Class 13: Multiples Flashcards
type of twinning that is fertilized by 1 ovum & 1 sperm, then splits into 2
monozygotic/identical twins
percentage of twinning that makes up monozygotic twins?
30%
are monozygotic twins hereditary?
no – random
monozygotic twins are always the ___ sex & ____ genetic make up
same sex; identical genetic make up
type of twinning that is fertilized by 2 ovum & 2 sperm
dizygotic/fraternal twins
percentage of twins that make up dizygotic twins
70%
dizygotic twins are always the same sex. T/F?
false
dizygotic twins have ___ genetic make up
different
dizygotic twins always have separate placentas. T/F?
true
race with higher incidence of twinning?
black
race with the lowest incidence of twinning?
asian
age that has a higher incidence of twinning?
older maternal age – 35-39 yo
what type of twin is hereditary?
dizygotic twins
does the maternal or paternal side carry the genes for twinning?
maternal
what type of infertility drugs increases the chance for twinning?
pergonal & clomid
2 layers of placental membranes
- chorion
- amnion
list the types of placentas & membranes
- dichorionic diamniotic
- monochorionic diamniotic
- monochorionic monoamniotic
how many placentas & yolk sacs are in a di-di pregnancy?
2 placentas, 2 yolk sacs
how many placentas & yolk sacs are in a mo-di pregnancy?
1 placentas & 2 yolk sac
how many placentas & yolk sacs are in a mo-mo pregnancy?
1 placenta & 1 yolk sac
what type of placentation can dizygotic twins have?
only dichorionic diamniotic
what type of placentation can monozygotic twins have?
can have all 3 types depending on when division occurred
monozygotic twins must be separated between ____ days after conception for them to have dichorionic diamniotic placentation
0-4 days
monozygotic twins must be separated between ____ days after conception for them to have monochorionic diamniotic placentation
4-8 days
monozygotic twins must be separated between ____ days after conception for them to have monochorionic monoamniotic placentation
8-13 days
incomplete separation occurs if monozygotic twins haven’t separated after ____ days after conception. this is also called ____
13 days; conjoined twinning
which type of placentation exhibits a twin peak/lambda sign?
dichorionic diamniotic
which type of placentation exhibits a T-sign?
monochorionic diamniotic
which fetus would you label “fetus A” on U/S?
the presenting fetus (closest to cervix)
4 types of twin abnormalities?
- vanishing twin syndrome
- fetus papyraceus
- conjoined twinning
- fetus in fetu
what is vanishing twin syndrome?
seeing twin gestation early in pregnancy but only having a singleton at birth
what can be the etiology for vanishing twin syndrome?
one gestation was an anembryonic or nonviable pregnancy & was able to be reabsorbed
US appearance of vanishing twin syndrome
- GS smaller than other according to LMP
- GS with irregular borders
- GS crescent-shaped with incomplete trophoblastic ring
what is fetus papyraceus?
when a dead fetus is too large to be reabsorbed and is preserved in a distorted shape
during which trimester(s) of pregnancy can fetus papyraceus occur?
2nd or 3rd tri
what is a probable cause for fetus papyraceus?
polyhydramnios of larger twin compresses smaller twin
what type of pregnancy & placentation can fetus papyraceus occur in?
monozygotic pregnancy with monochorionic diamniotic placentation
what is the most common type of abnormal twinning?
conjoined twins
what type of pregnancy and placentation can conjoined twinning occur in?
monozygotic pregnancy with monochorionic monoamniotic placentation
conjoined twins can be different sexes
false
conjoined twins are 70% male
false – 70% female
how does conjoined twinning occur?
if division of ovum occurs after 13 days from conception
what is the most common type of conjoined twinning?
thoracopagus
what is fetus in fetu?
a rare type of conjoined twinning where one twin is in the body of co-twin
where is the location of the parasitic twin in fetus in fetu?
typically in upper retroperitoneum of co-twin; usually seen as an abdominal mass
differential diagnosis of fetus in fetu?
teratoma
U/S appearance of fetus in fetu?
complex mass in abdomen
what does PROM stand for?
premature rupture of membranes
what is the most common complication in the 3rd trimester for multiple gestations?
premature labor with PROM
what is the cause of premature labor with PROM?
overdistension of uterus
some complications associated with premature labor with PROM?
- bleeding due to increase risk for placenta previa, placental abruption, velamentous cord insertion
- maternal HTN
- anemia
- preeclampsia
- eclampsia
- pyelonephritis
what is preeclampsia?
maternal hypertension, proteinuria, and edema after 20th week
what is another name of eclampsia?
toxemia of pregnancy
what is IUGR?
intrauterine growth restriction
- discordant growth between the 2 twins
weight difference of twins with IUGR?
15-20%
500+ gram difference at birth
what measurement is best to assess for IUGR?
abdominal circumference (>20mm)
what is TTTS?
twin to twin transfusion syndrome
abnormal arteriovenous circulation in the placenta with abnormal shunting of blood from one fetus to another
in TTTS the ____ system of donor pumps blood to ____ system of recipient
arterial system; venous system
other names for donor twin?
pump twin; stuck twin
what type of placenta can TTTS occur in?
monochorionic only
in TTTS, what are characteristics of the pump twin?
smaller, oligohydramnios, IUGR, anemic
in TTTS, what are characteristics of the recipient twin?
bigger, polyhydramnios, too much blood, possible CHF
what does TRAP stand for?
twin reversed arterial perfusion
other names for TRAP?
acardiac/acephalic twin
TRAP is a form of TTTS. T/F?
true
what type of placentation is most common with TRAP?
monochorionic monoamniotic
what is interlocking twin syndrome?
a mo-mo pregnancy where one twin is breeched and the other is cephalic
selective termination can only occur with ____ pregnancies
dichorionic
most common method for selective termination?
injection of potassium chloride into fetus’ heart
