Multiple Pregnancy

Question 1

What is a multiple pregnancy?

Answer 1

Multiple pregnancy refers to a pregnancy with more than one fetus. The incidence of multiple pregnancies increased with the development of fertility treatment.

Question 2

Briefly differentiate between:

• Monozygotic
• Dizygotic

Answer 2

Monozygotic: identical twins (from a single zygote).

Dizygotic: non-identical (from two different zygotes).

Question 3

Briefly differentiate betwen:

• Monoamniotic
• Diamniotic

Answer 3

Monoamniotic: single amniotic sac.

Diamniotic: two separate amniotic sacs.

Question 4

Briefly differentiate between:

• Monochorionic
• Dichorionic

Answer 4

Monochorionic: share a single placenta.

Dichorionic: two separate placentas.

Question 5

What is the best outcome for multiple pregnancies?

Answer 5

The best outcomes are with diamniotic, dichorionic twin pregnancies, as each fetus has their own nutrient supply.

Question 6

When are multiple pregnancies diagnosed?

Answer 6

Multiple pregnancy is usually diagnosed on the booking ultrasound scan.

Ultrasound is also used to determine the:

• Gestational age
• Number of placentas (chorionicity) and amniotic sacs (amnionicity)
• Risk of Down’s syndrome (as part of the combined test)

Question 7

When determining the type of twins using an ultrasound scan, what do the following terms mean…?

• Dichorionic diamniotic twins
• Monochorionic diamniotic twins
• Monochorionic monoamniotic twins

Answer 7

Dichorionic diamniotic twins have a membrane between the twins, with a lambda sign or twin peak sign.

Monochorionic diamniotic twins have a membrane between the twins, with a T sign.

Monochorionic monoamniotic twins have no membrane separating the twins.

Question 8

Briefly describe the lambda or twin peak sign

Answer 8

The lambda sign, or twin peak sign, refers to a triangular appearance where the membrane between the twins meets the chorion, as the chorion blends partially into the membrane. This indicates a dichorionic twin pregnancy (separate placentas).

Question 9

Briefly describe the T sign

Answer 9

The T sign refers to where the membrane between the twins abruptly meets the chorion, giving a T appearance. This indicates a monochorionic twin pregnancy (single placenta).

Question 10

What are the complications of multiple pregnancies to the mother?

Answer 10

Risks to the mother:

• Anaemia
• Polyhydramnios
• Hypertension
• Malpresentation
• Spontaneous preterm birth
• Instrumental delivery or caesarean
• Postpartum haemorrhage

Question 11

What are the complciations of multiple pregnancies to the fetuses and neonates?

Answer 11

Risks to the fetuses and neonates:

• Miscarriage
• Stillbirth
• Fetal growth restriction
• Prematurity
• Twin-twin transfusion syndrome
• Twin anaemia polycythaemia sequence
• Congenital abnormalities

Question 12

Briefly describe twin-twin transfusion syndrome

Answer 12

Twin-twin transfusion syndrome occurs when the fetuses share a placenta. It is called feto-fetal transfusion syndrome in pregnancies with more than two fetuses.

When there is a connection between the blood supplies of the two fetuses, one fetus (the recipient) may receive the majority of the blood from the placenta, while the other fetus (the donor) is starved of blood. The recipient gets the majority of the blood, and can become fluid overloaded, with heart failure and polyhydramnios. The donor has growth restriction, anaemia and oligohydramnios. There will be a discrepancy between the size of the fetuses.

Women with twin-twin transfusion syndrome need to be referred to a tertiary specialist fetal medicine centre. In severe cases, laser treatment may be used to destroy the connection between the two blood supplies.

Question 13

Briefly describe twin anaemia polycythaemia sequence

Answer 13

Twin anaemia polycythaemia sequence is similar to twin-twin transfusion syndrome, but less acute. One twin becomes anaemic whilst the other develops polycythaemia (raised haemoglobin).

Question 14

What additional monitoring is required for anaemia in multiple pregnancies?

Answer 14

Women with multiple pregnancies require additional monitoring for anaemia, with a full blood count at:

• Booking clinic
• 20 weeks gestation
• 28 weeks gestation

Question 15

What additional USS monitoring is required in multiple pregnancy?

Answer 15

Additional ultrasound scans are required in multiple pregnancy to monitor for fetal growth restriction, unequal growth and twin-twin transfusion syndrome:

• 2 weekly scans from 16 weeks for monochorionic twins
• 4 weekly scans from 20 weeks for dichorionic twins

Question 16

When is planned birth offered for in the following multiple pregnancies…?

• Uncomplicated monochorionic monoamniotic twin
• Uncomplicated monochorionic diamniotic twins
• Uncomplicated dichorionic diamniotic twins
• Triplets

Answer 16

Planned birth is offered between:

• 32 and 33 + 6 weeks for uncomplicated monochorionic monoamniotic twins
• 36 and 36 + 6 weeks for uncomplicated monochorionic diamniotic twins
• 37 and 37 + 6 weeks for uncomplicated dichorionic diamniotic twins
• Before 35 + 6 weeks for triplets

Question 17

Briefly describe the delivery for monoamniotic and diamniotic twins

Answer 17

Monoamniotic twins require elective caesarean section at between 32 and 33 + 6 weeks.

Diamniotic twins (aim to deliver between 37 and 37 + 6 weeks):

• Vaginal delivery is possible when the first baby has a cephalic presentation (head first)
• Caesarean section may be required for the second baby after successful birth of the first baby
• Elective caesarean is advised when the presenting twin is not cephalic presentation