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Diagnostic ultrasound ( PDFDrive )

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A

B

C

D

Dichorionic

Diamniotic

Monochorionic

Diamniotic

E

Monochorionic

Monoamniotic

Monochorionic

Monoamniotic

Conjoined

FIG. 32.3 First-Trimester Twins. (A)

Dichorionic diamniotic twins. Two separate

gestational sacs, each with embryo and yolk

sac. Note the thin amnion separated from the

chorion in each sac. (B) Monochorionic diamniotic

twins. Single gestational sac with two

yolk sacs and two embryos (only one is shown).

(C) Monochorionic monoamniotic twins. Single

gestational sac with two separate embryos and

a single surrounding amnion (white arrowhead).

(D) Monochorionic monoamniotic conjoined

twins. Single gestational sac with a single

amnion (white arrowhead), and a single large

embryo that contains two heart beats. See

also Video 32.2. (E) Corresponding line diagram

of irst-trimester pregnancies. Blue, Embryo;

brown, amnion; green, chorion; small black,

yolk sac.

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