NCBI Bookshelf. NICE's original guideline on multiple pregnancy was published in and ated in This document preserves evidence reviews and committee discussions for areas of the guideline that were not ated in Ultrasound is an established tool for dating singleton pregnancies to avoid unnecessary elective preterm delivery, to plan delivery or intervention where appropriate at an appropriate time, and to avoid post- term complications. Twin and triplet pregnancies are at higher risk of preterm delivery than are singleton pregnancies, making accurate dating essential.
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Jan 29, WWE's Bella Twins (Nikki and Brie) are pregnant. Both of them. And they're due just a week and a half apart. The twins, 36, broke the news to People, telling the . The aim of this study was to assess the performance of validated singleton crown-rump length (CRL) formulae in dating twin pregnancies at weeks of gestation. Twin pregnancies are at increased risk of perinatal morbidity and mortality, compared with singletons, mainly as a consequence of both preterm delivery and fetal growth restriction. Accurate dating of twin pregnancies is therefore vital, but there are two particular areas of concern when trying to achieve jankossencontemporary.com by:
By Extra Mustard. By Tim Hackett. Gestational age estimation in twins was not statistically significantly different from singletons when dating was carried out by a formula based on femur length, head circumference and abdominal circumference very low quality evidencebut the same formula systematically underestimated gestational age in triplets by 1 day very low quality evidence.
There was no statistically significant difference in dating by day of oocyte retrieval between twin and singleton pregnancies low quality evidence. Similarly, there was no evidence to suggest that any specific fetal measurement in multiple pregnancies was more effective than another in gestational age estimation.
The majority of the studies appeared to use date of oocyte retrieval to determine the true gestational age. However, the studies were limited, with bias from small sample sizes, operator bias and studies being retrospective. The impact of the use of the timing of oocyte retrieval versus the timing of embryo transfer on dating could not be evaluated from the searches conducted for the guideline no additional searches for evidence relating to singleton pregnancies could be conducted within the timescale for developing the guideline.
With regard to which fetus should be used for estimating gestational age in twin and triplet pregnancies, the GDG was of the view that there was a possibility that in the first half of pregnancy, when gestational age is determined, the smaller twin could be pathologically undergrown in some cases. That would mean that use of the measurements from the smaller fetus could lead to an underestimate of gestational age. No evidence was available for prediction of fetal growth restriction as an outcome and whether use of the smaller fetus in twin pregnancies with impaired growth potential leads to this error in practice.
Evidence was, however, available for growth discordance between twins, that resulted in an average discrepancy of 3. No evidence was available for prediction of other twin complications or congenital anomalies.
Dating twin pregnancies
One study suggested that dating of twin pregnancies was more accurate when the smaller twin, rather than the larger twin, was used very low quality evidence.
However, two other studies showed evidence supporting the use of the average fetal size to determine gestational age in twins and triplets very low quality evidence.
No published health economics evidence was identified and no original health economic modelling was conducted for this review question. This review question focuses on what to measure when the scan is conducted in a women who is found to have a twin or triplet pregnancy; this has no additional resource implications and is, therefore, not relevant for further health economic analysis.
There is a need to determine which fetus should be used as the reference for the dating process in twin and triplet pregnancies. Accurate estimation of gestational age in such pregnancies is important because it forms the basis for predicting, assessing and managing the potential complications of the pregnancy. All outcomes specific in the review protocol were considered critical in terms of informing recommendations for clinical practice. With regard to which fetus to use, the ultrasound measurements of all fetuses will be taken in the pregnancy in any case.
Evidence shows limited differences between smallest, largest and mean measurements to predict gestational age.
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The GDG therefore considered it more appropriate to date the pregnancy using the largest fetus. The review question including its subsidiary questions was not identified as being of high priority for health economic evaluation. The available evidence was limited in quantity and quality.
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No randomised controlled trials RCTs were identified and most of the included studies were retrospective in design, using a variety of different methodologies for example, categorical versus continuous representation of gestational age, smaller and larger twins analysed independently or combined, size of fetus used to date pregnancy, head circumference versus crown-rump length.
The quality of evidence for differences in fetal size in twin and triplet pregnancies versus singleton pregnancies was mainly very low.
The quality of evidence for differences in dating of twin and triplet pregnancies versus singleton pregnancies was also mainly very low, as was the quality of evidence for prediction of growth discordance and accuracy of dating.
The majority of the studies did not report chorionicity or ethnicity. Only one study considered triplets, with the other studies concentrating on twins.
This review question addressed whether there are differences in dating or the size of singleton versus twin or triplet pregnancies that should be taken into account when calculating gestational age in clinical practice.
In view of the limitations of the evidence, the GDG based its recommendation on consensus within the group and highlighted the need for further research in this area. The best interval for performing all three tests together is, therefore, when crown-rump length is between 45 mm and 84 mm at approximately 11 weeks 0 days to 13 weeks 6 days. In practice, it may not be possible to schedule all three tests at the same appointment, and in such circumstances more than one appointment in a short period may be needed.
- Outcome of twin pregnancies - Mortality per live births by plurality - Similarities and differences among TTTS, TAPS, and sIUGR on U/S - Diagnosis and classification of selective FGR - GA and BW characteristics of US singleton twin triplet births - Twin pregnancy nutritional recommendations - Maternal age-related risk common fetal trisomy across pregnancy. Ultrasound is an established tool for dating singleton pregnancies to avoid unnecessary elective preterm delivery, to plan delivery or intervention (where appropriate) at an appropriate time, and to avoid post-term complications. Twin and triplet pregnancies are at higher risk of preterm delivery than are singleton pregnancies, making accurate dating essential. 'Antenatal care' (NICE.
