrasound Med 1990; 9(9): 511-517.
16. Megory E, Weiner E, Shalev E, Ohel G. Pseudoamniotic twins with cord entanglement following genetic funipuncture. Obstet Gynecol 1991; 78(5 Pt 2): 915-917.
17. Pruggmayer MR, Jahoda MG, van der Pol JG, Baumann P, Holzgreve W, Karkut G, Lettau R, Eiben B, Osmers R, gola HW, Duda V, Polak P, Korner H, Schulte-Valentin M, Schutte H. Genetic amniocentesis in twin pregnancies: results of a multricenter study of 529 cases. Ultrasound Obstet Gynecol 1992; 2(1): 6-10.
18. Ghidini A, Lynch L, Hicks C, Alvarez M, Lockwood CJ. The risk of second trimester amniocentesis in twin gestation; a case control study. Am J Obstet Gynecol 1993; 169(4): 1013-1016.
19. Pergament E, Schulman JD, Copeland K, Fine B, Black SH, Ginsberg NA, Frederiksen MC, Carpenter RJ. The risk of and efficacy of chorionic villus sampling in multiple gestations. Prenat Diagn 1992; 12(5): 377-384.
20. Wapner RJ, Johnson A, Davis G. Prenatal diagnosis in twin gestation: a comparison between second trimester amniocentesis and first trimester chorionic villus sampling. Obstet Gynecol 1993; 82: 49-56.
21. van der Berg C, Braat AP, van Opstal D, Halley KJ, Kleijer WJ, den Hollander NS. Amniocentesis or chorionic villus sampling in multiple gestation? Experience with 500 cases. Prenat Diagn 1999; 191: 234-244.
22. Antsaklis A, Gougoulakis A, Mesogitis S, Papantoniou N, Avarantinos D. Invasive techniques for fetal diagnosis in multiple pregnancy. Int J Gynecol Obstet 1991; 34(4): 309-314.