Multiple Pregnancy Flashcards
Determine zygosity and chorionicity in twins and understand the significance of both
Zygosity: the number of ova fertilised
Chorionicity: the number of placentas
Amnionisity: the number of gestational sacs
Dizygotic twins will always be DCDA because each zygote will require a gestational sac and a placenta.
For monozygotic twins, the type of twin pregnancy depends on the timing of the zygote’s split. The later the split the more complicated the pregnancy is.
If the embryo splits within 2-3 days after fertilisation then the twins are dichorionic-diamniotic (DCDA)
If between 3-8 days, then the twins are monochorionic-diamniotic twins (MCDA)
If the embryo splits between 8-13 days, then the twins are monochorionic-monoamniotic twins (MCMA)
If the embryo splits after 13 days, then the twins are monochorionic-monoamniotic conjoined twins
Dizygotic: 2 ova, 2 sperm, 2 placentas/ amniotic sacs = dichorionic (~70% of dichorionic)
Monozygotic: 1 ovum 1 sperm
If split before day 3, 2 P 2A = dichorionic (~30% of dichorionic)
If split day 3-5?, 1P 2A= monochorionic diamniotic
If day 8-13, 1P 1A= monochorionic monoamniotic (v rare) (includes conjoined twins- primitive streak?)
The later the split, the more shared structures.
Complications of multiple pregnancy
Antenatal
Antenatal
Maternal
Increased Sx of pregnancy (e.g. hyperemesis due to increased oestrogen, haemorrhoids, stretch marks)
Increased energy requirements (require much more protein)
Increased risk of developing pregnancy-related disease (pre-eclampsia, gestational diabetes, acute fatty liver of pregnancy)
Increased rates of APH due to placental abruption or placenta praevia
Anaemia - increased rates of iron deficiency (requires twice normal amount)
Increased rates of calcium deficiency
Foetal
Increased rate of malformations (genetic and structural)
Increased rate of IUGR
Increased rate of miscarriage and spontaneous termination of pregnancy
Increased rate of pre-term delivery
Intrapartum
Delivery
Increased rates of malpresentation
Increased rates of C/S
Foetal
Increased rates of foetal distress
Lower birth weight
Maternal consequences
Increased rates of needing to expedite delivery for maternal health concerns
Postpartum
Increased rate of PPH
Increased rate of postpartum depression
Complications restricted to only monochorionic twins:
TTTS (twin-twin transfusion syndrome)
MC twins share a single placenta with many intertwin anastomoses (AA, VV, AV). AV anastomoses occur when an unpaired artery and vein pierce the chorionic plate in close adjacency, facilitating unidirectional flow from donor to recipient twin. This can lead to transfusion if there are not enough AA anastomoses to counterbalance the AV anastomoses.
Types
TOPS
Discordant amniotic fluid volumes
Affects 15% of MC twins
100% mortality if untreated
Donor twin: anaemia, oliguria, hypovolaemia, oligohydramnios, IUGR, FDIU
Recipient twin: polycythaemia, polyuria, hypervolaemia, polyhydramnios, cardiomyopathy, FDIU
TAPS
Discordant intertwin Hb
Dx: MC twins without amniotic fluid volume discordance but with MCA peak systolic velocity discordance
Very similar to TOPS but involving smaller vessels
Slow transfer of blood, so there is no significant difference in amniotic fluid volume, but there is a difference in MCA PSV
Rx difficult since it involves small vessels - intrauterine foetal transfusions for the anaemic twin
Management
Monitoring - fornightly scans including MCA PSV
Amniodrainage +/- septostomy in TOPS
Serial amniodrainage involves drainage of polyhydramnios
Risk of membrane rupture
Does not cure the condition - only delays preterm delivery
Selective laser photocoagulation of placental vessel (SLPCV)
Interrupts transfer from donor to recipient, protecting either twin from hypotension in the event of co-twin death
Treatment is curative
TRAP sequence: twin reverse arterial perfusion
Selective IUGR
Death of a co-twin
Results in acute hypotension, anaemia, ischaemia, exsanguination
Mx: immediate delivery
Complications restricted to only monoamnionic twins: Cord entanglement Monochorionic twins are: Delivered earlier Much more likely to die Smaller More likely to be admitted to NICU/SCN More likely to get NEC More likely to get intraventricular haemorrhages
Mother Increased risk of -preterm labour: (gestation 35w4d MC, 36w5d DC) -perinatal mortality (MC>DC) -hypertension/preeclampsia -GD -APH -PPH -anaemia -depression (ante and postnatal) -marital disharmony
Foetus
-low birthweight (2060 MC vs 2282 DC)
-perinatal mortality (increased if <10th percentile and if discordance, especially if >30%)
MC:
-foetal anomalies
-selective growth restriction (discordance)
-conjoined (usually terminated), consequences of severe IUGR can be severe
-consequences of death of co-twin may be severe
-cardiac/other anomalies
MCDA:
-TTTS, TAPS, TRAP
MCMA:
-cardiac abnormalities much more
-cord entanglement
Principles of antenatal management of twin pregnancies?
