Classification or Types of Twin or Multiple Pregnancy

Twin or Multiple Pregnancy: Types and Classification

What is Multiple Pregnancy?

When more than one fetus simultaneously develops in the uterus, it is called multiple pregnancy.

Different Types of Multiple Pregnancy:

Varieties of multiple pregnancy are-

  • Twin (Commonest): Monozygotic/uniovular/monovular/identical and Dizygotic/binovular/fraternal.
  • Triplets (three fetus).
  • Quadruplets (four fetus).
  • Quintuplets (five fetus).
  • Sextuple (six fetus).
Types of twin or multiple pregnancy
Fig: Types of twin or multiple pregnancy

What is Twin Pregnancy?

Simultaneous development of two fetuses in the uterus is called twin pregnancy.

Different Types of Twin or Multiple Pregnancy:

Varieties of twin pregnancy are:

  • Dizygotic twins (commonest and it is 2/7 of twins). It is resulting from the fertilization two ova.
  • Monozygotic twins (1/3 of twins).


  • Diametric -diachronic twins.
  • Diamnoitic monchorinic twins.
  • Conjoined twins.
  • Monoamniotic monochorionic twins.

What is Conjoined Twins?

When two fetus is connected to each other with some part of body is called conjoined twins.

Types of Conjoined Twins:

There are four types of conjoined twins:

  1. Thoracopagus (commonest),
  2. Pyopagus (posterior fusion),
  3. Craniopagus (cephalic) ,
  4. Ischiopagus(caudal).

Criteria of Twins:

Dizygotic twins:

  • There are two placentae.
  • Each fetus is surrounded by a separate amnion and chorion.
  • The intervening membranes consists of 4 layers (amnion and chorion ‘and amnion).

Monozygotic twins:

  • The placenta is single
  • Each fetus is surrounded by separate amniotic sac with the chronic layer
  • The intervening membrane consists of two layers of amnion only.

Twin Transfusion Syndrome (TTS):

It is a clinic pathological state, exclusively met with in monozygotic twins where one twin appears to bleed into the other through some kind of placenta vascular anstomosis.

Clinical Manifestations of Twin Transfusion Syndrome (TTS): 

It occurs when there is haemodynamic imbalance due to unidirectional deep arteriovenous anastomose–

  • As a result the receptor twin becomes larger with hydramnios, polycythemic, hypertensive and hypervolaemic.
  • At the expensive of the donor twin which becomes smaller with oligohy dramni os anemic, hypotensive and hypovolaemic.
  • The donor twin may appear “stuck” due to severe oligohydramnios.
  • Difference of haemoglobin concentration between the two, usually exceeds 5mg% and estimated fetal weight discrepancy is 25% or more.
  • The smaller twin generally have got better outcome.
  • Perinatal mortality of TTS is about 70%.

You can read: Pregnancy Sign, Symptoms and Confirmation Test

Diagnosis of Twin Transfusion Syndrome (TTS): 

  • By USG with droppler blood flow study in the placental vascular bed.

Treatment of Twin Transfusion Syndrome (TTS):

  • Repeated amniocentesis: To control polyhydramnios in the receptor twin.
  • Laser photocoagulation: To interrupt the anaestomotic vessels on the chorionic plate can give some success.

More questions related to this article:

  1. What do you mean by multiple pregnancy?
  2. Define the term multiple pregnancy.
  3. Define multiple pregnancy.
  4. What are the types of multiple pregnancy?
  5. What do you mean by twin pregnancy?
  6. What are the types of twin pregnancy?
  7. What are the varieties of twin?
  8. Mention the criteria of twins.
  9. What do you mean by conjoined twins?
  10. What do you mean by twin transfusion syndrome?
  11. What is the treatment of twin transfusion syndrome?
  12. What is the diagnosis of twin transfusion syndrome?
  13. What are the clinical manifestations of twin transfusion syndrome?

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