Twins

Question 1

Management of multiple pregnancy

Answer 1

1. Multidisciplinary team NB including Obstetricians, midwives, Sonographers, dieticians, Perinatal mental health practitioners
2. Education NB:
   DCDA twins:
   - Increased risks of all obstetric complications except post-dates and macrosomia
   -Maternal: hyperemesis, anaemia, miscarriage, GDM,
   PIH, PET, PPROM, APH, polyhydramnios, maternal
   mortality, PND
   - Delivery: instrumental, CS, PPH
   Fetal – congenital anomalies, IUGR, prematurity, FDIU,
   neonatal death
   MCDA twins:
   - All complications associated with DCDA twins
   - Twin-twin transfusion syndrome (TTTS) – 15%
   - Fetal death of one twin and sequelae
   - Twin reversed arterial perfusion (TRAP) sequence
3. All routine antenatal bloods and Ix:
   - FBE, U and E, UMCS, Viral screen/serology, Blood group and antibody screen, dating ultrasound: Date by larger CRL (Between 11-14 weeks)
4. Determine Chorionicity at 10-14 weeks with experienced sonographer
   DCDA:
   - Two placentas
   - Thick dividing membrane (>2mm)
   - Lambda sign (wedge of placenta between dividing membranes)
   MCDA:
   - Thin dividing membrane
   - T sign (right angle between placental tissue and membrane
5. Aneuploidy screening:
   - In twin pregnancies, the sensitivity of CFTS generally ranges from 72%-80%.29 The use of nasal bone
   assessment can improve the sensitivity of CFTS in twin pregnancies to 89% for a fixed 5% false positive
   rate.
   - The performance of all screening tests that incorporate maternal blood biomarkers is reduced in twin
   pregnancies compared with singletons due to the inherent biological complexity of multiple gestation.
   -Laboratories need specific clinical details to reliably calculate the likelihood of aneuploidy from
   biochemical data. These include:
   - whether both twins are alive and, if not, the gestation of demise of the late twin
   - the chorionicity (monochorionic /dichorionic)
   - the crown rump length (CRL) of both fetuses.
   - In twin pregnancies, cfDNA-based screening may be offered with appropriate pre-test counselling regarding an increased test failure rate, and less available performance data compared with singletons. Sensitivity of 100% for T21
   - In triplet and higher order pregnancies, screening for chromosome conditions should be performed with first trimester ultrasound markers
   (i.e. nuchal translucency thickness and nasal bone assessment +/- additional markers at 11-13 weeks).
6. Supplementation:
   - High dose Folic Acid
   - Vitamin D
   - Iodine
   - Consider Fe based on Ferritin levels
7. PET prophylaxis with low dose ASA/Ca: If one additional moderate risk factor (ie nulliparous,
   age>=40, pregnancy interval >10 years, BMI >=35, family
   hx PET)
8. Consider early GTT
9. Education re safe weight gain in pregnancy with twin specific charts
10. Tertiary Morphology US:
    DCDA twins: Double risk of anomalies due to 2 fetuses
    MCDA twins: 2-3 x risk of DC twins
11. Growth surveillance with DVP and Dopplers:
    DCDA: 4-weekly from 24/40, Growth discordance >25%
    suggests IUGR
    MCDA: 2-3 weekly from 12/40 and fortnightly from 18/40 with MCA PSV at each scan from 24/40
12. Delivery:
    - Timing DCDA 37-38 weeks
    MCDA 36-37 weeks
    - Mode:
    DCDA: Vaginal birth safe under certain
    circumstances (first twin cephalic, growth discordance <20-25% if larger twin 2, no evidence fetal compromise)
    MCDA:Safety of vaginal delivery controversial due to risk of intrapartum TTTS
    - Send placentas for Histology
    - Active management of third stage with IM syntocinon and Oxytocin 40u Infusion
13. Postnatal
    - Lactation support
    - Monitor for PND
    - Contraception

