Multifetal Gestations and Malpresentation Flashcards
What is multiple gestations defined as?
- Any pregnancy in which two or more embryos or fetus occupy the uterus simultaneously
- Have increased over the years secondary to ovulation induction agents and assisted reproductive technology
What are dizygotic twins?
- Arise when two separate ova are fertilized by two separate sperm
- Are distinct pregnancies coexisting in the same uterus
- Each will have its own amnion, chorion, and placenta
What are monozygotic twins?
- Arise from cleavage of a single fertilized ovum at various stages during embryogenesis
- Thus the arrangement of fetal membranes and placentas will depend on the time at which the embryo divides
What is the nature of the membrane if monozygotic twins separate at 0-3 days?
- Dichorionic
- Diamniotic
What is the nature of the membrane if monozygotic twins separate at 4-8 days?
- Monochorionic
- Diamniotic
What is the nature of the membrane if monozygotic twins separate at 9-12 days?
- Monochorionic
- Monoamniotic
What is the nature of the membrane if monozygotic twins separate at >13 days?
- Conjoined twins
What is the placenta like when monozygotic twins split at 0-3 days?
- Could be separate but could be fused
What is the most common presentation of monozygotic twins?
- 1 chorion and 2 amnions
- Splitting in 4-8 days
What is the most dangerous cleavage of monozygotic twins?
- Cleavage in 9-12 days
- 1 chorion and 1 amnion
- Most dangerous because they are not separating amnions which leaves high risk for cord entanglement
- High net mortality in these twins
What is craniopagus?
- Conjoined twins at the head
What is thoracopagus?
- Conjoined twins at the chest wall
- Highest incidence of conjoined twins
What is ischiopagus?
- Conjoined at the coccyx and sacrum
What is the epidemiology of monozygotic twins?
- Frequency is constant in all populations at 1 in 250
What can influence dizygotic twins?
- Maternal age: 2x more common after 35 years old
- Family history and ethnicity: twinning is low in asians, intermediate in whites and high in blacks
What may a history and physical look like for multiple gestations?
- hCG is higher than normal
- Uterus palpates larger than dates
- Auscultation of more than one fetal heart rate
- Pregnancy has occured after ovulation induction or in vitro fertilization
What confirms the presence of multiple fetus?
- Ultrasound
- Determine the number of fetuses, gestational sacs and chorionicity
What are monozygotic twins more at risk for?
- Congenital anomalies
- Weight discordancy
- Twin-twin transfusion syndrome
- Neurologic sequelae
- Premature delivery
- Fetal demise
What it the most important step after finding out about multiple gestations?
- Determination of zygosity
What will be seen under ultrasound that points towards dizygotic twins?
- Different fetal genders
- Visualization of a thick amnion-chorion septum
- “Peak” or “inverted V” sign at the base of the septum
What will be seen under ultrasound that points towards monozygotic twins?
- Dividing membrane is fairly thin
What is done if ultrasound is not definitive in determining zygosity?
- Inspect placenta after delivery
- DNA analysis
What is the mortality rates of conjoined twins?
How are they delivered?
- 50%
- Delivered via C section
What will imaging show for conjoined twins?
- Mapping of shared organs allows for more successful surgical separation procedures
- Elective termination is done if cardiac or cerebral fusion is identified
What are interplacental vascular anomalies?
- Most common type is arterial-arterial followed by arterial-venous and then venous-venous
- Vascular communications between the 2 fetuses through the placenta can cause several problems (abortion, polyhydramnios, TTTS, and fetal malformations)
What does twin twin transfusion syndrome result from?
- Secondary to uncompensated arteriovenous anastomoses in monochorionic placenta which leads to a net transfer of blood flow going from one twin to the other
What fetal complications are seen in the donor twin in twin twin transfusion syndrome?
- Hypovolemia
- Hypotension
- Anemia
- Oligohydramnios
- Growth restriction
What fetal complications are seen in the recipient twin in twin twin transfusion syndrome?
- Hypervolemia
- Polyhydramnios
- Thrombosis
- HTN
- Polycythemia
- Edema
- Cardiomegly/CHF
What are both twins at risk for in TTTS?
- Heart failure causing death
What is seen in ultrasound in TTTS?
