Multiple Pregnancy

Pregnancy involving more than one foetus.
- Monozygous ⇒ division of fertilised egg → identical (20% of twins).
- Dizygous ⇒ fertilisation of 2 ovum by 2 different sperm → non-identical (80% of twins). ALWAYS DCDA.
Chorionicity (number of placentas) → monochorionic (share single placenta) or dichorionic (two seperate placentas).
- Monochorionic Twins → can cause twin-twin transfusion syndrome.
  - One fetus (recipient) may receive the majority of blood from the placenta while the other fetus (donor) is starved of blood. Will be discrepancy between size of babies.
  - Recipient → can become fluid overloaded, with heart failure and polyhydramnios.
  - Donor → has growth restriction, anaemia and oligohydramnios.
  - Laser ablation may be needed to destroy connection between the two blood supplies.
Amnionicity (amniotic sacs) → monoamniotic (single amniotic sac) or diamniotic (two seperate amniotic sacs).
Time at which Zygote Divides → <day 4: DCDA, day 4-8: MCDA, day 8-12: MCMA, >day 13: conjoined.
Risk Factors → advanced maternal age, IVF, previous multiple pregnancy.
Occurs in 1 in every 80 pregancies.
Women with uncomplicated, multiple pregnancies should avoid travel by air once >32 weeks (37 weeks in singleton pregnancy).

Clinical Features

1st Trimester (up to 14 weeks) → incidental USS finding, hyperemesis, increased bHCG.
2nd Trimester (14-28 weeks) → large for dates, multiple foetal parts on abdominal examination.
Abdominal Examination → increased smphysial fundal height, multiple foetal parts, more than one foetal heartbeat.

Investigations