Determine gestational age and chorionicity
First trimester US
DC twins have lambda sign
MC twins have T sign
Taking size of biggest twin (use largest CRL to date pregnancy)
Provision of information
Advice re: complications (see above)
Information re: specific risks (e.g. TTTS)
Discuss models of care (hospital/private obstetrician preferred over GP/shared care as higher risk pregnancy)
Support services (Australian Multiple Birth Association)
Monitoring during pregnancy
Will be managed in hospital with specialist obstetrician
More frequent than a singleton pregnancy
12 weeks: risk of T21
18 weeks: foetal anomaly scan
32 weeks: check position of placenta
MC twins: US every 2-3 weeks from 18 weeks
Checking for foetal growth discordancy
Monitoring for TTTS: bladder volume, amniotic fluid volume, MCA PSV
DC twins: US every 6 weeks from 20 weeks
Checking for foetal growth discordancy
Nutritional advice
Energy: increase each trimester by 600kJ above singletons
Protein: 175 g/day (much higher than previous advice)
Folate: 500 mcg/day (usual dose)
Calcium: 1200 mg/day (preferred increase in dietary intake, but can take supplements if necessary)
Iron: 30 mg/day (double of singleton requirements)
Weight gain: must put on substantially more weight to protect against premature delivery
Monitor for complications
Maternal
Pre-eclampsia - aspirin 100mg/day from 12-36 weeks, screen with regular BP and urine dipstick
GDM - need both early and late OGTT
APH
PPH
Anaemia
Depression - must stop working earlier
Foetal
Foetal anomalies
Growth issues
- screening +/- termination or multifoetal reduction to twins if >2
- Obstetrician based care
- provision of information/advice re complications (maternal, fetal)
- nutritional advice (energy, protein, folate, calcium, iron)
- aspirin 100mg/day wks 12-36 (preeclampsia)
- early GTT (14-16wks) if other RFs
- weekly or fortnightly USS of MC twins
Discuss timing and mode of delivery
Depends on chorionicity (to prevent perinatal mortality), presence of complications
Induction of labour
DCDA twins: 37 weeks due to risk of IUGR
MCDA twins: 36-37 weeks due to risk of TTTS
MCMA twins: 32-33 weeks due to risk of cord entanglement
Mode of delivery
Outcomes for twin 1 are better than that for twin 2
MCMA twins should be delivered early with C/S
No difference in outcomes for planned C-section v. planned NVD between 32-38 weeks if:
No foetal anomalies
Access to epidural and to theatre within 30 mins
Twin 1 must be cephalic
DCDA:
37+0 - 37+6 (beware late deaths due to foetal growth restriction).
MCDA:
36+0
Have a general understanding of twin-twin transfusion syndrome (TTTS)
TTTS (twin-twin transfusion syndrome)
MC twins share a single placenta with many intertwin anastomoses (AA, VV, AV). AV anastomoses occur when an unpaired artery and vein pierce the chorionic plate in close adjacency, facilitating unidirectional flow from donor to recipient twin. This can lead to transfusion if there are not enough AA anastomoses to counterbalance the AV anastomoses.
Types
TOPS
Discordant amniotic fluid volumes
Affects 15% of MC twins
100% mortality if untreated
Donor twin: anaemia, oliguria, hypovolaemia, oligohydramnios, IUGR, FDIU
Recipient twin: polycythaemia, polyuria, hypervolaemia, polyhydramnios, cardiomyopathy, FDIU
TAPS
Discordant intertwin Hb
Dx: MC twins without amniotic fluid volume discordance but with MCA peak systolic velocity discordance
Very similar to TOPS but involving smaller vessels
Slow transfer of blood, so there is no significant difference in amniotic fluid volume, but there is a difference in MCA PSV
Rx difficult since it involves small vessels - intrauterine foetal transfusions for the anaemic twin
Management
Monitoring - fornightly scans including MCA PSV
Amniodrainage +/- septostomy in TOPS
Serial amniodrainage involves drainage of polyhydramnios
Risk of membrane rupture
Does not cure the condition - only delays preterm delivery
Selective laser photocoagulation of placental vessel (SLPCV)
Interrupts transfer from donor to recipient, protecting either twin from hypotension in the event of co-twin death
Treatment is curative
