Multiple Pregnancy Flashcards
Incidence of monozygous twin
3-5:1000
Triplet birth rate
0.24: 1000 live births
Twin birth rate
15.8 :1000 LB
Perinatal mortality : twins
37 : 1000
3 times higher than singleton
Perinatal mortality: triplets
52: 1000
Perinatal mortality: higher order
231: 1000
Cerebral palsy in twins
8 fold
Cerebral palsy triplets
47 fold
What percentage if monozygotic twins are DCDA
25-30%
What percentage of monozygotic twins are monochorionic
75%
What cleavage phase results in MCMA
Cleavage between days 8 and 13
Most reliable time to determine chorionicity
10-13 weeks
Ultrasound features if monochorioninc twin (4)
- early pregnancy 1 placental mass
- T sign (thin intertwin membrane)
- twin membrane <1.8mm
-non discordant sex
Incidence of congenital malformation in monozygotic twins compared to dizygotic twins
3 fold compared to dizygotic
When should screening for TTTS begin?
16 weeks
How often should ultrasounds be performed in TTTS screening
Baseline: Every 2 weeks from 16 weeks
When is the most common time for TTTS to develop
16 - 24 weeks
(Only 1% of cases happen after 24 weeks)
When should fetal surveillance begin for DCDA twins
24 weeks
How often should ultraosund be done in DCDA
Baseline: every 4 weeks
What has been proven to prevent preterm birth in multiple pregnancy?
Nothing.
Studies have found no clinical benefits of bedrest, tocolytics, progesterone and cerclage in multiple pregnancies.
What are maternal complications of twin pregnancies
Antepartum (3)
- preeclampsia
- anemia
- gestational diabetes mellitus
What screening should be offered in twin pregnancies?
Aneuploidy
- first trimester combined (NT, hcg, pappa)
- integrated screening ( NT + t1 screen + t2 screen)
- cfdna ( 99% sensitive for trisomy 21)
Advantages of NIPT (4)
- Higher detection rate
- High negative predictive value for trisomy 21
- Lower false positive rate
- Less dependent on gestational age
What are the most common complications of monochorionic placentation
- TTTS
- TRAP
What percentage of MC are complicated by TTTS
10-15%
What is the postulated pathophysiology of TTTS
The presence of deep unidirectional flow through arterio-venous communications and minimal or no superficial bidirectional flow
How does oligohydramnios occur in TTTS
Hypovolemia of the donor twin results in activation of the renin- angiotensin system resulting in
Vasoconstriction, oliguria, iugr
What system is used to classify TTTS
Quintero classification
Stage 1 TTTS
Oligohydramnios (<2cm DVP) one twin
Polyhydramnios (>8cm DVP) other twin.
Both bladders visible
Stage 2 TTTS
Bladder absent for donor twin
Stage 3 TTTS
Abnormal dopplers in either twin
Stage 4 TTTS
Fetal hydrops in either twin
Stage 5 TTTS
Death if one or both twins
What is the fetal mortality for untreated moderate-severe TTTS
up to 90%
What are the neonatal long term implications of TTTS (3)
- cardiac
- renal
- neurological complications
Treatment options for TTTS (5)
- laser ablation
- serial amnioreduction
- selective fetocide
- septostomy
- termination of pregnancy
What is the survival rate of MCT with TTTS following laser coagulation
Up to 70 %
What was the Eurofetus trial
RCT comparing laser therapy vs amnioreduction for TTTS before 26 weeks.
What were the findings of the eurofetus trial (3)
1) laser group had a higher likehood of Infant survival(of at least one twin) to 28days of life and 6mnths of age.
76% vs 56%
2) laser group has less periventricular leukomalacia
3) median gestational age of delivery laser 33.3 weeks and amnioreduction 29 weeks
How many MCT are affected by twin reversed arterial perfusion sequence
5%
What is TRAP
An acardiac “perfused twin” receives its blood supply from a large arterio-arterial anastamosis from the “pump twin” resulting in absent or rudimentary development of the head, heart and upper limb
What is the mortality rate of the pump twin in TRAPS
> 50%
What is the cause behind mortality of TRAPS
High output congestive heart failure and hydrops
Definitive management on TRAP
Separation of the Cardiovascular circulation by diathermy occlusion of the cord of the acardiac twin
What is a significant twin discordance
20%
How is twin discordance calculated
(EFW larger twin - EFW smaller twin)÷ EFW larger twin x 100
What percentage of monchorionic twins are complicated by selective growth restriction
10-15%
What percentage of MCMA twins have cord entanglement in T3
Up to 100%
What feature is seen on doppler confirming cord entanglement
Galloping sign - two asynchronous heart beats
What is the perinatal loss rate of MCMA twins
10-15%
Incidence of conjoined twins
1: 90,000- 100,000
Overall risk of congenital malformations in twins
600 per 10000 twin births
What congenital anomalies are associated with monozygotic twins (3)
- holoprosencephaly
- neural tube defects
- cloacal extrophy
Risk of cardiac anomalies
1) MCDA
2) MCMA
MCDA: 7%
MCMA: 57%
What percentage of live births are twin pregnancies
3%
What percentage of twins deliver before 37 weeks
50%
What percentage of twins deliver before 32 weeks
10%
What is the risk of neurological abnormality in surviving twin of iufd mcda
26%
What is the risk of second twin death if one twin dies in a monochorionic pregnancy
15%
Incidence of conjoined twins
1:100,000
What percentage of live births are twin
3%
What is the associated perinatal mortality of a twin compared to singleton
3 times higher
What percentage of ivf pregnancies are multiple preg
24%
What percentage of twins in the uk are monochorionic
30%
What percentage of live births are twins
3%