Date post: | 15-Oct-2014 |
Category: |
Documents |
Upload: | bivek-singh |
View: | 49 times |
Download: | 4 times |
Multiple Births
Multiple birthsMultiple births
Normally only one fetus is delivered at birth
Definition:Definition:It is delivery of more than one fetus by the end of
the same pregnancy (2,3,4,5,or more).
Types of Multiple birthsTypes of Multiple births
Monozygotic – multiple (typically two) fetuses produced by the splitting of a single zygote
Dizygotic – multiple (typically two) fetuses produced by two zygotes
Polyzygotic – multiple fetuses produced by two or more zygotes
Contd….Contd….
Two offspring – twins Three offspring – triplets Four offspring – quadruplets Five offspring – quintuplets Six offspring – sextuplets Seven offspring – septuplets Eight offspring – octuplets
Twins is a form of multiple birth in which the mother gives birth to two or more offspring from the same pregnancy, either of the same gender (sex), or of the opposite.
Types of twins
1/3 1/3 monozygotimonozygoti
cc100% Identical100% Identical
Dizygotic Dizygotic 2/32/3
Fertilization of two ova by two different sperms
Fertilization of one ovum by one sperm
Incidence Incidence Twins account for about 1% of all pregnancies, 66% dizygotic and 33% monozygotic. The incidence of dizygotic twins varies with
ethnic group maternal age parity method of conception
The incidence of monozygotic twins is similar in all ethnic groups and does not vary with maternal age or parity, but may be 2–3 times higher following IVF (In Vitro fertilization) procedures.
DIZYGOTIC TWINSDIZYGOTIC TWINS When two eggs are
fertilized by two separate sperm to create two embryos
FRATERNAL TWINS Fraternal twins are
always diamniotic / dichorionic
They never share membranes
Each have a placenta
Twin pregnancy Twin pregnancy
Monozygotic TwinsMonozygotic Twins One egg is fertilized by one
sperm but the zygote divides during early mitosis.
IDENITCAL TWINS They will have the same
exact DNA so they must always be the same gender.
There are several kinds of identical twins…It all depends on the timing of the separation of the fertilized egg.
Early Separation Early Separation (1-4 days after fertilization)(1-4 days after fertilization)
Each embryo will have its own amnion and chorion (diamniotic/dichorionic)
Each embryo will develop its own placenta
Average SeparationAverage Separation(4-8 days after fertilization)(4-8 days after fertilization)
Each embryo will have its own amnion but share a chorion (diamniotic/monochorionic)
This is the most common identical twin arrangement…
Sometimes they share a placenta, sometimes they will each have their own placenta. [Having their own placenta is better…]
Late SeparationLate Separation(8-12 days after fertilization)(8-12 days after fertilization)
The embryos will share both an amnion and a chorion (monoamniotic/monochorionic)
This occurs less that 1% of the time… There are usually complications (unequal
nourishment and cord entanglement) due to the fact that they share membranes – close supervision of a doctor is required
The two babies share a placenta.
Very Late SeparationVery Late Separation(12+ days after fertilization)(12+ days after fertilization)
The embryonic cell mass does not fully separate.. Conjoined twins
1 in very 200 identical twins are conjoined. 40% - 60% will be stillborn; 35% survive less than 24 hours.
EtiologyEtiology Two prominent theories explain the appearance of
conjoined twins, the theory of fusion and the theory of fission.
In the fusion theory, authors propose that the twins join secondary to late embryonic division.
in the fission theory, some authors feel there is instead an absence of complete embryonic division.
Teratodelphic conjoined twinsunited high on the body in the form of a lambda ():
Pelvidelphic Thoracodelphic
Teratodymic conjoined twins
twins united caudally in the form of a Y:
Iniodymic
Thoracodymic
Sternodymic
Types of mono-zygoticTypes of mono-zygotic
DiamnioticDichorionic
Diamniotic
MonochorionicMonoamniotic
MonochorionicConjoined
Determination of Zygosity and Determination of Zygosity and chorionicitychorionicity
Zygosity can only be determined by DNA fingerprinting “ amniocentesis, chorion villus sampling or cordocentesis”
Determination of chorionicity can be performed by ultrasonography and relies on the assessment of fetal gender, number of placentas, and characteristics of the membrane between the two amniotic sacs
Different-sex twins are dizygotic and therefore dichorionic, but in about two-thirds of twin pregnancies the fetuses are of the same sex and these may be either monozygotic or dizygotic
Similarly, if there are two separate placentas the pregnancy is dichorionic, but in the majority of cases the two placentas are adjacent to each other and there are often difficulties in distinguishing between dichorionic-fused and monochorionic placentas.