Twin Gestation Flashcards
What is twin gestation
Multiple Pregnancy: two or more fetuses in the uterus
Risk Factors for Multiple Gestation
*Assisted reproduction technique (IVF, ovulation induction)
*High parity
*Black race
*Maternal family history Nutritional influence
*Tall and obese women
*Following discontinuation of contraceptive
What are the classifications
*Based on number of fetuses :twins, triplets, quadruplets
*Based on number of fertilized eggs: zygosity
*Based on number of placenta: chorionicity
*Based on number of amniotic cavities: amnionicity
Non-identical (Dizygotic or Fraternal) Twins - 80% of cases what are the components
- They are dizygotic, dichorionic, and diamniotic
- The dividing membrane is thick (3 layers)
- Fetuses may have the same or different sex
- Arises spontaneously from release of 2 eggs at ovulation both of which are fertilized
- Highest incidence si among Africans especially the Yoruba ethnic group
Identical (Monozygotic) Twins- 20% of cases
- May be monochorionic or dichorionic
- Majority of the monochorionic are diamniotic but the dividing membrane is thin 1( layer)
- Fetuses are always same sex
- Incidence is in 250, it is not influenced by race, family history or parity
- Arises from a single fertilized ovum that splits into two identical structures
What are Types of monozygotic twin formed depend on when after conception the split occurs:
- Within 3days: dichorionic diamniotic
- Between day 4and 8: monochorionic diamniotic
- Between day 9and 12: monochorionic monoamniotic
- After day 12: conjoined or Siamese twin (e.g thoracophagus, craniopagus)
What to note about twin gestation
Note: al monochorionic pregnancy are monozygotic but not al dichorionic pregnancy are dizygotic
