Screening for chromosomal disorders: you can avail of the NIPT Panorama test from 9 weeks in a twin pregnancy if you wish to rule out Down syndrome, Edwards syndrome and Patau’s syndrome. The test can also tell if your twins are fraternal or paternal! For more information contact the Fetal Medicine Unit 01 872 6572.
The Rotunda Hospital Dublin
Monochorionic Multiple Birth Service
Congratulations, you are expecting twins!
Your twins have been identified as monozygous (identical) and share a placenta, also known as a ‘Monochorionic’ (MC) twin pregnancy. Most women with MC pregnancies deliver healthy babies, however there is a higher risk of some complications.
For this reason your antenatal care will occur in a dedicated Monochorionic Multiple Birth Clinic in the Fetal Assessment Unit at the Rotunda Hospital. The delivery of your babies is recommended in hospital.
Some information about your pregnancy and the conditions we are screening for:
You will have ultrasounds every 2 weeks from 16 weeks gestation until birth. This involves measuring your twins’ size (estimated fetal weight), the level of amniotic fluid volume in each sac, the pattern of flow in the umbilical artery of each twin, and identifying normal bladders in both. This is to screen for the following complications:
a. Fetal growth restriction or growth discordance. This is where one baby is very small and there is a difference in their estimated weights (occurs in approximately 1 in 5 MC twins)
b. Twin-twin transfusion syndrome (TTTS) (occurs in 10-15%) and is due to an imbalance of blood flow from one twin to the other. If suspected, your team will discuss further management which sometimes involves fetal intervention with a laser.
c. Twin-anaemia Polycythaemia Sequence (TAPS) (occurs in 5-13%), is due to smaller connecting vessels than in TTTS; requires close monitoring and if severe, may require an early delivery at around 32 weeks gestation.
d. Rare complications such as TRAP sequence, conjoined twins or congenital abnormalities in one or both twins. If these are identified your team will advise on your subsequent care.
You will have a standard anatomy sonogram at 20-22 weeks’ gestation to screen for fetal abnormalities. This is no different to singleton pregnancies.
In some circumstances, for example if any of the above complications arise, a fetal echocardiogram is arranged between 22-24 weeks.
While uncommon, if one twin’s heart stops beating in the womb it can lead to death or neurodevelopmental consequences in the surviving twin in up to 1/3 cases. If this occurs you will require closer monitoring, and depending on the timing of the demise, a fetal MRI for the surviving twin may be arranged in due course. Mothers expecting twins are at increased risk of developing pre-eclampsia and gestational hypertension, and your team will discuss whether you may benefit from taking aspirin. There is also a higher risk of developing anaemia and gestational diabetes. There is also an increased risk of postpartum haemorrhage and medications such as oxytocin will be advised after birth to prevent this.
The exact timing of birth in a multiple pregnancy will depend on your individual circumstances
60% of mothers expecting twins will deliver before 37 weeks, and 1/5 mothers expecting MC twins will require delivery < 32 weeks’ gestation. If you develop any of the complications listed above you may also require a planned early delivery, the timing of which will depend on the individual circumstances.
For uncomplicated MC twins, delivery is recommended at 36 weeks’ gestation. This may involve an induction of labour.
Pregnancies with MC twins continuing beyond 37 weeks have an increased risk of fetal death of 1.5%, hence the recommendation for earlier delivery.
If the first twin is presenting head first (cephalic), you may have a trial of labour, as this is safe. The position of the second twin can change after the first baby is born and does not influence the delivery.
If you suspect labour or membrane rupture, present as soon as possible to the hospital
If labour is confirmed, an early epidural is recommended as this can be helpful if you go on to require a cesarean section or your babies require an assisted delivery.
After your first baby is born, the team will check the position of the second baby by examining your abdomen and sometimes performing an ultrasound scan. Usually the second twin is delivered within 30 minutes of the first twin being born.
There is a 4% risk of the second twin requiring delivery by cesarean section.
A cesarean section will be advised if the first twin is non-cephalic (for example breech or transverse) or if labour begins very early, for example <32 weeks, however each case is managed individually.
If delivery is planned <37 weeks your team will discuss the role of corticosteroids for fetal lung maturity depending on the timing and the mode of delivery.
Monochorionic Monoamniotic (MCMA) – This means both babies share a placenta and are within the same sac. This is a rare type of twin pregnancy that requires close monitoring and earlier delivery 32-34 weeks. Sometimes a hospital stay is required for a duration of the pregnancy.