Multiple Pregnancy

Question 1

What are the risk factors for multiple pregancies?

Answer 1

• Advanced maternal age
• IVF
• Previous multiple pregnancy
• Hereditary factors

Question 2

How do identical and non-identical twins form?

Answer 2

• Identical = division of fertilised egg (20%)
• Non-identical = fertilisation of 2 ovum by 2 different sperm (80%)

Question 3

What terms are used to describe monozygous twins?

Answer 3

• Split 0-4 days → dichorionic diamniotic → 2 placenta and 2 amniotic sacs (25%)
  
  • S/S: λ sign (triangular placental tissue projection into base of membranes)
• Split 4-8 days → monochorionic diamniotic → 1 placenta and 2 amniotic sacs (75%)
  
  • S/S: T-sign (no placental tissue projection into base of membranes)
• Split 8-12 days → monochorionic monoamniotic → 1 placenta and 1 amniotic sac (1%)
  
  • S/S: T-sign, ‘entangled cords’
• Split >12 days → conjoined twins (<1%)

Question 4

What are the signs and symptoms of multiple pregnancies?

Answer 4

• 1^st trimester = incidental on USS, hyperemesis - increased βHCG
• 2^nd trimester = large for dates, multiple parts on abdominal exam
• Abdominal exam = increased SFH, multiple parts, >1 FH

Question 5

What is the antenatal management of multiple pregnancies?

Answer 5

• FBC at 20-24w → extra supplementation of iron or folic acid and repeat at 28 weeks
• BP → increased chance of eclampsia)
• OGTT → increased likelihood of diabetes
• Repeat scans (every 2 weeks for shared placenta and 4 weeks if not)
• Serial USS for foetal growths
  
  • Monochorionic twins: scan at 12, 16 and every 2 weeks until delivery
  • Dichorionic twins: scan at 12, 20 and every 4 weeks until delivery
  • Monochorionic triplets: scan at 12, 16 and every 2 weeks until delivery
  • Dichorionic triplets: scan at 12, 16 and every 2 weeks until delivery
  • Trichorionic triplets: scan at 12, 20 and every 4 weeks until delivery

Question 6

What is the pre-term birth management of multiple pregnancies?

Answer 6

• 60% of twin pregnancies
• Preventing Preterm Birth if indicated
  
  • Bed rest at home or in hospital
  • IM or vaginal progesterone
  • Cervical cerclage
  • Oral tocolytics
  • Corticosteroids if preterm birth is likely

Question 7

How should the timing of birth be managed in multiple pregnancies?

Answer 7

• 60% of twin pregnancies result in spontaneous birth before 37 weeks
• Offer elective birth if
  • Uncomplicated monochorionic twin - from 36 weeks (after course of steroids)
  • Uncomplicated dichorionic twin – from 37 weeks
  • Uncomplicated triplet – from 35 weeks (after a course of steroids)
  • If declined → weekly obstetrician appointments

Question 8

What are the complications for foetus in multiple pregnancies?

Answer 8

• IUGR or discordant IUGR
  
  • Monitored with EFW discordance (not SFH) - difference in size >20% is an indicator of IUGR
  • Aim to repeat scans at least every 4 weeks
• Down Syndrome - same risk for individual but higher overall
• Structural Abnormalities
• Twin-to-Twin Transfusion Syndrome (TTTS)
• Intra-uterine death (IUD)

Question 9

What are the complications for mothers with multiple pregnancies?

Answer 9

• Pre-eclampsia
• Hyperemesis gravidarum - more bHCG
• GDM - more placental lactogen and placental steroids so more likely to tip into diabetes
• APH, PPH
• Anaemia and thrombocytopaenia - more required to sustain the two children

Question 10

Define TTTS.

Answer 10

In twins who share one placenta. If the vessel connections within the placenta are not evenly dispensed and there is an imbalance in the blood exchange between the twins.

Question 11

What is the pathogenesis of twin-to-twin transfusion syndrome?

Answer 11

Direct arterial to venous flow in placenta

• Donor baby SGA / oligohydramnios
• Recipient baby LGA / polyhydramnios
• Diagnosed if >25% difference of EFW
• Risk to recipient baby > donor baby
  
  • More blood → More cardiac strain → Hydrops fetalis

Question 12

What are the signs and symptoms of TTTS?

Answer 12

• Monochorionic pregnancy
• Sudden abdomen size increase
• SOB
  
  • Start diagnostic monitoring with USS from 16-24 weeks on a 2-weekly basis

Question 13

What is the management of TTTS?

Answer 13

• <26w = foetoscopic laser ablation of vascular anastomoses
• >26w = delivery if 1+ twin is in danger and by 34-37w in best case

Question 14

Describe selective growth restriction/disconcordant IUGR?

Answer 14

• Selective reduction may be an option if it is early
• Surveillance scans every 2 weeks
• Abnormal Doppler waveforms = indication for delivery