• Français

Twins, triplets, multiple pregnancy

Complications de grossesse chez la mère


Types of twins:

Fraternal twins (dizygotic twins)

  • May be the same sex or different
  • Do not share the same placenta

Identical twins (monozygotic) 

  • Are the same sex
  • Can share the same placenta, but have their own amniotic sac:
    • This type of twin (monochorionic-diamniotic) is at risk of twin-to-twin transfusion syndrome.
  • Can sometimes share the same amniotic sac:
    • This type of twin (monochorionic-monoamniotic) is at risk of having cord entanglement.

Main complications of multiple pregnancies 

  • Prematurity: The majority of uncomplicated twin pregnancies are delivered at 36 weeks
  • Intrauterine growth restriction
  • Preeclampsia
  • Gestational diabetes
  • Anemia
  • Caesarean section: 50% of women will have to have a caesarean section because the baby is not in a good position for delivery (for example, the baby is positioned to come out bottom first (breech)).
  • Complications related to monozygotic pregnancies (identical twins)
  • Increased risk of birth defects such as heart defects.
  • Twin-to-twin transfusion syndrome: Since twins share the same placenta, blood vessel connections in the placenta allow blood to be exchanged from one twin to the other. Sometimes, an imbalance makes this exchange unidirectional, which means that one fetus gets more blood than the other. In this case, one of the fetuses receives too much blood and can develop heart failure and the other receives too little blood and can become anemic, suffer from renal failure, and have severe intrauterine growth restriction. When not treated, twin-to-twin transfusion syndrome can lead to the death of both fetuses.
  • Cord entanglement: In fetuses that share the same amniotic sac, the cords can get tangled and accidentally interrupt blood flow, causing the death of one of the fetuses.

Support and follow-up care

As soon as the diagnosis of a twin pregnancy is made, it is necessary to quickly specify the type in order to establish a targeted monitoring plan.

For dizygotic twins, obstetrical ultrasounds every 3 to 4 weeks starting from the 16th week are planned to detect any growth restrictions.

For monozygotic twins, obstetrical ultrasounds every 2 weeks starting from the 16th week are planned to screen for twin-to-twin transfusion syndrome. If this diagnosis is made, doctors will consider laser treatment, which usually helps cure this disorder.

In addition, for monochorionic-monoamniotic twins, close monitoring of the 2 fetuses is performed daily from the 24th or 26th week of pregnancy.

Resources and useful links

Page by

Josée Normandeau, inf. clinicienne et Dre Lucie Morin

About this page
Updated on 1/25/2021
Created on 12/19/2017
Alert or send a suggestion

Every dollar counts!

Thank you for your generosity.

It is thanks to donors such as you that we are able to accelerate research discoveries, to heal more children every year and to continue to offer world-class care.

It is also possible to give by mail or by calling toll-free

1-888-235-DONS (3667)

Contact Us

514 345-4931


© 2006-2014 CHU Sainte-Justine.
All rights reserved. 
Terms of Use,  Confidentiality,  Security


All information contained within the CHU Sainte-Justine site should not be used as a substitute for the advice of a duly qualified and authorized medical practitioner or any other health professional. The information provided on this site is intended for educational and informational purposes only.

Consult your physician if you feel ill or call 911 for any medical emergency.

CHU Sainte-Justine