However, if the woman is known in advance to have a twin or triplet pregnancy for example, if such a pregnancy results from IVF treatment it may be possible to plan to schedule all three tests in a single appointment. Evidence suggests that the mean twin measurement best reflects gestational age, both in the first and second trimesterwhether using crown-rump length in the first trimester or head circumference in the second trimester.
The GDG recommends using the larger twin measurement to determine gestational age in the first half of pregnancy because using the mean twin measurement would lead to an underestimate of gestational age if the smaller twin were pathologically undergrown.
Similarly, the largest triplet measurement should be used to date triplet pregnancies. This guideline specifies the care that women with twin and triplet pregnancies should receive that is additional or different from routine antenatal care for women with singleton pregnancies.
Table 5. Note that for many women the twin or triplet pregnancy will be detected only after their routine booking appointment. View in own window. However, the aim in this recommendation is to keep to a minimum the number of scan appointments that women need to attend within a short time, especially if it is already known that a woman has a twin or triplet pregnancy.
Pregnancy risks, clinical management and subsequent outcomes are very different for monochorionic and dichorionic twin pregnancies and monochorionic, dichorionic and trichorionic triplet pregnancies.
Currently, there appears to be considerable variation and uncertainty in the practice of assigning chorionicity for twin and triplet pregnancies, leading to the GDG prioritising this question for review.
Diagnostic accuracy of various methods for determining chorionicity in twin and triplet pregnancies at different gestational ages was sought. What is the optimal method to determine chorionicity in multiple pregnancies?
No existing NICE guidance was identified as being relevant to this review question. Fourteen studies investigating diagnostic accuracy of the following characteristics as determined by an ultrasound scan for determining chorionicity were identified for inclusion: Only two studies included triplets, and one of these included only one triplet pregnancy, meaning that sensitivity, specificity, positive predictive values PPVs and negative predictive values NPVs and likelihood ratio statistics could not be calculated using the triplet data in the study.
Six prospective cohort studies reported findings for using membrane thickness to determine chorionicity in twin pregnancies. Four prospective cohort studies reported on using the number of placental masses and a lambda or T-sign for determining chorionicity in twin pregnancies. One prospective cohort study reported on using the number of membrane layers to determine chorionicity in twin pregnancies.
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One prospective cohort study conducted in the USA reported on using the number of placental sites to determine chorionicity in twin pregnancies. Seven studies reported findings for a mixture of methods for determining chorionicity in twin and triplet pregnancies. Evidence profiles for this question are presented in Tables 4. GRADE summary of findings for scans performed at weeks of gestation.
GRADE summary of findings for scans performed at more than 14 weeks of gestation.
GRADE summary of findings for scans performed before 11 weeks of gestation or over a wide range of gestational ages with no mean age reported. Table 4. Results for twin pregnancies are expressed in terms of detection of monochorionicity. For example, diagnostic accuracy values for the lambda sign are reported as absence of the sign which suggests monochorionicity rather than presence of the sign which suggests dichorionicity. Results for triplet pregnancies are expressed in terms of detection of a monochorionic or dichorionic triplet pregnancy, rather than a trichorionic pregnancy.
Evidence was identified for a variety of methods used to determine chorionicity from ultrasound scans in twin and triplet pregnancies. The sensitivity and specificity of the methods used to determine chorionicity from ultrasound scans is generally high.
The sensitivity for this test was also high. For a mean or median gestational age of more than 14 weeks at the time of scan, results were reported for the use of membrane thickness very low quality evidencethe number of placental sites moderate quality evidence and two different composite methods very low and moderate quality evidence.
The highest sensitivity was reported when membrane thickness was included in the composite method. Some studies reported findings for a gestational age of less than 11 weeks or over a wide range of gestational ages with no mean age reported.
The composite methods showed the strongest likelihood ratios and high sensitivity. The GDG is aware that the evidence presented may be biased due to analysis after the study concluded for patterns that were not specified before the study, particularly in studies that examined individual methods such as membrane thickness.
In these studies, it is not clear how a clinician determining chorionicity on one measure alone such as subjectively thin or thick membrane would not be influenced by other cts of the ultrasound scan such as the number of gestational sacs.
No published health economic analyses were identified and this question was not prioritised for health economic analysis as part of the development of the guideline.
The various measures based on ultrasound scans which were evaluated in terms of diagnostic accuracy could all be obtained from a single scan, and so the costs associated with undertaking individual and composite measures are likely to be similar. Sensitivity is the percentage of pregnancies found to be monochorionic at placental examination that were predicted to be monochorionic at scan true positive. The time at which this separation occurs determines the chorionicity and amnionicity of the pregnancy.
All twin pregnancies have a higher fetal and neonatal mortality with overall rates of fetal mortality being times that of a singleton pregnancy and neonatal mortality 7 times that of single pregnancies. This is primarily due to a much higher incidence of premature labor and all the sequelae thereof. The risk of complications depends on the chorionicity, with the prognosis worst for mono-mono and best for di-di:.
Monochorionic twin pregnancies share the one placenta and are therefore prone to hemodynamic complications such as:. Monoamniotic twin pregnancies share the one amniotic sac and are prone to entangled cordsas well as all the monochorionic complications since you cannot be dichorionic-monoamniotic.
Conjoined twins occur only in monoamniotic pregnancies. The role of ultrasound is crucial adequate in the monitoring of the pregnancy and planning for delivery.
The number of fetuses and their chorionicity and amnionicity must be determined, as well as monitoring for complications and anomalies. Finding the placental sites of umbilical cord insertion are important because marginal and velamentous insertions increase risk 5.
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