Question 2

Counselling re MOD

Answer 2

• There are some circumstances in which a caesarean section is recommended
• Non-vertex presentation of twin I
• Growth discordance >20% with larger 2nd twin, or 2nd twin >500g larger
• Fetal compromise in either twin
• If above conditions met, vaginal birth preferable for DCDA twins and reasonable
  (although controversial) for MCDA
• Evidence has shown no increase in neonatal death or neonatal morbidity for twins with planned vaginal birth, however underpowered
• Other studies have shown small increase in perinatal mortality and morbidity for twin 2
• Possible intrapartum risks
• Cord prolapse
• Placental abruption
• Need for code green caesarean delivery of twin 2
• PPH
• To attempt a vaginal birth, mother must be agreeable to
• IV access
• CEFM
• Epidural

Question 3

Discuss vaginal birth procedure

Answer 3

Vaginal birth procedure
* Hospital delivery with 24 hour access to anaesthetics, Neonatology and theatre
* Planned delivery via induction
* IV access, group and hold
* CEFM, with FSE twin 1
* Elective epidural to aid with internal manoeuvres for twin 2
* Ultrasound in the room
* Preparation of syntocinon infusion to shorten inter-twin delivery interval (10u in 1l or syringe driver and titrated according to IOL policy)
- Aim for <30 minutes
* Internal podalic version for delivery of breech twin 2
- Reach into uterus and grab fetal foot (aiming to keep membranes intact)
- Deliver to vaginal introitus and follow with other foot
- Amniotomy once engaged, routine breech delivery with MSV or forceps for aftercoming head
* Active management of third stage

Question 4

Discuss diagnostic Aneuploidy testing Twins

Answer 4

• Chorionicity should be known
• Document twin presentation, location, sex, placental location when multiple samples taken in case selective termination required
• CVS
  o Single sample for MC twins
  o For DC twins need to avoid contamination, so consider TA/transcervical approach, location close to cord insertion
  o 6% chance of needing follow-up amniocentesis
  o 2% fetal loss
• Amniocentesis
  o 2 samples from 2 sacs with different needles
  o Consider single sample for MC twins with no evidence of abnormality, however discordant karyotype has been reported
  o 1-2% fetal loss

Question 5

Fetal Growth Discordance

Answer 5

• Causes
  o Poor placentation
  o Fetal anomaly/aneuploidy in one twin
  o Infection
  o TTTS
• Management
  o TORCH
  o Amniocentesis
  o Growth surveillance
  o Celestone
• Delivery planning
  o Balance risk of compromise of smaller twin with iatrogenic prematurity of
  larger twin

Question 6

Threatened Preterm labour

Answer 6

Complicates 50% of twin pregnancies
* Prevention
o No evidence to support hospitalisation, bed rest, prophylactic tocolysis, progesterone (PV or IM) or cerclage in multifetal pregnancies
o Arabin pessary
- Protwin study showed reduction in risk of preterm delivery when pessary used in twin pregnancies with short cervix
* Management
o Tocolytic therapy
- Can be used as in singleton pregnancies, however with close observation of maternal haemodynamic status (increased hypovolaemia and cardiac demands)
o Steroids
- Equivalent benefit to singleton pregnancies

Question 7

Single fetal demise

Answer 7

• Miscarriage risk
  o 1% singleton
  o 2% DC
  o 10% MC
• Stillbirth risk
  o 3.5 fold in DC
  o 7 fold in MC
• Dichorionic twin death
  o Death of one twin more common than both
  o Risk of death or disability in surviving twin 5-10% (prematurity related)
• Increased risk preterm labour
  o Management
• Close growth surveillance of surviving twin
• Monitor maternal coags for evidence of DIC
• Monochorionic
  o Highest fetal loss rate is <24/40
  o Death of both twins is more common
  o Risk of subsequent death in surviving fetus is 10-25%
  o Risk of cerebral ischaemia in surviving fetus is 25-45%
• Due to hypotension following fetal demise and exsanguination of surviving twin into dead twin’s uteroplacental circulation via anastomoses
  o Need to monitor surviving twin for development of cystic changes
• Offer TOP if evidence of severe ischaemia
  o Aim to delay delivery as long as possible (unless cause of death ie PET persists)

