Abnormal Development - Twinning: Difference between revisions

Revision as of 09:41, 15 June 2010

Introduction

While singleton human births are the most common, there are also several different forms of twinning that may arise in the early weeks (first two weeks) of development. The two major twinning forms are monozygotic (from one fertilised egg and a single spermatazoa) or dizygotic (from two eggs fertilised by two different spermatazoa).

In addition to the zygosity, the additional twinning classifying terms refer to the type of placenta and fetal membranes, either separate or shared by the twins. Twinning has both a higher incidence of mortality in twins, due mainly to preterm delivery, and of incidence of birth defects.

Twinning Prevalence

The prevalence of spontaneous livebirth monozygotic twinning is relatively constant, with variability in dizygotic twinning around the world.

Asia 6 in 1000
Europe/USA 10-20 in 1000
African-Americans 26 in 1000
Africa 40 in 1000
Japan 1 in 250
Nigeria 1 in 11

Monozygotic conjoined twins - 1 in 100,000 births (more female)

United States of America - 2.7% of all confinements resulted in a multiple birth in 1996 (U.S. Census Bureau, 1999, p.80)

New Zealand - 1.6% in 1998 (Statistics New Zealand, 2000, p.70)

Australia - 1.5% in 1998 (ABS, see below)

Dizygotic Twinning

Dizygotic twins (fraternal, non-identical) arise from separate fertilization events involving two separate oocyte (egg, ova) and spermatozoa (sperm).

Monoygotic Twinning

Monoygotic twins (identical) produced from a single fertilization event (one fertilised egg and a single spermatazoa, form a single zygote), these twins therefore share the same genetic makeup. Occurs in approximately 3-5 per 1000 pregnancies, more commonly with aged mothers. The later the twinning event, the less common are initially separate placental membranes and finally resulting in conjoined twins.

Week		Week 1							Week 2
Day	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14
Cell Number	1	1	2	16	32	128				bilaminar
Event	Ovulation	fertilization	First cell division	Morula	Early blastocyst	Late blastocyst Hatching	Implantation starts			X inactivation

Monoygotic Twin Type		Diamniotic Dichorionic			Diamniotic Monochorionic			Monoamniotic Monochorionic			Conjoined

Table based upon recent Twinning Review.^[1]

References

↑ <pubmed>12957099</pubmed>

Reviews

Articles

Search Pubmed

Search Pubmed: Twinning

Glossary Links

Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link

Cite this page: Hill, M.A. (2024, April 20) Embryology Abnormal Development - Twinning. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Abnormal_Development_-_Twinning

What Links Here?

[1] <pubmed>12957099</pubmed>

[1]

@@ Line 4: / Line 4: @@
 In addition to the zygosity, the additional twinning classifying terms refer to the type of placenta and fetal membranes, either separate or shared by the twins. Twinning has both a higher incidence of mortality in twins, due mainly to preterm delivery, and of incidence of birth defects.
+==Twinning Prevalence==
+The prevalence of spontaneous livebirth monozygotic twinning is relatively constant, with variability in dizygotic twinning around the world.
+* Asia 6 in 1000
+* Europe/USA 10-20 in 1000
+* African-Americans 26 in 1000
+* Africa 40 in 1000
+* Japan 1 in 250
+* Nigeria 1 in 11
+Monozygotic conjoined twins - 1 in 100,000 births (more female)
+United States of America - 2.7% of all confinements resulted in a multiple birth in 1996 (U.S. Census Bureau, 1999, p.80)
+New Zealand - 1.6% in 1998 (Statistics New Zealand, 2000, p.70)
+Australia - 1.5% in 1998 (ABS, see below)
 ==Dizygotic  Twinning==