Guideline No. 428: Management of Dichorionic Twin Pregnancies

Objective: To review evidence-based recommendations for the management of dichorionic twin pregnancies. Target Population: Pregnant women with a dichorionic twin pregnancy. Benefits, Harms, and Costs: Implementation of the recommendations in this guideline may improve the management of twin pregnancies and reduce neonatal and maternal morbidity and mortality. Evidence: Published literature was retrieved through searches of PubMed and the Cochrane Library using appropriate controlled vocabulary (e.g., twin, preterm birth). Results were restricted to systematic reviews, randomized controlled trials, controlled clinical trials, and observational studies. There were no date limits, but results were limited to English- or French-language materials. Validation Methods: The content and recommendations were drafted and agreed upon by the principal authors. The Board of the SOGC approved the final draft for publication. The authors rated the quality of evidence and strength of recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. See online Appendix A (Tables A1 for definitions and A2 for interpretations of strong and weak recommendations). Intended Audience: Obstetricians, family physicians, nurses, midwives, maternal–fetal medicine specialists, radiologists, and other health care providers who care for women with twin pregnancies. SUMMARY STATEMENTS: 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). RECOMMENDATIONS: 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).