Twinning Flashcards
Twinning
-3% of all pregnancies
-2 types:
-dizygotic twins -> arise from fertilization of 2 ova and 2 sperm
-monozygotic twins -> arise from error in cell division after fertilization of 1 ovum and 1 sperm
morbidity and mortality in multifetal gestations
risk factors in twinning
-Increased maternal age
-Increased paternal age (less of a factor than maternal age)
-Assisted reproductive technology
-Increased parity
-Family history of twinning -> Maternal family history>paternal family history
-Taller and heavier patients are more likely to bear twins
maternal complications of twinning
-Hyperemesis
-Gestational diabetes mellitus
-Hypertensive disorders of pregnancy -> Occurs earlier in pregnancy compared to singleton gestations
-Anemia
-Intrapartum or postpartum -hemorrhage
-Cesarean section
-Postpartum depression
MC complication of twin or multifetal gestation is
prematurity
dizygotic twins
-Result from two ova and two sperm
-Really are siblings who share the uterus at the same time
-May not have the same birthdate!
-May not have the same father!
-Incidence worldwide: about 4/1000 births
monozygotic twins
-Result from one ovum, one sperm, and an error in cell division
-Unless there has been a postzygotic mutation, they are always the same gender
-The resultant type of twins depends on when the error in cell division occurred
-Dichorionic/diamniotic (two placentae, two sacs)
-Monochorionic/diamniotic (have one shared placenta but separate sacs)
-Monochorionic/monoamniotic (have one placenta and one sac)
-Conjoined twins
-Incidence varies with population
dichorionic/diamniotic (di-di)
-Error in cell division occurs by the third day after conception
-Have separate amniotic sacs and separate placentae
-Despite the illustration at R, 10% of di-di twins are “identical”, or monozygotic
-However, all dizygotic twins will be “di-di”
-They also have the best prognosis of any type of twin gestation
monochorionic/diamniotic (mono-di)
-Error in cell division occurs 4-8 days after conception
-Have two separate sacs but one placenta
-Virtually all are monozygotic unless there has been fusion of the blastocyst
-Increased risk of twin-to-twin transfusion syndrome
monochorionic/monoamniotic (mono-mono)
-Error in cell division after the 9th day after conception
-One sac, one placenta
-Greatly increased risk of intrauterine death in part due to cord accidents
-Survival=50-60%
-Risk of congenital anomalies is as high as 28%
conjoined twins
-Error in cell division occurs after the 12th day following conception
-Females»males
-dont need to know
twin to twin transfusion syndrome
-Seen in monochorionic gestations only, most commonly monochorionic, diamniotic
-Occurs because of a vascular anastomosis in the placenta with development of a shunt between fetuses
-Occurs in 1-3/100,000 births
-Blood can be shunted from one twin (donor) to the other twin (recipient)
-Dangerous for each twin
-Donor twin may develop: intrauterine growth restriction and anemia
-Recipient twin may develop: hydrops, CHF, HTN, polycythemia, hyperbilirubinemia, kernicterus
mechanism of twin to twin transfusion syndrome
-The donor twin develops decreased renal perfusion, resulting in oligohydramnios
-However, the recipient twin develops polyhydramnios
-With severe polyhydramnios, decreased cardiac motion in the donor twin can result due to compression from the recipient twin’s sac
-Polyhydramnios-oligohydramnios syndrome (“poli-oli”)
-sac of one baby can get so big it impinges on the otehr
management of twin to twin transfusion syndrome
-serial amnioreduction
-fetoscopic laser photocoagulation
-selective feticide
managing multiple gestations
-Early sonography to diagnose chorionicity
-Serial ultrasounds every 2 weeks in monochorionic gestations
-Increase maternal diet by 300 kcal/day per additional fetus
-Fe2+ supplementation (to reduce risk of maternal anemia following increased blood loss at delivery)
-Consider following cervical length via vaginal exams and cervical ultrasound, if desired
-Antenatal steroids between 24-34 weeks GA should be administered to patients at risk of delivery within 7 days
which type of dizygotic twin gestation occurs prior to 3 days after conception
-dichorionic, diamniotic!!!
-monochorionic, diamniotic
-monochorionic, monoamniotic
-conjoined
