MULTIPLE PREGNANCY (CONCEPT OF TWINNING).pptx

MULTIPLE PREGNANCY
Multiple Pregnancy is simply a pregnancy with more than one fetus. This occurs when multiple eggs are fertilized during one menstrual cycle or when a fertilized egg divides into two or more.
The phenomenon “multiple pregnancy” can lead to two infants born at the same time – Twins. Similarly, there can be birth of three (triplets), four (quadruplets), or more at the same time.
Multiple births are more common in most countries now because of greater access to fertility therapies, including induction of ovulation that occurs when exogenous gonadotropins are administered to women with ovulatory failure, and to those being treated for infertility by assisted reproductive technologies (ARTs).
TWINNING
Twinning refers to the process that leads to the production of more than one offspring at one birth.
In humans the most frequent type of twinning results in the birth of two babies (twins)at once, although repetition of twinning may lead to triplets, quadruplets, or other multiples of one.
It is the nurturing of two conceptuses at the same time.
It is also known as the process of producing two offspring from the same pregnancy
The rate for monozygotic twins is 3 to 4 per 1,000 while Approximately 90% of twins are dizygotic, and their incidence increases with maternal age (doubling at age 35 years) and with fertility procedures, including ART.
About two-third of twins are dizygotic (fraternal) twins. Their incidence increases with maternal age (7–10 per 1000 births)
The incidence of DZ twinning shows considerable racial variation, being approximately 1 in 500 in Asians, 1 in 125 in whites, and as high as 1 in 20 in some African populations.
Although triplets are rare (about 1 per 7,600 pregnancies), birth of quadruplets, quintuplets, and so forth is rarer. In recent years, multiple births have occurred more frequently in mothers given gonadotropins (fertility drugs) for ovulatory
Twins have a high incidence of morbidity and mortality due to preeclampsia, congenital anomalies, premature delivery, etc.
COJOINED (SIAMESE) TWINS – This condition is seen in monozygotic twins. Monozygotic twins in which the inner cell mass (embryoblast) does not completely split. In this condition, two fetuses are joined to each other by a tissue bridge. Conjoined twins are classified into four types based on the site and extent of fusion
(a) Craniophagus: Fusion of heads
(b) Thoracophagus: Fusion of thorax
(c) Cephalothoracophagus: Fusion of head and thorax
(d) Pygophagus: Fusion of sacral regions
The conjoined twins can be separated only if they have no vital parts in common.

TWIN TRANSFUSION SYNDROME
This syndrome occurs in as many as 30% of monochorionicdiamniotic MZ twins.
There is shunting of arterial blood from one twin through arteriovenous anastomoses into the venous circulation of the other twin.

1. Multiple pregnancy and twinning BY OMOGE OLUWATOSIN EMMANUEL (BMSP22/23/H/0358) COURSE CODE: ANA 807 (DEVELOPMENTAL BIOLOGY) LECTURER: DR S.O.A. ODUKOYA MARCH, 2024

2. outline INTRODUCTION EPIDEMIOLOGY TWINS AND FETAL MEMBRANE MONOZYGOTIC TWINS DIZYGOTIC TWINS CLINICAL ANATOMY REFERENCE

3. introduction MULTIPLE PREGNANCY Multiple Pregnancy is simply a pregnancy with more than one fetus. This occurs when multiple eggs are fertilized during one menstrual cycle or when a fertilized egg divides into two or more. The phenomenon “ multiple pregnancy ” can lead to two infants born at the same time – Twins . Similarly, there can be birth of three (triplets) , four (quadruplets) , or more at the same time . Multiple births are more common in most countries now because of greater access to fertility therapies , including induction of ovulation that occurs when exogenous gonadotropins are administered to women with ovulatory failure, and to those being treated for infertility by assisted reproductive technologies (ARTs).

4. INTRODUCTION TWINNING T winning refers to the process that leads to the production of more than one offspring at one birth. In humans the most frequent type of twinning results in the birth of two babies (twins)at once, although repetition of twinning may lead to triplets, quadruplets, or other multiples of one. It is the nurturing of two conceptuses at the same time. It is also known as the process of producing two offspring from the same pregnancy

5. EPIDEMIOLOGY The rate for monozygotic twins is 3 to 4 per 1,000 while Approximately 90% of twins are dizygotic, and their incidence increases with maternal age (doubling at age 35 years) and with fertility procedures, including ART. About two-third of twins are dizygotic (fraternal) twins. Their incidence increases with maternal age ( 7–10 per 1000 births ) The incidence of DZ twinning shows considerable racial variation, being approximately 1 in 500 in Asians, 1 in 125 in whites, and as high as 1 in 20 in some African populations . Although triplets are rare ( about 1 per 7,600 pregnancies ), birth of quadruplets, quintuplets, and so forth is rarer. In recent years, multiple births have occurred more frequently in mothers given gonadotropins (fertility drugs) for ovulatory

6. TWINS AND FETAL MEMBRANES The arrangement of fetal membranes in twins varies considerably, depending upon the type of twins. There are two types of twins: Monozygotic Twins Dizygotic Twins Triplets Births may be derived from: One zygote which can be identical Two zygotes and consist of identical twins and a singleton Three zygotes and be of the same sex or of different sexes

7. Monozygotic (IDENTICAL) twins Monozygotic or Identical Twins result from the fertilization of one secondary oocyte and develop from one zygote to form two separate embryos. Monozygotic twins are of the same sex , genetically identical , and very similar in physical appearance . The process of twinning for this type of twins usually begins in the blastocyst stage ( approximately at the end of the first week). It results from the division of the embryoblast into two embryonic primordia .

