Twinning and pregnancy

• Multiple Pregnancy


  The presence of more than one fetus in the gravid uterus

  
• Types of Multiple Pregnancy

  • Twins (two fetuses)
  • Triplets (three fetuses)
  • Quadruplets (four fetuses)
  • Quintuplets (five fetuses)
  • Sextuplets (six fetuses)

  
• Conjoined twins


  1 in 60,000 incidence
• Monozygotic twins


  Worldwide incidence of 1 in 250
• Dizygotic twins


  Incidence is variable and increasing
• Factors affecting incidence of multiple pregnancy

  • Race (most common in Negroes)
  • Increased maternal age
  • Multiparity
  • Family history
  • Nutritional status (well nourished women)
  • Assisted Reproductive Technology
  • Stopping Oral Contraceptive Pills
• Varieties of Twins


  • Dizygotic (two-thirds)
  • Monozygotic (one-third)
• Genesis of Dizygotic Twins

  Fertilization of two ova by two sperms

  
• Genesis of Monozygotic Twins

  1. Up to 3 days - diamniotic-dichorionic

  2. Between 4th & 7th day - diamniotic monochorionic (most common)

  3. Between 8th & 12th day - monoamniotic-monochorionic

  4. After 13th day - conjoined / Siamese twins

  
• Types of Conjoined Twins

  • Ventral: Omphalopagus, Thoracopagus, Cephalopagus, Caudal/ ischiopagus
  • Lateral: Parapagus
  • Dorsal: Craniopagus, Pyopagus

  
• Superfecundation


  Fertilization of two different ova released in the same cycle
• Superfetation


  Fertilization of two ova released in different cycles
• Differences between Monozygotic and Dizygotic Twins

  • Monozygotic: 1 ovum + 1 sperm, Same sex, Identical features, Single or double placenta, Same genetic features, DNA microprobe - same
  • Dizygotic: 2 ova + 2 sperm, Same or opposite sex, Fraternal resemblance, Double or fused placenta, Different genetic features, DNA microprobe - different

  
• Differences in chorionicity with single placenta

  • D/D (fused placenta): Monozygotic or dizygotic, Thick dividing membrane > 2mm, Twin peak / lambda sign
  • M/D: Monozygotic, Thin dividing membrane 2mm or less, T sign

  
• Maternal Complications of Multiple Pregnancy

  • During pregnancy: Miscarriages, Hyperemesis gravidorum, Anaemia, Pre-eclampsia (25%), Hydramnios (10%), Antepartum hemorrhage, Cholestasis of pregnancy, Malpresentations, Preterm labour (50%)
  • During Labour: Pre-labour rupture of the membranes, Cord prolapse, Incoordinate uterine contractions, Increased operative interference, Placental abruption after delivery of 1st baby, Postpartum haemorrhage
  • During puerperium: Subinvolution, Infection, Lactation failure

  
• Fetal Complications of Multiple Pregnancy

  • Spontaneous abortion, Single fetal demise, Low birth weight (90%), Prematurity, Fetal growth restriction, Discordant growth, Congenital anomalies, Twin to Twin Transfusion Syndrome, Twin Reversed Arterial Perfusion Syndrome, Cord entanglement and compression, Locked twins, Asphyxia, Stillbirth

  
• Monoamniotic twins have high perinatal morbidity and mortality
• Indications for Caesarean Section in Multiple Pregnancy

  • Non cephalic presentation of first twin
  • Monoamniotic twins
  • Conjoined twins
  • Locked twins
  • Other obstetric conditions
  • Second twin - incorrectible lie, closure of cervix