High Risk Pregnancy

Question 1

Risk factors for multiple pregnancy

Answer 1

• Assisted conception (IVF/ovulation induction)
• Maternal age (4x greated chance at age 37 than age 18)
• Ethnic origin (West African)
• FHx (maternal inheritance)

Question 2

Terminology in multiple pregnancy

Answer 2

• Zygosity = number of fertilised eggs
• Chorionicity = number of placentas
• Amnioncity = number of sacs

Question 3

Dizygotic twins

Answer 3

• Most common
• 2 eggs + 2 sperm
• May look identical but not any more genetically identical than any pair of siblings
• Genetic predisposition

Question 4

Monozygotic twins

Answer 4

• One fertilized egg which splits
  
  • Before day 4 - prior to chorion development, dichorionic, diamniotic, may have seperate or fused placenta, can’t distinguish from dizygotic twins on scan
  • Day 4-8 -prior to amnion development, monchorionic, diamniotic
  • From day 9 - after amnion development, monochorionic, monoamniotic, very rare, if after day 13 risk of conjoined twins

Question 5

Risks of multiple pregnancy

Answer 5

• Maternal (all complications increased by increased fetal/placental number)
  
  • Antenatal
    
    • Hypereesis gravidarum
    • Pre-eclampsia
    • Gestational diabetes
    • Placenta praevia
  • Intrapartum
  • Post-partum
    
    • Haemorrhage (tone reduced in uterus, double the placentas and two babies cause more trauma)
    • Depression and bereavement
    • Anxiety
    • Relationship difficulties

Question 6

Risks of multiple pregnancy - fetal

Answer 6

• Fetal
  
  • Miscarriage
  • Congenital anomaly (risk doubled)
  • Growth restriction
  • Pre-term delivery
    
    • Average 37 weeks for twins, 34 weeks for triplets
    • Increased proportion delivery <30 weeks
  • Specific complications of monozygotic twins
    
    • Acute transfusion
    • Twin-twin transfusion syndrome
    • Twin reversed arterial perfusion sequence

Question 7

Prenatal diagnosis of complications

Answer 7

• Ultrasound
  
  • Determination of chorionicity
  • Nuchal translucency preferred screen for aneuploidy
  • Monitoring fetal growth if high risk of IUGR
• Invasive procedures
  
  • Amniocentesis
  • Chorionic villus sampling

Question 8

Delivery of multiple pregnancies

Answer 8

• Elective delivery at 37 weeks for DCDA twins and 36 weeks for MCDA twins
• Analgesia for mum
• Monitoring during labout (maternal BP, fluids, continuous CTG, abdominal and fetal scalp electrode)
• First tin delivered as normal, cord is clamped, experienced obstetrician determines presentation of second twin - sometimes vaginal delivery and sometimes CS

Question 9

Specific complications of monozygotic twins

Answer 9

• Acute transfusion
  
  • Death of one twin in utero leads to increased risk of hypoxic-ischaemic injury in survivor dur to acute transfusion from healthy to dying twin - delivery expedited to treat if not IUD or monitoring increased if IUD
• Twin-twin transfusion syndrome
  
  • Chronic net shunting from one twin to the other - diagnosis using US, managed using fetoscopic laser ablation of anastamoses or cord occlusion, 2/3 have dead or brain damaged baby
    
    • Donor twin (growth restricted, oliguric, anhydramnios)
    • Recepint twin (polyuric, polyhydramnios, cardiac problems, hydrops)
• Twin reversed arterial perfusion sequence
  
  • Two cords linked by big arterio-arterial anastamoses, retrograde perfusion
  • Pump twin and perfused twin

Question 10

Monoamniotic twin complications

Answer 10

• Almost all develop cord entanglement
• Lots of placental anastamoses