Multiple pregnancies

1. Multiple pregnancies

2. Definition Pregnancies resulting in the birth of more than one neonate at a time are graded as multiple pregnancies.

3. Types of multiple pregnancies • Multiple pregnancies may be • mono-ovular (identical) or • poly-ovular (fraternal)

4. Mono-ovular multiple pregnancies result from fertilization of a single ovum that will later on split into two. • They are also called mono-zygotic type of multiple pregnancies.

5. The embryos, fetuses and neonates resulting from a mono-zygotic pregnancy are called mono-zygotic (Identical) twins. • In other words twins resulting from one zygote are mono-zygotic twins.

6. These twins will share 100% same DNA, • They have the same hand and footprints and • Yet have different teeth marks and fingerprints.

7. Poly-ovular multiple pregnancies result from fertilization of more than one secondary oocyte. • They are usually di-zygotic type of multiple pregnancies. • But it may be tri-zygotic type, tetra-zygotic and so on.

8. Dizygotic twins come from two different secondary oocytes, each fertilized by two different sperms. • That mean they share only 50% of their DNA, much like all other singleton siblings.

9. They can be the same or opposite sexes. • They can as dissimilar as some singleton siblings. • But • They can look like identical twins, very rarely.

10. The embryos, fetuses and infants resulting from a di-zygotic pregnancy are called di-zygotic twins. • In other words twins resulting from two zygotes are di-zygotic twins. • They are also called fraternal twins. • They are almost two third of twin pregnancies.

11. The frequency of di-zygotic twins shows marked racial differences • but • The incidence of monozygotic twins is almost the same in all populations.

12. The frequency of di-zygotic twins increases with maternal age • but • The incidence of monozygotic twins is not affected with maternal age. • The fetal membranes and placentas vary according to the origin of the twins.

13. When more than two fetuses co-exist, • they may come from one secondary oocyte or • May come from more than one secondary oocyte or • be the result of combined mono-ovular and poly-ovular twining.

14. About 25% of identical twins are mirror image twins. • Their hair falls in opposite directions, • They have mirror image fingerprints • If one is right handed, the other is left handed.

15. Half identical twins occur when one secondary oocyte splits into two ootids before fertilization. • Each ootid is then fertilized by a separate sperm. • These twins share 75% of their DNA as they share the same DNA from ootids and different DNA from each sperm.

16. The incidence of multiple pregnancies has increased in these days due to excessive use of exogenous gonadotrophins. • These drugs are given to women with ovulatory failure who are treated for infertility.

17. Conjoined ("Siamese") twins are those that are attached at birth. Craniopagus Thoraco-abdominopagus Pyopagus

18. Conjoined twins can be separated from each other if they have no vital parts in common.

19. For example in craniopagus if the brain tissue is common it will be very difficult to separate the conjoined twins. • But if the two brains are separate and only the skull cavities communicate it will be easy to separate the two babies from each other.

20. Multiple pregnancies have higher risks of fetal morbidity and mortality than single pregnancies

21. Morbidity: • Morbid means diseased or unhealthy. • Morbidity is the condition of being diseased. • It is the sick rate. • It is the ratio of sick to well persons in a community.

22. Mortality: • Mortal means subject to death or destined to die. • Mortality is the quality of being mortal or the death rate.

23. The fetal morbidity and mortality progressively increases as the number of fetuses increases. • Study of twins is important in human genetics. It is useful for comparing the effects of genes and environments on the development of insan (human being)

24. Are there signs that determine whether a woman is more likely to have twins? Yes. Women who are of above average height and who have a large bone structure are more likely to have twins. Women who give birth at an older age (30+) Women who have taken fertility drugs Women who have been on birth control for several years. Women who were fraternal twins themselves, the chances of their having twins increase fivefold.

25. Di-zygotic twins • Poly-ovular multiple pregnancies result from fertilization of more than one secondary oocyte. • They are usually di-zygotic type of multiple pregnancies. • But it may be tri-zygotic type, tetra-zygotic and so on.

26. The embryos, fetuses and infants resulting from a di-zygotic pregnancy are called di-zygotic twins. • In other words twins resulting from two zygotes are di-zygotic twins.

27. Di-zygotic twins result from simultaneous shedding of two secondary oocytes and fertilization by two different sperms. • The resulting two zygotes have totally different genetic constitutions. • They share only 50% of their DNA, much like all other singleton siblings. • They can be the same or opposite sexes.

28. The infants born are not identical to each other. • They may be two brothers or two sisters or one sister and one brother. • So they have no more resemblance than any other sisters or brothers born at different times.

29. The only thing they have in common is that they were in their mother’s uterus at the same time. • They were womb-mates. • They are also called fraternal (brotherly) twins.

30. The two zygotes implant independently. They have their own placentae, amnions and chorionic sacs. • In approximately 40% cases the implantation of two zygotes is very close; the two placentas are thus so close that they may fuse together. • Similarly the walls of the chorionic sacs may also appose each other and fuse.

31. Occasionally, di-zygotic twins posses red blood cells of two different types, indicating that the fusion of two placentas was so close that red blood cells were exchanged. • This is called erythrocyte mosaicism.

32. The incidence of di-zygotic twins is 7 to 11 per thousand births. • Approximately two-thirds of twins are di-zygotic twins. • Di-zygotic twins show hereditary tendency. • The tendency of di-zygotic twins to repeat in families is evidence of hereditary influence.

34. This is a photograph of Mr Liaqat with his two dizygotic twin daughters. They are sitting in the lap of their father. Saba Liaqat is on right side (the side of her grandmother) and Ayesha Liaqat is on left side. • Saba Liaqat is blackish while Ayesh is whitish in color. Ayesha was born half hour before Saba.

35. A photograph of dizygotic sisters, Saba and Ayesha. Both are five year old in this photograph. Saba is one and half inch taller than Ayesha.

36. The incidence rate of di-zygotic twins increases with maternal age. • The frequency of di-zygotic twins shows marked racial differences. • Asians 1 in 500. • Caucasians 1 in 125. • Africans 1 in 20.

37. The recurrence risk in families is about three times than in general population. • If the first born are di-zygotic twins, the chances of twining or some other form of multiple births are approximately five times more in next pregnancy than in general population.

38. Studies show that the genotype of mother affects the frequency of di-zygotic twins, but the genotype of father has no effect on the frequency of di-zygotic twins. • Genotype: The entire genetic constitution of an individual.

39. Two secondary oocytes.

44. Two blastocysts have developed from two zygotes.

45. Each blastocyst implant separately. Each has its own placenta, amniotic cavity and chorionic cavity

47. The two blastocysts may implant like Ayat 9 i.e. both with cephalic presentation. • They may implant like Ayat 10 i.e. one with cephalic presentation and other with breach presentation. • Note in Ayat 9 and 10 placentas, chorions and amnions are separate.

48. The two blastocysts may implant like Ayat 11 i.e. both with cephalic presentation. • They may implant like Ayat 12 i.e. one with cephalic presentation and other with breach presentation. • Note in Ayat 11 and 12 the two placentas and chorionic sacs are fused but the amnions are separate.

49. Mono-Zygotic Twins • Mono-ovular multiple pregnancies result from fertilization of a single ovum. They are also called mono-zygotic type of multiple pregnancies. • The embryos, fetuses and infants resulting from a mono-zygotic pregnancy are called mono-zygotic twins. In other words twins resulting from one zygote are mono-zygotic twins.

50. Mono-zygotic twins are always of the same sex. They will be either two sisters or two brothers. • They are genetically identical and very similar in external appearance.