USMLE Step 2 CK Lecture Notes 2019: Obstetrics/Gynecology (Kaplan Test Prep)

OB TRIAD

Di–Di   Di  or  Mono–Di–Di  Twins

Multiple gestation is a pregnancy in which more than one fetus is present. The
fetuses may arise from one or more zygotes and are usually separate, but may
rarely be conjoined.

Risk Factors.

Mono–Mono–Di    Twins

Diagnosis. Obstetric sonogram demonstration of more than one intrauterine
fetus.

Twin    pregnancy

Gender  same    or  unknown

Two placentas   seen

Twin    pregnancy

Gender  always  same

One placenta    but two sacs

Dizygotic   twins   are most    common. Identifiable    risk    factors include race,

geography,  family  history,    or  ovulation   induction.  Risk    of  twinning    is  up  to

10% with    clomiphene  citrate and up  to  30% with    human   menopausal

gonadotropin.

Monozygotic twins   have    no  identifiable    risk    factors.