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Multiple gestation

What's new

The Royal College of Obstetricians and Gynaecologists (RCOG) has published a partial update on the management of monochorionic twin pregnancy, including new recommendations on the use of cell-free fetal DNA (cffDNA) testing and the screening and management of twin-to-twin transfusion syndrome (TTTS). cffDNA testing is recommended in twin pregnancies, including monochorionic twins, based on the results of the first-trimester combined test for major autosomal trisomies. For TTTS, increasing ultrasound monitoring frequency to at least weekly is recommended when differences in amniotic fluid levels are observed during the second or third trimester. Evidence supports performing fetoscopic laser ablation using a serial, sequential technique followed by equatorial laser dichorionization (the SOLOMON technique). .

Background

Overview

Definition
Multiple gestation is a pregnancy involving two or more fetuses, classified by zygosity (monozygotic, dizygotic, or higher order), chorionicity (monochorionic, dichorionic, or higher order), and amnionicity (monoamniotic, diamniotic, or higher order).
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Pathophysiology
The pathophysiology of multiple gestation include either fertilization of multiple eggs by separate sperms leading to dizygotic (fraternal) twins or splitting of a single fertilized egg into two or more embryos leading to monozygotic (identical) twins.
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Epidemiology
The incidence of multiple gestation in the US is estimated at 10-30 multiple births per 1,000 live births.
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Risk factors
Risk factors for multiple gestation include older maternal age, nulliparity, assisted reproductive techniques (IVF), ovarian stimulation, and a history of multiple gestations.
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Disease course
The clinical course of multiple gestation is characterized by increased risks and complications. These include preterm labor and preterm birth, slower fetal growth, smaller birth size, and a higher risk of iron-deficiency anemia. There are also specific circumstances, such as selective intrauterine growth restriction and twin-twin transfusion syndrome, that can occur in multiple gestations.
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Prognosis and risk of recurrence
The prognosis of multiple gestation can vary, but there is generally a higher risk of neonatal and maternal complications compared to singleton pregnancies.
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Guidelines

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 International Society of Ultrasound in Obstetrics and Gynecology (ISUOG 2025), the Royal College of Obstetricians and Gynaecologists (RCOG 2025), the Society of Obstetricians and Gynaecologists of Canada (SOGC 2023,2022,2017,2013), the American College of Medical Genetics (ACMG 2022), ...
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