Ultrasound in Twin Pregnancies 1: No. 260, June 2011

Outremont QC.
Journal of obstetrics and gynaecology Canada: JOGC = Journal d'obstetrique et gynecologie du Canada: JOGC 10/2011; 115(1):117–118. DOI: 10.1016/j.ijgo.2011.07.001
Source: PubMed


To review the literature with respect to the use of diagnostic ultrasound in the management of twin pregnancies. To make recommendations for the best use of ultrasound in twin pregnancies.
Reduction in perinatal mortality and morbidity and short- and long-term neonatal morbidity in twin pregnancies. Optimization of ultrasound use in twin pregnancies.
Published literature was retrieved through searches of PubMed and the Cochrane Library in 2008 and 2009 using appropriate controlled vocabulary (e.g., twin, ultrasound, cervix, prematurity) and key words (e.g., acardiac, twin, reversed arterial perfusion, twin-to-twin transfusion syndrome, amniotic fluid). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. There were no date restrictions. Studies were restricted to those with available English or French abstracts or text. Searches were updated on a regular basis and incorporated into the guideline to September 2009. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.
The evidence collected was reviewed by the Diagnostic Imaging Committee of the Society of Obstetricians and Gynaecologists of Canada, with input from members of the Maternal Fetal Medicine Committee and the Genetics Committee of the SOGC. The recommendations were made according to the guidelines developed by The Canadian Task Force on Preventive Health Care (Table 1).
The benefit expected from this guideline is facilitation and optimization of the use of ultrasound in twin pregnancy. SUMMARY STATEMENTS: 1. There are insufficient data to make recommendations on repeat anatomical assessments in twin pregnancies. Therefore, a complete anatomical survey at each scan may not be needed following a complete and normal assessment. (III) 2. There are insufficient data to recommend a routine preterm labour surveillance protocol in terms of frequency, timing, and optimal cervical length thresholds. (II-2) 3. Singleton growth curves currently provide the best predictors of adverse outcome in twins and may be used for evaluating growth abnormalities. (III) 4. It is suggested that growth discordance be defined using either a difference (20 mm) in absolute measurement in abdominal circumference or a difference of 20% in ultrasound-derived estimated fetal weight. (II-2) 5. Although there is insufficient evidence to recommend a specific schedule for ultrasound assessment of twin gestation, most experts recommend serial ultrasound assessment every 2 to 3 weeks, starting at 16 weeks of gestation for monochorionic pregnancies and every 3 to 4 weeks, starting from the anatomy scan (18 to 22 weeks) for dichorionic pregnancies. (II-1) 6. Umbilical artery Doppler may be useful in the surveillance of twin gestations when there are complications involving the placental circulation or fetal hemodynamic physiology. (II-2) 7. Although many methods of evaluating the level of amniotic fluid in twins (deepest vertical pocket, single pocket, amniotic fluid index) have been described, there is not enough evidence to suggest that one method is more predictive than the others of adverse pregnancy outcome. (II-3) 8. Referral to an appropriate high-risk pregnancy centre is indicated when complications unique to twins are suspected on ultrasound. (II-2) These complications include: 1. Twin-to-twin transfusion syndrome 2. Monoamniotic twins gestation 3. Conjoined twins 4. Twin reversed arterial perfusion sequence 5. Single fetal death in the second or third trimester 6. Growth discordance in monochorionic twins. Recommendations 1. All patients who are suspected to have a twin pregnancy on first trimester physical examination or who are at risk (e.g., pregnancies resulting from assisted reproductive technologies) should have first trimester ultrasound performed. (II-2A) 2. Every attempt should be made to determine and report amnionicity and chorionicity when a twin pregnancy is identified. (II-2A) 3. Although the accuracy in confirmation of gestational age at the first and second trimester is comparable, dating should be done with first trimester ultrasound. (II-2A) 4. Beyond the first trimester, it is suggested that a combination of parameters rather than a single parameter should be used to confirm gestational age. (II-2C) 5. When twin pregnancy is the result of in vitro fertilization, accurate determination of gestational age should be made from the date of embryo transfer. (II-1A) 6. There is insufficient evidence to make a recommendation of which fetus (when discordant for size) to use to date a twin pregnancy. However, to avoid missing a situation of early intrauterine growth restriction in one twin, most experts agree that the clinician may consider dating pregnancy using the larger fetus. (III-C) 7. In twin pregnancies, aneuploidy screening using nuchal transluscency measurements should be offered. (II-2B) 8. Detailed ultrasound examination to screen for fetal anomalies should be offered, preferably between 18 and 22 weeks' gestation, in all twin pregnancies. (II-2B) 9. When ultrasound is used to screen for preterm birth in a twin gestation, endovaginal ultrasound measurement of the cervical length should be performed. (II-2A) 10. Increased fetal surveillance should be considered when there is either growth restriction diagnosed in one twin or significant growth discordance. (II-2A) 11. Umbilical artery Doppler should not be routinely offered in uncomplicated twin pregnancies. (I-E) 12. For defining oligohydramnios and polyhydramnios, the ultrasonographer should use the deepest vertical pocket in either sac: oligohydramnios when < 2 cm and polyhydramnios when > 8 cm. (II-2B).

