Multiple pregnancy Flashcards
What are the types of twins?
Dizygotic twins- 2/3- result from fertilisation of different oocytes by different sperm
Monozygotic twins- result from mitotic division of a single zygote into ‘identical twins’, whether they share the same amnion or placenta depends on the time at which division into separate zygotes occurred
What occurs with division at different stages for monozygotic twins?
o Division before day 3- twins with separate placenta and amnions- dichorionic diamniotic
o Division between day 4-8- twins with a shared placenta, but different amnions- monochorionic diamniotic
o Division between day 9-13- very rare and causes twins with shared placenta and amnion-
monochroionic monoamniotic
o Incomplete division- conjoined twins
What is the aetiology of multiple pregnancy?
o Assisted conception
o Genetic factors
o Increasing maternal age
o Parity
• About 20% of all IVF conceptions and 5-10% of clomiphene-assisted conceptions are multiple
• Vomiting may be more marked in early pregnancy- the uterus is also larger for expected from the dates and palpable <12 weeks
What are the maternal complications for multiple pregnancy?
- All obstetric risks are exaggerated in multiple pregnancies- gestational diabetes and pre-eclampsia are particularly more frequent
- Anaemia is common- partly because of a greater increase in blood volume causing dilutional effect and partly because more iron and folic acid are needed
What are the foetal antenatal complications of multiple pregnancy?
• Twins have greater mortality (x6) and long-term handicap (x5)
• Triplets fare even worse- with an x18 increase in handicap
o Preterm delivery
o IUGR
o Monochrorionicity
Miscarriage- 1st trimester death and twin-twin transfusion syndrome
Congenital abnormalities- not more common per baby in dichorionic, but they are in monochorionic pregnancies
What is twin-twin transfusion syndrome?
occurs only in MCDA twins
results from unequal blood distribution through vascular anastomoses of the shared placenta
one twin (the donor) is volume depleted and develops anaemia, IUGR and oligohydramnios
one twin (the recipient) becomes volume overloaded and may develop polycythaemia, cardiac failure and massive polyhydramnios causing massive distension of the uterus (in extremis)
disease is staged according to Quintero in stages 1-5, both twins are at very high risk of in utero death or severely preterm delivery
What is twin anaemia polycythaemia sequence (TAPS)?
occurs where there are marked Hb differences between MC twins, but in the absence of the liquor volume changes characteristic of TTTS
occurring as a consequence of small placental anastomoses, it can follow incomplete laser ablation for TTTS
What is twin reversed arterial perfusion (TRAP)?
rare abnormality of MC twins
an abnormal, often acardiac foetus
is perfused by a normal ‘pump’ twin- therefore is at risk of cardiac failure
What are the other complications of monochorionic pregnancies?
IUGR- particular problem is where the umbilical artery waveform of the smaller twin is very erratic, this may be the result of the superficial artery-artery anastomoses, sudden in utero death occurs in up to 20% and handicap in 8%
Co-twin death- if one of an MC twin pair dies due to TTTS or any other cause- the drop in its blood pressure allows acute transfusion of blood from the other twin, this rapidly leads to hypovolaemia and in 30% of cases, death or neurological damage
• Monoamniotic twins- the cords are always entangled
in utero demise is common, probably because of this and/or sudden acute shunting of blood between the two babies in anastomoses between the close cord insertions
What are the intrapartum complications of multiple pregnancy?
- Malpresentation- of the 1st twin occurs in 20%, this is an indication for C-section
- Foetal distress- common in labour, the 2nd twin delivered has an increased risk of death (x5) after the first has been delivered because of hypoxia, cord prolapse, tetanic uterine contraction or placental abruption, may present as breech
- Postpartum haemorrhage- more common (10%)
What is the antepartum management for all multiples?
iron & folic acid supplements are prescribed and low-dose aspirin is advised if there are other risk factors to prevent pre-eclampsia
• Chronicity is most accurately ascertained in the 1st trimester
o DC twins- dividing membrane is thicker as it meets the placentas (lambda sign)
o MC twins- dividing membrane is thinner and perpendicular to the shared placenta (T sign)
• IUGR is harder to detect in multiple pregnancies- serial USS for growth are routinely performed at 28, 32 and 36 weeks, more often in MC twins
• Delivery at 37 weeks for DC and 36 weeks for uncomplicated MC twins
What is the management for monochorionic twins?
• USS surveillance for MC twins starts by 12 weeks, USS is advised every 2 weeks until 24 weeks and every 2- 3 weeks after that
• TTTS is most commonly diagnosed between 16-24 weeks: laser ablation of the entire placental interface using USS and fetoscope
pregnancies complicated by TTTS after 26 weeks are usually delivered
• IUGR is managed by careful surveillance and iatrogenic preterm delivery occasionally laser ablation or
umbilical cord occlusion are appropriate if at ‘pre-viable’ gestations
survival of both twins in 50% and one twin is 80%
What is the management for high order multiple pregnancy?
- Selective reduction- to a twin pregnancy at 12 weeks should be discussed with women with triplets or higher order pregnancies- this is highly emotive, slightly increases early miscarriage rates, it reduces the chances of preterm birth and therefore cerebral palsy, safest before 14 weeks
- Surveillance according to the chorionicity- delivery by 36 weeks is usually advised
What is the management for foetal abnormalities in multiple pregnancy?
- Before 14 weeks- intracardiac injection of KCL can be used in DC twins, it can be offered up to 32 weeks if late termination of pregnancy is legal
- In MC twins- the cord must be occluded using bipolar diathermy or its insertion ablated as the circulation is shared
What is the mode of delivery in multiple pregnancy?
- If the presenting twin is cephalic- C-section does not improve perinatal outcome, it is only indicated if the 1st twin is breech or transverse lie, with high order multiples or if there have been antepartum complications
- Vaginal delivery when the 1st foetus is cephalic is commonplace, whatever the lie or presentation of the 2nd
