Multifetal pregnancy RADIOLOGY

Multifetal pregnancy

1. MULTIFETAL PREGNANCY PRESENTED BY: DR. NITIN WADHWANI DR. D.Y. PATIL HOSPITAL KOLHAPUR

2. DETERMINATION OF CHORIONICITY Determination of chorionicity is best performed very early in gestation, when the gestation sac size is small and the number of distinct sacs can be clearly established. The number of sacs will determine the number of chorions

3. A single gestational sac containing two yolk sacs is a monochorionic pregnancy, and amnionicity then needs to be determined. The number of yolk sacs within a sac was historically thought to accurately predict the number of amnion that is, two yolk sacs in a single gestational sac corresponds with monochorionic diamniotic twins while one yolk sac with two embryos indicates monochorionic monoamniotic twins. However, more recently there have been reports of two yolk sacs leading to two embryos within a single amnion, as well as a single yolk sac leading to two embryos and two separate amniotic sacs.

4. TWIN PEAK SIGN or LAMDA SIGN

5. T SIGN

6. NAMING OF FETUS D etermination is made on the first ultrasound in the second trimester or in the late first trimester at the time of nuchal translucency measurement. F etus whose anatomic part is presenting (i.e., is closest to the cervix) is termed fetus 1 (or A). The non presenting fetus is labeled twin 2 (or B). In larger-order multiples, the location in the uterus is used as an identifying characteristic—triplet 2 is upper right, triplet 3 is upper left, or vice versa. There is no standard method of labeling higher-order births beyond the presenter as number 1

7. AMNIOTIC FLUID ASSESSMENT Assessment of the amniotic fluid volume is performed for each fetus individually. Fluid volume is assessed either subjectively or using the deepest vertical pocket. Occasionally, separation of the intertwin membrane can be appreciated, with amniotic fluid tracking between the membranes. This appearance has not been shown to be associated with an adverse outcome.

8. UMBILICAL CORD ASSESSMENT The umbilical cord of each fetus should be evaluated for the presence of three vessels, as both monochorionic and dichorionic pregnancies have a higher incidence of single umbilical artery than do singletons. T he abnormal cord insertions include both marginal (11% of twins) and velamentous (6%)

9. LOSS OF A TWIN Single intrauterine fetal death (IUFD) occurs in approximately 4% to 7% of twin pregnancies. A fter 22 weeks was twice as high for monochorionic diamniotic as compared to dichorionic twins. After loss of one twin, the surviving twin is at increased risk for adverse outcome, and the risk is again associated with chorionicity, as a result of the vascular anastomoses in a shared placenta.

10. DICHORIONIC MONOCHORIONIC No significant risk in surviving fetus Pre term delivery R isk of severe cerebral injury ( in 25-34%)

11. COMPLICATIONS OF MONOCHORIONICITY Abnormal growth, prematurity, and intrauterine demise seen in monochorionic gestations are all related to the single placental mass that is shared between the two fetuses. The majority of monochorionic placentas have vascular connections that cross back and forth between the two fetal-placental circulations, allowing minute amounts of blood exchange between twins.

12. The anastomoses can be superficial or deep, and there are three distinct types: arterial/arterial (AA) arterial venous (AV) venous venous (VV)

13. TWIN-TWIN TRANSFUSION SYNDROME 10-23% of monochorionic pregnancies It is defined by oligohydramnios (deepest vertical pocket < 2 cm) with a small or empty bladder in the donor and polyhydramnios (deepest vertical pocket >8 cm) with a distended bladder in the recipient in a monochorionic pregnancy S yndrome is usually first identified between 16 and 26 weeks of gestation.

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15. TWIN ANEMIA POLYCYTHEMIA SEQUENCE ( TAPS) TAPS occurs when there is sufficient unequal passage of red cells via the placental anastomoses such that one twin becomes anemic (the donor) and one becomes polycythemic (the recipient). Seen in 5% of monochorionic twins.

16. The transfusion occurs extremely slowly via tiny unidirectional AV anastomoses, over a long period of time

17. T he diagnosis of TAPS is made prenatally with Doppler interrogation of the middle cerebral artery in each fetus The anemic fetus will demonstrate elevated peak systolic velocity in the middle cerebral artery (>1.5 multiples of the median), while the polycythemic fetus demonstrates decreased velocities (<1.0 multiples of the median)

18. TWIN REVERSED ARTERIAL PERFUSION SEQUENCE (TRAPS) Occurs when one twin has an absent or severely malfunctioning heart and there is a large unbalanced AA anastomosis within a monochorionic placenta.

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20. MONOAMNIOTIC TWINS B oth fetuses are located within a single amnion and therefore a single chorion Monoamniotic twins should be suspected when no intertwin membrane is identified by 10 to 12 weeks’ gestational age and can be confirmed at any age when the umbilical cords are seen to twist together or become entangled

21. Monochorionic Monoamniotic Twins, 12 Weeks’ Gestational Age

22. CONJOINED TWINS R are type of monoamniotic twins that occur with late division of the embryo (>14 days) T he twins can be conjoined at any skin site and are diagnosed by demonstrating contiguous skin covering between two fetuses

23. Conjoined twins can be diagnosed in the late first trimester however, a detailed survey will be required by 18 to 20 weeks’ gestation for the most accurate evaluation of the degree of visceral and vascular sharing T he umbilical cord may also be fused, with more than three vessels seen within a single cord.

24. Monochorionic Monoamniotic Conjoined Twins, 35 Weeks’ Gestational Age.