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Multiple gestation

Key sources
The following summarized guidelines for the evaluation and management of multiple gestation are prepared by our editorial team based on guidelines from the Society of Obstetricians and Gynaecologists of Canada (SOGC 2023; 2022; 2017; 2013), the American College of Medical Genetics (ACMG 2022), the American College of Obstetricians and Gynecologists (ACOG 2021; 2017), the International Federation of Gynecology and Obstetrics (FIGO 2021), the Royal College of Obstetricians and Gynaecologists (RCOG 2016), and the Society for Maternal-Fetal Medicine (SMFM 2013).


1.Screening and diagnosis

Diagnosis of twin pregnancy: obtain a first-trimester ultrasound in all patients suspected to have or being at risk (such as pregnancies resulting from ART) of having a twin pregnancy on first-trimester physical examination.
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  • Determination of gestational age

  • Determination of chorionicity and amnionicity

2.Classification and risk stratification

Maternal and perinatal risks
As per ACOG 2017 guidelines:
Recognize that multifetal pregnancies increase maternal and perinatal morbidity and mortality. Recognize that higher-order multifetal pregnancies present higher risks than twin pregnancies.
Recognize the medical risks of multifetal pregnancy, the potential medical benefits of multifetal pregnancy reduction, and the complex ethical issues inherent in decisions regarding multifetal pregnancy reduction. Be prepared to respond in a professional and ethical manner to patients requesting or declining to receive information or intervention, or both.

3.Diagnostic investigations

Screening for chromosomal abnormalities, noninvasive testing, SOGC: consider obtaining aneuploidy screening with either combined prenatal serum screening (first-trimester screening or integrated prenatal screening as available) or cell-free fetal DNA analysis of maternal blood in monochorionic pregnancies.

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  • Screening for chromosomal abnormalities (invasive testing)

  • Screening for structural abnormalities

  • Evaluation for discordant abnormalities

  • Monitoring for selective intrauterine growth restriction

  • Monitoring for twin-twin transfusion syndrome

  • Antenatal fetal monitoring

4.Nonpharmacologic interventions

Bed rest: as per SOGC 2022 guidelines, do not advise bed rest or restriction of activity in patients with twin pregnancies, either in the presence or absence of risk factors for preterm birth.

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  • Cervical pessary

5.Therapeutic procedures

Cervical cerclage: as per SOGC 2022 guidelines, consider performing cervical cerclage in asymptomatic patients with twin pregnancies when cervical length is ≤ 15 mm.
perform cervical cerclage when cervical dilation is ≥ 1 cm before 24 weeks gestation.

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  • Selective reduction

  • Management of delivery (monochorionic twins)

  • Management of delivery (dichorionic twins)

6.Specific circumstances

Patients with selective intrauterine growth restriction, diagnosis
Base the definition of fetal growth restriction on a combination of measures of fetal size percentile and Doppler abnormalities.
Take into consideration intertwin size discordance when diagnosing fetal growth restriction in twin gestations, especially in the case of monochorionic placentation.
Consider using twin-specific charts for the assessment of fetal growth in twin gestations to avoid overdiagnosis of fetal growth restriction in this population.

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  • Patients with selective intrauterine growth restriction (management)

  • Patients with twin-twin transfusion syndrome (diagnosis)

  • Patients with twin-twin transfusion syndrome (evaluation)

  • Patients with twin-twin transfusion syndrome (management)

  • Patients with single fetal demise

  • Patients with conjoined twins

7.Patient education

General counseling: as per ACOG 2017 guidelines, provide nondirective counseling in all patients with higher-order multifetal pregnancies and include a discussion of the risks unique to multifetal pregnancy as well as the option to continue or reduce the pregnancy. Consider including maternal-fetal medicine specialists, neonatologists, mental health professionals, child development specialists, support groups, and clinicians with procedural expertise in multifetal pregnancy reduction for providing such counseling.
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8.Preventative measures

Primary prevention: recognize that fertility treatments have contributed significantly to the increase in multifetal pregnancies. Consider implementing primary prevention strategies in the treatment for infertility to limit multifetal pregnancies, especially higher-order multifetal pregnancies, to minimize the need for multifetal pregnancy reduction.

9.Follow-up and surveillance

Indications for referral: refer to, or at least consult with, a regional maternal-fetal medicine program or fetal therapy center to explore all management options for patients with monochorionic twin complications, including:
discordance for an anomaly
selective fetal growth restriction
twin anemia-polycythemia sequence
twin reversed arterial perfusion sequence
single intrauterine demise

10.Quality improvement

Ultrasound operator requirements: train all sonographers undertaking routine ultrasound during pregnancy to establish chorionicity and the correct labeling of twins.
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