15. Multifetal Gestation and Malpresentation Flashcards
What is multiple gestation?
2 or more embryos/fetus are in the uterus at the same time.
What are fraternal twins?
- Dizygotic twins that form when 2 diff sperm fertilize two diff ova => 2 pregnancies in 1 uterus => each as own amnoin, chorion and placenta
What are identical twins?
- Monozygotic twins that occur when 1 fertilzed ovum CLEAVES at different stages of embryogenesis.
How does the nature of the membranes for monozygotic twins change if the embryo is cleaved at 0-3, 4-8, 9-12, or >13 days?
- 0-3 days = dichorionic, diamniotic (separated)
- 4-8 days = monochorionic, diamniotic
- 9-12 days = monochorionic, monoamniotic
- >13 days = conjoined twins
What is the most common presentation of membranes for monozygotic twins?
Monochorionic, diamniotic (1 choroin and 2 amnions) due to cleaveage at days 4-8
In dichorionic, diamniotic monozygotic twins, which form when embryo splits at days _____, what type of placentas do they have?
0-3 days
seperate or fused
Which presentation of monozygotic twins is the most dangerous and why?
Monochorionic monoamniotic bc their are not seperate amnoins, which can result in cord entanglement.
If the embryo splits at 13-15 days => monochorionic/monoamnionitic (conjoined twins) are formed with 1 placenta and 1 choroin.
How are they defined?
By where they are connected.
- Craniopagus => head
- Thoracopagus => chest wall (MC)
- Ischiopagus (coccyx and sacrum)
2/3’s of spontaneous twins are (mono- or dizygotic)?
Dizygotic (fraternal)
Having dizygotic twins is 2x more common when?
In what races?
- After 35 YO
- Highest in blacks = low in asians.
When should you suspect multiple gestations based on hCG, size of the uterus, ascultation?
- Higher than NL (more than 2x/every 2 days)
- Uterus palpates larger than date
- Ausculate more than 1 fetal heart
How do we confirm multiples?
US:
- Determine number of fetuses, gestational sacs and chorions
What is the most important step after diagnosing a twin pregnancy?
Determine zygosity, because prognosis and morbidity is dependent.
Monozygotic twins have increased incidence of what?
- Congenital anomalies and neuro problems
- Weight discordancy
- TTTS (twin-twin transfusion syndrome)
- Premature delivery
- Fetal demise
How can a dizygotic twins be determined on U/S?
- Different genders
- Thick amnion-chorion septum
- “Peak” or “inverted V” sign at base of septum
How can monozygotic twins be determined on US?
Fairly thin dividing membrane
If US does not determine zygosity, what do we do?
- Inspect placenta after delivery
- DNA analysis
90% of interplacental vascular anastomoses occur in what type of twins and what is the most common type of anastomosed vessels?
- 90% occur in monochorionic twins
- Most common type is arterial-arterial > arterial venous > v-v
Interplacental vascular anastomosis (vascular communition between 2 fetuses through placenta) can cause what complications?
- Abortion
- Polyhydramnois
- TTTS
- Fetal malformation
How are conjoined twins delivered?
When is elective termination performed?
- C-section
- Cardiac/cerebral fusion is found
What is twin-twin transfusion syndrome?
Uncompensated arterial-venous anastomoses in a monochorionic placenta, causing net transfer of blood from 1 twin to the other.
What are treatment options for twin-twin transfusion syndrome?
- Laser photocoagulation of the anastomosis vessles on the placenta is performed nowadays
- Serial amniocentesis w/ amniotic fluid reduction has been historically done
What complications do we see in the donor twin in TTTS?
- Net loss of blood
- Hypovolemia
- Hypotension
- Oligohydramnois
- Anemia
- Growth restriction
What complications do we see in the recepient twin in TTTS?
-
Receives blood
- Hypervolemia/edema
- HTN
- Polydramnois
- Polycythemia
- Cardiomegaly/ CHF
In twin-twin transfusion syndrome both twins are at risk of demise from what?
Heart failure
How is TTTS diagnosed and what is seen in the donor twin vs recepient?
- US
- Donor: smaller, stuck in appearance and oligohydramnois
- Recep: larger, polyhydramnois, ascites
What occurs in Acardiac Twin?
- Arterial to arterial anastomoses between twins
- Recipient twin is perfused w/ poor oxygenated blood => thrombosis/atresia of organs => fails to develop normally
=> ACARDIAC TWIN => Fully formed LE’s w/ NO anatomic structures above of abdomen
What is the most common umbilical cord abnormalities, which are MC in monozygotic twins?
Velamentous umbilical cord insertions > no umbilical as.
If retained dead fetus syndrome occurs >20 weeks gestation, what complication can develop in the mother; how should she be managed?
- Can devlop DIC
- So check platelets and fibrinogn levels weekly
What is fetus papyraceus?
When retained dead fetus syndrome occurs >12 weeks and the fetus shrinks, dehydrates, and flattens
What is vanishing twin syndrome?