- Donor twin: smaller in size, “stuck appearance, oligohydramnios
- Recipient twin: larger in size, polyhydramnios, ascites
How is TTTS treated?
- Serial amniocentesis with amniotic fluid reduction
- Can reduce preterm contractions secondary to uterine distention (polyhydramnios) and maternal symptoms
- Laser photocoagulation of the anastomosis vessels on the placenta is performed at specialized centers
What is an aretial to arterial anastomomes?
- Arterial blood flow from the donor twin enters the arterial circulation of the recipient twin
- The reversed blood flow may cause thrombosis within critical organs or atresias due to trophoblastic embolization
- Recipient twin, being perfused in a reverse direction with poorly oxygenated blood fails to develop normally (Known as arcardic twin)
What is an arcadic twin?
- Recipient twin that is poorly perfused due to reverse blood flow direction
- Fully formed lower extremities
- No anatomic structures cephalad of the abdomen
What umbilical cord abnormalities could be seen in multiple gestations?
- Primarily associated with monochromatic twins
- Absence of umbilical artery (30% of cases is associated with other congenital anomalies like renal agenesis)
- Velamentous umbilical cord insertions occur more frequently and may cause growth abnormalities
What is retained dead fetus syndrome?
- Incidence of a single fetal death in utero is 5%
- If gestation is 20 weeks or greater retained dead fetus syndrome can develop due to disseminated intravascular coagulopathy in mother (check platelets and fibrinogen weekly)
What happens in retained dead fetus syndrome if gestation is <12 weeks?
- Fetus is reabsorbed called “vanishing twin syndrome”
What happens in retained dead fetus syndrome if gestation is >12 weeks?
- Fetus shrinks, dehydrates, and flattens called fetus papyraceus
What are some maternal complications with multiple gestations?
- Polyhydramnios
- Anemia
- Gestational HTN
- Preeclampsia
- Preterm labor
- Gestational diabetes
- C section
- Postpartum hemorrhage
- Uterine atony
What are some fetal complications with multiple gestations?
- Prematurity
- Malpresentation
- Placenta previa
- Placental abruption
- PROM
- Umbilical cord prolapse
- IUGR
- Congenital anomalies
- Increased perinatal morbidity and mortality
What is the antepartum management in multiple gestations during the first and second trimesters?
- 2 week office visits
- Ultrasound cervical length assessments
What is the antepartum management in multiple gestations during the third trimester?
- Cervical length of less than 25mm at 24-28 weeks doubled the risk of for premature births in twins
- Serial ultrasounds to check for intrauterine growth every 4-6 weeks begin at 24 weeks looking for discordant fetal growth
- Antepartum testing
- Often placed on bed rest
When should monoamniotic twins be delivered? Why?
- At 32 weeks
- Secondary to increase risk for lethal cord entanglement
When do a majority of twin gestations deliver?
- 35-36 weeks
- 38 weeks if no complications
What are prerequisites for intrapartum management?
- Delivery room equipped for immediate cesarean section
- Large IV bore needle, blood products
- Capability to monitor fetal heart rates simultaneously
- Anesthesiologist immediately available
- Ultrasound to determine precise presentations of twins
- Two pediatricians/NICU personnel, one for each baby
- Appropriate number of nurses to assist in delivery and care
What is the process of delivery in a vertex-vertex presentation?
- After delivery of the first twin, cord is clamped and cut
- Vaginal examination is performed to assess presentation and station of second twin
- Careful attention to fetal monitoring is necessary
- After second twin delivers obtain cord samples and deliver placenta
- Be prepared for postpartum hemorrhage secondary to uterine atony
What is the second twin at risk for in a vertex-vertex presentation?
- Cord prolapse
- Placental abruption
- Malpresentation
How are vertex-transverse and vertex-breech presentations delivered?
- Able to be done vaginally but often by C sections
- No evidence that C section is superior but there is a difficulty in extracting breech second twin
What could result during delivery of a breech second twin?
- Umbilical cord prolapse
- Head entrapment
- Neck injury
- Asphyxia
How are breech-breech or breech-vertex twins delivered?
- C section
What are some perinatal outcomes in twins?
- High perinatal mortality rate 5x greater than in singletons secondary to prematurity and congenital anomalies
- Stillbirths occur 2x more frequently
- 4x increase in cerebral palsy
- Postnatally twins are on average shorter and lighter than singletons of same birth weight
What is the perinatal mortality due to in twins?