Download full-text


Available from: Marie-France Delisle, Apr 14, 2014
  • Source
    • "The Canadian Task Force on Preventive Health Care has made recommendations for the best use of ultrasound in twin pregnancies based on the study by Morin and Lim.16 The authors emphasize the need to adhere to these recommendations to reduce such preventable maladies. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Conjoined twins are a very rare entity. It is associated with poor survival rate in the presence of vital organ sharing. The entity can be diagnosed as early as the first trimester. A conjoined twin diagnosed late in labor is a malady with high perinatal mortality and maternal morbidity. We present one such case of xiphopagus twins. The management of a case diagnosed late in labor can be very challenging. Such obstetric challenges can be avoided by a meticulous early scan with a high index of suspicion, especially in the absence of separating membrane while scanning multiple pregnancies.
    Full-text · Article · Feb 2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: The widespread use of assisted reproductive technologies has led to an increase in the prevalence of monozygotic twins. Twinning after blastocyst transfer results in monochorionic placentation; a form of placentation that is associated with higher risks of mortality and morbidity. This study describes complication rates of monochorionic diamniotic (MCDA) twin pregnancies and examines whether they differ between spontaneous and assisted conceptions. A five-year retrospective review of 294 MCDA twin pregnancies that had no evidence of structural abnormality on ultrasound at 12 weeks' gestation. Outcomes of spontaneous and assisted conceptions Day 3 (D3) cleavage stage embryo or Day 5 (D5) blastocyst transfer) pregnancies were compared. Two hundred and eighteen (74.1%) MCDA twin pregnancies were conceived spontaneously, whilst 14 (4.8%) resulted from D3 cleavage stage embryo and 62 (21.1%) resulted from D5 blastocyst transfer. Fetal and whole pregnancy loss rates were high, affecting 11.4% and 8.8% of cases, respectively. 16.2% of pregnancies were delivered <32 weeks' and 66% <37 weeks' gestation. 36.2% of infants were small for gestational age and selective intrauterine growth restriction (IUGR) affected 7.5% of pregnancies. There was no significant difference in the prevalence of complications between spontaneous and assisted conceptions. Assisted conception with either D3 cleavage stage embryo or D5 blastocyst transfer does not increase the risk of complication in a MCDA twin pregnancy. Mortality in monochorionic twins remains high despite early recognition and heightened surveillance throughout pregnancy. Information describing the risks of monochorionic twinning and of subsequent complications may be of value to women undergoing assisted conception.
    No preview · Article · Jul 2013 · Australian and New Zealand Journal of Obstetrics and Gynaecology
  • [Show abstract] [Hide abstract]
    ABSTRACT: The objective of this review is to assess the evidence that supports the use of ultrasound in twin pregnancies. Although many of the indications for obstetric ultrasound are the same in both singleton and multiple gestations, there are special considerations as well as unique conditions in twins that require additional imaging studies. The reasons for ultrasound in twins include pregnancy dating, determination of chorionicity, nuchal translucency assessment, anatomical survey, placental evaluation, cervical length assessment, routine fetal growth, and serial surveillance of pregnancies complicated by anomalies, cervical shortening, fetal growth disturbances, and amniotic fluid abnormalities. Twins with monochorionic placentation require heightened scrutiny for monoamnionicity, conjoined twins, twin reversed arterial perfusion (TRAP) syndrome, twin-twin transfusion syndrome, unequal placental sharing with discordant twin growth or selective intrauterine fetal growth restriction (IUGR), twin anemia-polycythemia sequence (TAPS), and single fetal demise. Ultrasound is essential for the detection and management of conditions that can complicate dichorionic and monochorionic twin pregnancies.
    No preview · Article · Oct 2013 · Seminars in perinatology
Show more