Benefits, Harms, and Costs
- 1.Although the current evidence suggests the size of the smaller twin would be a more accurate indicator of gestational age in the first trimester, more data is needed to achieve consensus to justify a change in practice. Therefore, the current practice of measuring the larger twin to determine gestational age should continue (moderate).
- 2.Progesterone may reduce the risk of preterm birth in women with a twin pregnancy and a short cervix (moderate).
- 3.There is insufficient evidence to recommend the use of a cervical pessary in women with a twin pregnancy and a short cervix (moderate).
- 4.Informed consent for the mode of delivery for twins should include a discussion of vaginal, cesarean, and combined delivery (high).
- 5.Planned vaginal delivery carries no increased risk compared with planned cesarean delivery (high).
- 6.Internal podalic version and breech extraction is associated with a shorter delivery interval between the first and second twin and may reduce the likelihood of a combined delivery (low).
- 7.There is insufficient evidence to support either vaginal or cesarean delivery as a safer option for women delivering dichorionic twins at a very preterm gestation (or estimated fetal weight <1500 g) (low).
- 8.There is insufficient evidence to support either vaginal or cesarean delivery as a safer option for women delivering dichorionic twins with significant (>25%) growth discordance (low).
- 9.For women with a twin pregnancy and a previous cesarean birth, trial of labour after cesarean (TOLAC) is a safe alternative to elective repeat cesarean delivery (low).
- 1.Chorionicity must be accurately determined and documented during sonographic assessment of all twin pregnancies, preferably at 110–136 weeks gestation (strong, high).
- 2.When a twin pregnancy is conceived through in vitro fertilization, the conception date should be used to determine gestational age (strong, moderate).
- 3.When using sonographic fetal biometry to date a twin pregnancy in the second trimester, the larger biometric estimate should be used (conditional, moderate).
- 4.Antenatal labelling of twins according to their lateral or vertical orientation, rather than their proximity to the cervix, is recommended. In laterally oriented twins, the twin on the maternal right should be labelled as twin A. Twins should be assigned labels at the first sonographic examination, including other discriminating sonographic features that can help with the accuracy of labelling, and the labels should be maintained for all subsequent scans (strong, moderate).
- 5.In uncomplicated dichorionic twin pregnancies, fetal growth should be monitored with scans every 3–4 weeks, starting at about 24 weeks gestation (conditional, low).
- 6.When using sonographic biometry to assess growth velocity, consider using twin-specific growth charts (strong, moderate).
- 7.In women with twin pregnancies, cervical length should be measured (ideally transvaginally) at the anatomy scan and, if possible, once again before 24 weeks, as cervical length is a good predictor of the risk of preterm birth (strong, moderate).
- 8.Bed rest or restriction of activity should not be advised for women with twin pregnancies, whether or not they have risk factors for preterm birth (strong, moderate).
- 9.Cervical cerclage in asymptomatic women with twin pregnancies may be considered when cervical length is ≤15 mm (conditional, moderate) and is recommended with cervical dilation ≥1 cm before 24 weeks gestation (strong, moderate).
- 10.Women with an uncomplicated dichorionic twin pregnancy should be offered elective delivery at 37–38 weeks gestation (strong, moderate).
- 11.Vaginal delivery should be offered when the first twin is presenting cephalic and is not significantly smaller than the second twin, and when a care provider skilled in managing labour and delivery of a second twin with a non-cephalic presentation is available, regardless of the presentation of the second twin, (strong, high).
- 12.For delivery of the second twin, internal podalic version with breech extraction is recommended if the second twin has a non-cephalic presentation (strong, high).
Abbreviations:ART (assisted reproductive technology), CRL (crown–rump length), CVS (chorionic villus sampling), EFW (estimated fetal weight), FGR (fetal growth restriction), IPV (internal podalic version), RCT (randomized controlled trial), TOLAC (trial of labour after cesarean)
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This document reflects emerging clinical and scientific advances as of the publication date and is subject to change. The information is not meant to dictate an exclusive course of treatment or procedure. Institutions are free to amend the recommendations. The SOGC suggests, however, that they adequately document any such amendments.
Informed consent: Everyone has the right and responsibility to make informed decisions about their care, together with their health care providers. To facilitate this, the SOGC recommends that health care providers provide patients with information and support that is evidence-based, culturally appropriate, and personalized.
Language and inclusivity: The SOGC recognizes the importance of being fully inclusive and when context is appropriate, gender-neutral language will be used. In other circumstances, we continue to use gendered language because of our mission to advance women’s health. The SOGC recognizes and respects the rights of all people for whom the information in this document may apply, including but not limited to transgender, non-binary, and intersex people. The SOGC encourages health care providers to engage in respectful conversation with their patients about their gender identity and preferred gender pronouns and to apply these guidelines in a way that is sensitive to each person’s needs.