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Twinning and Multiple Pregnancy: Complications, Types and Mechanisms
- 1. TWINNING AND MULTIPLE PREGNANCY FACILITATOR- PROF. NGASSAPA PRESENTERS MUHUMUZA NEVILLE TUSAL MAVJI PATEL EVANS .A. MLAY PATRICE KUETE MEKONTCHOU YONAZ MBONEA REUBEN ALEX ELIUS
- 2. OBJECTIVES Upon completion of this session, students are expected to be able to: • Define twinning and multiple pregnancy • Describe the epidemiology of twin pregnancy • Describe the types of twin pregnancy • Explain the mechanism of twinning • Identify complications of multiple pregnancy
- 3. OUTLINE 1. DEFINITION 2. EPIDEMIOLOGY 3. TYPES OF TWINS 4. MECHANISM OF TWINNING 5. COMPLICATIONS 6. REFERENCES
- 4. DEFINITION Multiple pregnancy - A pregnancy in which more than one fetus develops in the uterus simultaneously. • Two fetuses (twins) • Three fetuses (triplets) • Four fetuses (quadruplets) • Five fetuses (quintuplets) • Six fetuses (sextuplets)
- 5. EPIDEMIOLOGY. • The incidence of multiple births increased significantly in late 20th century. • The increasing is due to the use of ART (Assisted Reproductive Therapy) and advanced maternal age at time of conception. Types of twins Global prevalence Tz Prevalence Monozygotic twins 2-4:1000 births Dizygotic ~7-10:1000 births Triplets 1:7000-10000 births Quadruplets 1:600,000 births
- 7. TYPES OF TWINS Dizygotic twins • Are also called Fraternal, two-egg or binovular twins • Make up 2 3 of all twin pregnancies Monozygotic twins • Syn. identical or uniovular twins • Make up 1 3 of all twin pregnancies.
- 9. • Make up two-thirds of all twin pregnancies. • result from fertilization of two ova, usually of the same or one from each ovary, by two different sperms during a single ovarian cycle. • The resultant two zygotes form two blastocysts—each of which implants separately into the uterine endometrium. MECHANISM OF TWINNING Dizygotic twins (fraternal):
- 10. • These twins are not genetically alike. Hence have no more resemblance than any other two brothers and sisters. • They may or may not be of different sex. • They are di-amniotic and di-chorionic
- 11. DIAGRAMATIC PRESENTATION OF DIZYGOTIC TWIN FORMATION
- 12. Monozygotic twins (identical): • One third of all twins • Result from cleavage of a single fertilized ova • The timing of cleavage determines placentation. – Always of same sex – Identical including the HLA genes(isografting) – However fingerprints may differ.
- 14. Dichorionic/diamniotic monozygotic twins: • Cleavage within 0-4 days after fertilization • Division prior to morula stage (2 cell stage) • Each fetus will be surrounded by amnion & chorion like dizygotic twins • Has the lowest mortality rate of monozygotic twins.
- 15. Monochorionic/diamniotic • Cleavage between day 4 and 8 after fertilization • Splitting of the zygote usually occurs at the early blastocyst stage. • The inner cell mass splits into two separate groups of cells within the same blastocyst cavity • Division after differentiation of the trophoblast but before the amnion formation. • Share single placenta but separate amniotic sac (monochorionic diamniotic) • The mortality rate is 25%
- 16. Monochorionic/monoamniotic • < 1% of cases • Cleavage after the 8th day (day 9-12) • Division after amnion differentiation • Share single placenta & single sac • High risk of twin to twin transfusion • Mortality is 50-60%, usually before 32 weeks
- 17. Image showing mechanism of monozygotic twinning
- 20. Superfecundation: • Is an extremely rare phenomenon that occurs when a second ova released during the same menstrual cycle is additionally fertilized by the sperm cells of a different man in separate sexual intercourse.
- 21. Superfetation: • Superfetation can be defined as the ovulation, fertilisation and implantation of a second or additional embryo(s) during pregnancy.
- 22. Heterotopic pregnancy • presence of multiple gestations, with one being present in the uterine cavity and the other outside the uterus, commonly in the fallopian tube and uncommonly in the cervix or ovary.
- 24. COMPLICATIONS OF MULTIPLE PREGNANCY The complications can be divided into • Fetal complications • Maternal complications
- 25. FETAL COMPLICATIONS (Congenital malformation) Congenital malformations occur as twice in twins compared to singleton pregnancy. One percent of monozygotic twins have malformations These may include;- a) Conjoined twins b) Parasitic twins c) Acardiac twins
- 26. a) Conjoined (Siamese) twins Originate from incomplete division of the unizygote. If the division occurred after embryonic disc formation, incomplete or conjoined twins will occur. Separation take place after 13th day.
- 27. They are classified according to the nature and degree of union.(pagos, fasterned) – Omphalopagus – Thoracopagus-joined at the thorax – Craniopagus(twins joins at the head) – Pyopagus(twins joins at sacral region)
- 28. • The type of twins formed depend upon when and to what extent abnormalities of the node and streak occured. • Some conjoined twins are separable surgically, if no common internal organs which may lead to death.
- 29. Illustration of various types of Siamese twins
- 30. Sanchia and Eman Mowatt
- 31. Twin to twin transfusion • Vascular communication between two fetuses, mainly in mono chorionic placenta • Account 10% of monozygotic twins • Twins are often of different sizes • One is a donor and another is recipient • Donor twin is small,dehydrated, oligohydraminous and anemic , usually dies due to anemic heart failure • Recipent twin = edematos ascites enlarged liver polyhydramnious from congestive heart failure
- 33. PARASITIC TWIN • One member of the pair may be rudimentary due to diminished blood supply and grow like a parasite on the body of a well develop twin. • May be full or partial complement of organs. • The condition is known as fetus in fetu.
