Multiple pregnancy Flashcards
What are the types of multiple pregnancy?
Dizygotic twins and monozygotic twins
Are dizygotic or monozygotic twins more common?
Dizygotic twins (2/3rds of all multiple pregnancies)
What are dizygotic twins?
Twins that result from fertilisation of different oocytes by different sperm. (unidentical)
What are monozygotic twins?
Twins that result from mitotic division of a single zygote into ‘identical’ twins.
Do monozygotic twins always share the same amnion or placenta?
No, it depends on the time at which division into separate zygotes occurred.
What are dichorionic diamniotic (DCDA) twins?
Twins with separate placentas and amnions
Are DCDA twins more common than MCDA (shared placenta, separate amnions)?
No, MCDA make up 70% of multiple pregnancies
What are the risk factors for multiple pregnancies?
Assisted conception, genetic factors and increasing maternal age and parity are the most important factors, largely affects DZ twinning.
What are the clinical features of multiple pregnancy?
Vomiting may be more marked in early pregnancy. The uterus is larger than expected from the dates and palpable before 12 weeks.
What are the maternal antepartum complications of multiple pregnancy?
Gestational diabetes, PE, anaemia (due to dilution effect and partly because more iron and folic acid are needed)
What are the fetal antepartum complications of multiple pregnancy?
Greater mortality (six fold) and long-term handicap (five fold); preterm delivery; IUGR; congenital abnormalities
What are the complications of monochorionicity?
Largely from shared blood supply of single placenta: twin-twin transfusion syndrome; IUGR; co-twin death.
What is twin-twin transfusion syndrome (TTTS)?
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. The other ‘recipient’ twin gets volume overloaded and may develop polycythaemia, cardiac failure and massive polyhydramnios.
What are the risks of TTTS?
Both twins are at a very high risk of in utero death or severely preterm delivery. Survival of both twins is only 50%.
What is co-twin death?
If one of an MC twin pari dies, either due to TTTS or any other cause, the drop in its blood pressure allows acute transfusion of blood from one to the other one, which leads to raid hypovolaemia and , in about 30% of cases death
What are the intrapartum complications of multiple pregnancy?
Malpresentation of the first twins; fetal distress in labour; PPH
Is the second twin at more risk than the first one?
Yes (five fold increased risk of death), due to hypoxia, cord prolapse, tetanic uterine contraction (>90s) or placental abruption.
How can chorionicity be determined on US?
In first trimester, in dichorionic twins, the dividing membrane is thicker as it meets the placenta and in monochorionic twins the dividing membrane is thin and perpendicular to the shared placenta.
What is the Lambda and the T sign in chorionicity?
Lambda sign - thick diving membrane, dichorionic twins
T sign - thin dividing membrane, monochorionic twins
When and how is TTTS most commonly diagnosed?
Between 16 and 22 weeks, either by careful US including for tricuspid regurgitation or polyhydramnios
How do you treat TTTS?
Expect where the disease is very mild, laser photocoagulation of the placental anastomoses in a fetal medicine centre, using US and fetoscopy
How are multiple pregnancies delivered?
Increasingly using C section, even for uncomplicated twins due to increased risk to second twin.
When are twins induced?
37 weeks with DCDA twins
36 weeks with MCDA twins
32+0 and 33+6 weeks with MCMA twins
What analgesia is used in twins?
Epidural is not mandatory but is helpful if difficulty is encountered with the second twin.
Do contractions alter after the first twin?
They are often diminished after the first twin, but usually return within a few minutes, oxytocin can be started if not
Is the second twin easier to deliver than the first.
Usually, yes