8. Monozygotic (IDENTICAL) twins The MZ Twins can be further classified based on the period (timing) of embryonic blastomeres separation/division. It result from splitting of the zygote at various stages of development. DICHORIONIC – DIAMNIOTIC MONOZYGOTIC TWINS Here, there’s an uncommon early separation of embryonic blastomeres. The embryonic blastomeres divides between 2 – 3 days following fertilization. This early separation is believed to occur at the two cell stage , in which two separate zygotes develop and the blastocysts implant separately, resulting in MZ twins with two amnions, two chorions, and two placentas that may or may not be fused but do not have anastomosis of blood vessels . In this case, it is impossible to determine from the membranes alone whether the twins are MZ or DZ.

9. Monozygotic (IDENTICAL) twins

10. Monozygotic (IDENTICAL) twins

11. MONOCHORIONIC – DIAMNIOTIC MONOZYGOTIC TWINS Here, the embryonic blastomeres divides between 3 – 8 days (during the end of the first week) following fertilization. In this case, two separate zygotes develop and the blastocysts implant separately, resulting in MZ twins with a common placenta and a common chorionic cavity but separate amniotic cavities . This is usually the common process of twinning for MZ twins. Monozygotic (IDENTICAL) twins Moore, 2013

12. Monozygotic (IDENTICAL) twins

13. MONOCHORIONIC – MONOAMNOTIC MONOZYGOTIC TWINS Here, the embryonic blastomeres divides between 8 – 13 days following fertilization. This is a rare case whereby the separation occurs at the bilaminar germ disc stage , just before the appearance of the primitive streak . This method of splitting results in formation of two fetus with a single placenta , a common chorionic and amniotic sac . Although the twins have a common placenta, blood supply is usually well balanced. Monozygotic (IDENTICAL) twins

14. Monozygotic (IDENTICAL) twins

15. DIZYGOTIC (fraternal) TWINS Dizygotic or Fraternal Twins result from the fertilization of two secondary oocyte and develop from two zygote to form two separate embryos which may be of the same sex or different sexes . For the same reason, they are no more alike genetically than brothers or sisters born at different times. The only thing they have in common is that they were in their mother’s uterus at the same time.

16. DIFFERENCES BETWEEN MONOZYGOTIC AND DIZYGOTIC TWINS MONOZYGOTIC TWINS DIZYGOTIC TWINS Form from single zygote Form from two zygotes Incidence is more common Incidence is less common Genetically identical Genetically not identical Twins are of the same sex Twins are of the same sex or of different sex Resemblance is similar Resemblance is just like any other two siblings Mostly diamniotic, monochorionic, with single placenta Mostly have two amnions, two chorions, and two placentas

17. CLINICAL ANATOMY Twins have a high incidence of morbidity and mortality due to preeclampsia, congenital anomalies, premature delivery, etc. COJOINED (SIAMESE) TWINS – This condition is seen in monozygotic twins. Monozygotic twins in which the inner cell mass (embryoblast) does not completely split. In this condition, two fetuses are joined to each other by a tissue bridge. Conjoined twins are classified into four types based on the site and extent of fusion (a) Craniophagus : Fusion of heads (b) Thoracophagus : Fusion of thorax (c) Cephalothoracophagus : Fusion of head and thorax (d) Pygophagus : Fusion of sacral regions The conjoined twins can be separated only if they have no vital parts in common.

18. CLINICAL ANATOMY Cephalothoracophagus (Carlson, 2014) Cojoined Twins (Singh, 2012)

19. CLINICAL ANATOMY

20. TWIN TRANSFUSION SYNDROME This syndrome occurs in as many as 30% of monochorionicdiamniotic MZ twins. There is shunting of arterial blood from one twin through arteriovenous anastomoses into the venous circulation of the other twin . The donor twin is small, pale, and anemic, whereas the recipient twin is large and has polycythemia, an increase above the normal in the number of red blood cells. The placenta shows similar abnormalities. PARASITIC TWINS When one member of conjoint twins remains rudimentary due to diminished blood supply and grows like a parasite from the body of the well-developed co-twin, it is termed parasitic twin . Occasionally the parasitic twin may be completely enclosed within the body of the co-twin. In this condition, the fetus is termed fetus in fetu . CLINICAL ANATOMY

21. CLINICAL ANATOMY

22. REFERENCES Moore, K.L., Persaud, T.V.N. and Torchia, M.G. (2013). The Developing Human: Clinically Oriented Embryology. (9 th Edition). Elsevier Saunders, Canada. Carlson, M.B. (2014). Human Embryology and Human Biology. (5 th Edition). Elsevier Saunders, Philadephia . Singh, V. (2012). Textbook of Clinical Embryology. Elsevier Saunders, India. Britannica, The Editors of Encyclopaedia . "multiple birth". Encyclopedia Britannica, 23 Dec. 2023, https://www.britannica.com/science/multiple-birth. (Accessed 10 March 2024).