Question 8

Twin to twin Transfusion

Answer 8

Definition: A condition unique to monochorionic pregnancies whereby anastomoses allow
transfusion of blood from one fetus to another
Incidence: 15% of MCDA pregnancies
Pathophysiology
* Presence of arteriovenous anastomosis, without arterioarterial anastomosis that can balance the unidirectional flow
* Donor twin becomes hypovolaemic with oligohydramnios, and the recipient twin becomes fluid overloaded and polycythaemic with polyhydramnios
Diagnosis
* Detected on routine serial ultrasound scans fortnightly
* Quintero staging
Stage 1: Oligohydramnios (DVP<=2cm) in donor, polyhydramnios (>=8cm) in recipient
Stage 2: Stage 1 with absent bladder in donor
Stage 3: Stage 2 with critically abnormal dopplers in either twin
- AREDF in UA
- Reverse flow in DV
- Pulsatile umbilical venous flow
Stage 4: Stage 3 with ascites, pericardial effusion, pleural effusion, scalp oedema or overt hydrops present in recipient twin
Stage 5: Fetal demise of one or both twins
Management
* Requires referral to MFM unit
* Historical management
- NSAIDs
- Amnioreduction
- Septostomy
- None of these treat underlying pathology
* Current management
- Fetoscopic laser photocoagulation of the intertwin anastomoses
§ Preferred method of treatment for stage II-IV TTTS
§ Improved survival of one twin to 6 months compared to amnioreduction
§ Can selectively ablate anastomoses, or ablate along entire vascular equator (this method may reduce recurrence)
§ Risk of PPROM, infection, preterm labour, TAPS
o Cord occlusion (selective reduction)
- Considered for early onset TTTS (ie prior to 20/40)
- Performed with fetoscopic ligation, laser coagulation, cauterisation
Prognosis
* Untreated TTTS stage 3 or above in midtrimester has 10% survival rate
* 75% of untreated TTTS stage 1 will remain stable or improve
* Following laser photocoagulation, 88% chance of survival of at least one fetus
o Major neurological disability in survivor of 5-10%

Question 9

TAPS and TRAP

Answer 9

Twin Anaemia Polycythaemia Sequence (TAPS)
* Haemoglobin differences between MC twins without difference in DVP
* Caused by slow transfusion from donor to recipient
* Incidence: 5% of MC pregnancies, 10% following laser photocoagulation
* Diagnosis: MCA PSV >1.5 MoMs in donor, <1.0 MoMs in recipient
* Onset: >26/40 if spontaneous or <5/52 following laser procedure

Twin Reversed Arterial Perfusion (TRAP) Sequence
* Acardiac twin
* Normally formed donor supports circulation of both twins, resulting in cardiomegaly and high output cardiac failure
- Recipient twin receives perfusion preferentially to lower body via iliac vessels
* Risk of death or neurological injury in donor twin if untreated
* Manage with second trimester ablation of umbilical vessels in recipient twin
- 90% survival of donor following this procedure

Question 10

Selective Reduction

Answer 10

• Rationale: Selective reduction in higher order pregnancies may reduce preterm birth and
  sequelae (ie cerebral palsy) and maternal risks ie PET/GDM/PPH
• Risks

1. Singleton
   - Perinatal mortality 7/1000
   - Birthweight<1000g <1%
   - Cerebral Palsy 2/1000
2. Twins
   - Perinatal mortality 43/1000
   - Birthweight <1000g 10%
   - Cerebral Palsy 10/1000
3. Triplets
   - Perinatal Mortality 145/1000
   - Birthweight <1000 30%
   - Cerebral palsy 40/1000
   * Triplet pregnancies have a 20-fold increase in perinatal mortality and CP compared to singletons

Procedure for selective reduction
* Performed 10-14/40
- Adequate size
- CVS usually has been performed prior
* Selection of any anomalous or smallest fetus
* KCl injected into thorax under US guidance (not suitable for MC twins)
* US 1/24 later to confirm asystole
* Fetus left in situ to dessicate

Selective termination
* Procedure performed later in gestation, usually for structural or genetic anomalies
* Intracardiac KCl injected if DC
* Umbilical cord interruption if MC

Outcome
* Reduction of triplets to twins reduces perinatal mortality, preterm birth and increases take home baby rate
- 5% loss rate (same as unreduced twins)
* Risk of termination of incorrect fetus (in cases of aneuploidy or anomaly), preterm labour, infection, haemorrhage, DIC due to RPOC