- RDS and intracranial hemorrhage
- Birth asphyxia
What can higher order multiples result from?
- Embryo splitting and polyovulation
- Most frequently a result of iatrogenic causes
How does prematurity increase in higher order multiples?
- Triplets are delivered at 33 weeks via C section
- Quads are delivered at 29 weeks via C section
What are some fetal malpresentations?
- Any fetal presentation other than vertex
- Breech
- Face
- Brow
- Shoulder
- Compound
What is the breech presentation?
- Fetal buttocks or lower extremities present into the maternal pelvis
What are some factors associated with fetal breech?
- Prematurity is most common factor
- Fetal malformation –> hydrocephaly and anencephaly
- Multiple pregnancies
- Uterine malformations –> bicornuate uterus
How is a breech presentation diagnosed?
- Leopolds maneuver
- Ultrasound and pelvic exams
What is the frank breech presentation?
- Most common presentation
- Thighs flexed
- Lower extremities are extended at the knee
What is the complete breech presentation?
- Thighs are flexed
- Lower extremities are flexed
What is the incomplete breech presentation?
- 1 or both thighs are extended
- 1 or both feet are below the buttocks
What is external cephalic version?
- Involves applying pressure to the mother’s abdomen to turn the fetus in either a forward or backward somersault to achieve vertex presentation
Who are candidates for the ECV?-
- 36 week gestation not in labor
What are some contraindications of ECV?
- Placental previa
- Nonreassuring fetal monitoring
- Oligohydramnios
- Previous uterine surgery that is a contraindication for vaginal delivery
How is the ECV performed?
- In a hospital that is equipped for an immediate C section
- Patient should be NPO x 7hrs
- Review risks, benefits, alternatives and obtain consent
- IV access
- Place on continuous electric monitoring
- Confirm breech presentation with ultrasound
- Consider tocolytics or anesthesia
- Perform procedure
What is the criteria for vaginal delivery of breech presentation?
- Fetus must be in frank or complete presentation
- Gestational age >37 weeks
- Fetal head must be flexed
- Adequate maternal pelvis
- No maternal or fetal contraindications for vaginal delivery
- Availability of anesthesia and neonatal support
- Assistant must be scrubbed and prepared to assist
What is important when doing a breech vaginal delivery?
- Allow fetus to deliver to scapulae
- Premature aggressive traction can cause deflexion of the fetal vertex and increase risk of head entrapment or nuchal arm entrapment
What is done to the fetus after it has expulsed to the scapulae?
- External rotation of each thigh combined with opposite rotation of the fetal pelvis results in flexion of the knee and delivery of the leg
- Wrap a towel around the fetus for better traction
- When the scapulae appear under the symphysis
- The operator reaches over the left shoulder, sweeps the arm across the chest and delivers the arm
How is delivery of the head achieved in a breech presentation?
- Often delivery of head is easily accomplished with continued uterine contractions, suprapubic pressure, and gentle traction
- Maintain cephalic flexion by applying pressure on fetal maxilla NOT fetal mandible
What is the prefered delivery method for breech presetnations?
- C section due to the risk of fetal head becoming entrapped and leading to fetal asphyxia with increased morbidity and mortality
What is the brow presentation?
- Presenting part of fetus is between the facial orbits and anterior fontanelle
- Presenting diameter is supraoccipitomental diameter
- Frontal bones are the point of designation
Can a brow presentation be delivered vaginally?
- No, very difficult
- Deliver by C section
How can a brow presentation be altered to allow a vaginal delivery?
- Go into extension for a face presentation
- Go into flexion for a vertex presentation
What is the supraoccipitomental diameter?
- 13.5 cm
What is the face presentation?
- Full extension of the fetal head and neck with occiput against upper back
- Can be seen in fetal malformations like anecephly
What is the point of designation in the face presentation?
- Chin
- 60% of mentum anterior allows for a vaginal delivery
What is the trachelobragmatic diameter?
- 12.6 cm
What are some compound presentations?
- When a fetal extremity is found prolapsed alongside the presenting fetal part (head)
- More frequently in premature gestation
- May resolve on its own as it comes down the pelvis
- C section done if failure to progress, cord prolapse, or nonreassuring fetal status is noted