- 35. TRAP • This refers to Twin Reversed Arterial Perfusion Syndrome Or Acardiac Twin. • Absent heart in one fetus with arterial arterial communication in placenta, donor twin also dies. • Twin has no head, upper limbs and upper trunk. while the lower part of the trunk and lower limbs are well formed • Such a twin is known as acardiac acephalic twin • Amorphous twin-shapeless mass of bones, skin etc
- 36. • The normal fetus – “Pump Twin” • Rabnormal fetus – TRAP twin
- 37. Blighted Twin/ Vanishing Twin Syndrome • Is a condition in which one of a set of twins or multiple embryos dies in utero, disappear, or gets resorbed partially or entirely, with an outcome of a spontaneous reduction of a multi-fetus pregnancy to a singleton pregnancy, portraying the image of a vanishing twin. • This phenomenon can range from the disappearance of an early empty gestational sac to a sac that had developed a fetal pole to a fetus with documented heart activity.
- 39. Maternal Complications • Increased pregnancy risks such as;- • Anaemia(15%); due to iron deficiency or folic acid deficiency • Pre eclampsia • Threatened or actual abortion • Polyhydramnios- more common in monozygotic • Ante Partum Hemorrhage(APH) • Psychological problems • Mechanical risks; supine hypotension syndrome, Increased varicosities, pressure on the ureter with increased urinary tract infections
- 40. Increased labour risks • Pre term labour (50%) twins -37 weeks, triplets-34 weeks, quadruplets -30 weeks. • Abnormal fetal presentations • Locked twins or entanglement • Cord prolapse • Post Partum Haemorrhage • Puerperal sepsis
- 41. References • Williams Obstetrics 24th Edition by Cunningham, Leveno et al • Essential of human embryology by Kaduri and Ngassapa. • Textbook of Clinical Embryology by Vishram Singh • https://www.bbc.com/news/uk-england-birmingham- 54841555 • UpToDate
- 42. MAY ONE OF YOU BE BLESSED WITH SUCH A BEAUTIFUL BUNDLE
Editor's Notes
- Each fetus will be surronded by amnion & chorion( each fetus has its own placenta) Product of Fertilization of 2 ova by 2 sperms It is inherited as recessive autosomal trait via female descendants, Martenal height and weight Increased martenal age,35-45years White mothers of blood group A and O Race has special importance: Blacks(Nigeria 49/1000>whites(U.S.A 12/1000)>asians(Japan1.3/1000)
- Identical including the HLA genes(isografting) mirror images of one another), however fingerprints differ. Not genetically determined, Constant rate in all races 2.3-4/1000 pregnancies.
- Mechanism of monozygotic twinning. Black boxing and blue arrows in columns A, B, and C indicate timing of division. A. At 0 to 4 days postfertilization, an early conceptus may divide into two. Division at this early stage creates two chorions and two amnions (dichorionic, diamnionic). Placentas may be separate or fused. B. Division between 4 and 8 days leads to formation of a blastocyst with two separate embryoblasts (inner cell masses). Each embryoblast will form its own amnion within a shared chorion (monochorionic, diamnionic). C. Between 8 and 12 days, the amnion and amnionic cavity form above the germinal disc. Embryonic division leads to two embryos with a shared amnion and shared chorion (monochorionic, monoamnionic). D. Differing theories explain conjoined twin development. One describes an incomplete splitting of one embryo into two. The other describes fusion of a portion of one embryo from a monozygotic pair onto the other.
- In December 2001, a perilous operation took place in Birmingham to separate three-month-old conjoined twins, Sanchia and Eman Mowatt. They started life in the full focus of the world's media, such was the rarity of their predicament. What are the 19-year-old sisters who defied the medical odds doing today? https://www.bbc.com/news/uk-england-birmingham-54841555
- Twin reversed arterial perfusion (TRAP) sequence or acardiac twinning is a very rare problem, occurring in approximately 1% of monochorionic twins (MC, twins sharing one placenta). One twin is usually structurally completely normal. The other is an abnormal mass of tissue, consisting usually of legs and a lower body, but no upper body, head or heart. Because of the absent heart, the term “acardiac twin” has been used to describe this mass. The normal fetus is referred to as the “pump twin” because its heart is used to pump blood to the abnormal mass. The “acardiac twin” has no chance of survival. Due to the absence of a beating heart, the acardiac does not send blood to any portion of the placenta, and all of its blood supply comes from and goes back to the circulation of the pump twin through unique vascular connections on the surface of the shared placenta. Arteries usually carry blood away from the fetus and toward the placenta to receive oxygen from the mother’s circulation. When there is an “acardiac twin”, the unique vascular connections allow blood in the artery to flow in the reversed direction (toward the acardiac fetus rather than away from it). Thus, the phrase “twin reversed arterial perfusion” (TRAP) sequence has been used to describe this condition. The normal “pump” twin faces the excess burden of having to send and receive blood to the acardiac mass as well as to its own growing tissues. As such, the normal twin’s heart has to work extra hard and is under a lot of stress. This can result in heart failure for the normal twin. Left untreated, up to 50% of these otherwise normal twins may die in utero (stillbirth) or die shortly after birth.