A dichorionic diamniotic (DCDA) twin pregnancy is a type of twin pregnancy where each twin has its own chorionic and amnionic sacs. This type occurs most commonly with dizygotic twins, but may also occur with monozygotic twin pregnancies. This type of pregnancy may have characteristic findings on ultrasound.
DCDA pregnancies account for the majority (~76%) of all twin pregnancies. They account for all dyzgotic pregnancies and ~20% of monozygotic pregnancies.
With a dizygotic pregnancy two ova are independently fertilised by two sperm leading to two zygotes.
With a monozygotic twin pregnancy, a DCDA pregnancy results from seperation of the zygotes at ~1-4 days post fertilisation (morula) stage.
Sonographic assessment of chorionicity is most accurate in the first trimester.
Features supporting a DCDA pregnancy:
- presence of two gestational sacs with a thick echogenic chorion surrounding each embryo
- a thick inter twin membrane
- twin peak sign
- two yolk sacs may be seen (this however does not differentiate a DCDA pregnancy from a monochorionic diamniotic (MCDA) pregnancy)
- when there is no placental fusion, two seperate placental sites may be seen 4
- a finding of two different genders for each twin is a definitive feature for a dizygotic pregnancy which in turn will invariably mean a DCDA pregnancy
If the twins are of the same gender then it is extremely difficult if not impossible to determine if they are monozygotic or dizygotic on ultrasound.
While the complication rate is still much higher with twins than with a singleton pregnancy, a DCDA pregnancy carries the lowest rate of complications amongst twin pregnancies. Such recognised complications include:
- increased risk of intrauterine growth restriction (IUGR)
- placenta-related problems
Ultrasound - obstetric
- ultrasound (introduction)
- obstetric ultrasound
first trimester and early pregnancy
- gestational sac
- yolk sac
- Beta-hCG levels
- ectopic pregnancy
- multiple gestations
- subchorionic hematoma
- failed early pregnancy
- fetal biometry
- fetal morphology assessment
- soft markers
- echogenic fetal bowel
- umbilical artery Doppler assessment
- nuchal translucency
- chorionic villus sampling (CVS) and amniocentesis
- first trimester and early pregnancy
- 1. Trop I. The twin peak sign. Radiology. 2001;220 (1): 68-9. Radiology (full text) - Pubmed citation
- 2. Merz E, Bahlmann F. Ultrasound in obstetrics and gynecology. Thieme Medical Publishers. (2005) ISBN:1588901475. Read it at Google Books - Find it at Amazon
- 3. Kurtz AB, Wapner RJ, Mata J et-al. Twin pregnancies: accuracy of first-trimester abdominal US in predicting chorionicity and amnionicity. Radiology. 1992;185 (3): 759-62. Radiology (abstract) - Pubmed citation
- 4. Hertzberg BS, Kurtz AB, Choi HY et-al. Significance of membrane thickness in the sonographic evaluation of twin gestations. AJR Am J Roentgenol. 1987;148 (1): 151-3. AJR Am J Roentgenol (abstract) - Pubmed citation
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Dichorionic diamniotic twins||✗|
|di-chorionic di-amniotic (DCDA) pregnancy||✗|
|Dichorionic diamniotic pregnancy||✗|
|Dichorionic diamniotic (DCDA) twins||✗|
|Dichorionic diamniotic (DCDA) pregnancy||✗|
|Dichorionic - diamniotic pregnancy||✗|