When retained dead fetus syndrome occurs < 12 weeks, dead fetus is reabsorbed.
Maternal complications of multiple gestations
- Polyhydramnois
- Anemia
- Gestational HTN/DB
- Post-partum hemorrhage d/t uterine atony
- C-section and preterm labor
When should mother with monoamniotic twins be hospitalized and they should be delivered at how many weeks; WHY?
- Hospitalize at 26 weeks (give steroids and monitor FHR several times a day) and deliver at 32 weeks
- Secondary to ↑ risk of lethal cord entaglement
How do you manage multiple gestations in the 1st and 2nd trimester?
- Visit doc office every 2 weeks
- US cervical length assessment
How do you manage multiple gestations in the 3rd trimester?
- Cervical length
- Serial US q 4-6 weeks begining at 24 weeks to look for discordant fetal growth (20% reduction in fetal weight of smallest fetus compared to largest)
- Antepartum testing (NST or weekly BPP)
- Bed rest
NST rate of stillbirth
BPP rate of still birh
- NST = 1.9%
- BPP = 0.7%
If no complications during pregnancy, it is recommended to deliver twins at how many weeks?
38 weeks, but most are delivered at 35-6.
What is the best presentation to deliver twins vaginally?
Vertex-vertex
During vertex-vertex presentation the 2nd twin is at increased risk for what complications; we should be prepared for what complication in mom?
- 2nd twin = ↑ risk of cord prolapse, placental abruption, and malpresentation
- Be prepared for postpartum hemorrhage due to uterine atony
If first twin is vertex, but other twin is transverse/breech how should they be delivered?
CAN be vaginally, but will often be by C-section
How are breech-breech or breech-vertex twins delivered?
C-section
What is the perinatal mortality in twins compared to singletons and why?
- 5x greater due to prematurity and congenital anomalies (respiratory distress syndrome, intracranial hemorrhage and birth asphyxia => 2nd twin is more likely to die).
How are triplets/quads delivered?
C-section
More than 2 fetuses
- Most commonly due to _________.
- As the number of fetuses increase => prematurity increases
- Triplets delivered at ______ weeks
- Quads delivered at ____ weeks
- Iatrogenic causes (agents that induct ovulation)
- Triplets => 33 weeks
- Quads => 29 weeks
What is malpresentation and what is the most common?
Presentation other than vertex
BREECH is the most common.
What is the most common breech presentation?
- Frank
- Thighs are flexed
- Knees are extented
What is breech and what is the most common factor associated with breech?
- BBs butt or LE presents in pelvis
- Prematurity
How are breech presentation dx?
- Leopold maneuver
- US
- Pelvic exam
What happens if a women wants a vaginal delivery, but is in breech presentation?
Where must it be done
ECV (external cephalic version) => turn bb forward or backward summersault into vertex position if they are at 36 weeks and NOT in labor.
- must be done in a hospital where an immediate c-section can be done-
CI for ECV
- Oligohydramnois
- Non- reassuring fetal monitoring
- Placental previa
- Previous uterine sugery
Before performing external cephalic version (ECV) patient should be NPO for how long?
7 hours
What is the standard of care in most practices in terms of how to deliver a breech presenation?
All by C-section
What did the 2000 Term Breech Trial say about delivering breech vaginally?
Found that in planned c-section groups = neonatal mortality/morbidity, but no difference in maternal morbidty/mortality.
If doing a vaginal breech delivery how far should the baby be out before applying any traction?
Allow fetus to deliver to the scapulae
Traction too early can cause head deflexion => head entrapment.
If doing a vaginal breech delivery, how do you deliver the head?
- Apply pressure on fetus MAXILLA to keep the head flexed.
- But often head is easily delivered with contractions, suprapubic pressure and gentle traction
Which special type of forceps are used in assisted breech vaginal deliveries?
PIPER forceps
Why are c-sections ESPECIALLY done in premature breeches?
bc largest part of fetus is head => can get entrapped => fetal asphyxia
BROW PRESENTATION
- What is it?
- How are they delivered.
- Presenting part of the fetus is the supraoccipitomental diameter (between the facial orbits and anterior fontanelle) = 13.5 cm
- Deliver
- Most extend to face presentation or flex to vertex => deliver
- If brow persists => MUST do c-section
What is face presentation?
What is seen in 1/3 of the cases?
- Head and neck are fully extended, with the occiput against the upper back
- Anecephaly
With a face presentation the fetal chin is the point of designation. Which of these babies CAN and which CANNOT be delivered vaginally?
- Mentum anterior => vaginally (MA can deliver vainally)
- Mentum posterior=> C-section
what is the presenting part in face presentation?
Trachelobragmatic diameter (12.6)
What is a compound presentation?
delivery?
When fetal extremity (usually the hand) is found prolapsed alongside the presenting fetal part (head)
Delivery
- May resolve on its own as it goes into pelvis
- if not => c-section
