Recommended
More Related Content
Similar to Multifetal Pregnancy.pptx
Similar to Multifetal Pregnancy.pptx (20)
Recently uploaded
Recently uploaded (20)
Multifetal Pregnancy.pptx
- 1. MultiFetal Pregnancy Presented by – Dr.Sachin Sharma PG Resident -1 Dept. of Radio-Diagnosis
- 2. Introduction • Two or more fertilization events. • Single fertilization followed by splitting of zygote. • Combination of both
- 3. • Global incidence : 4/1000 births • Hellin’s Law : Twins: 1/80 singleton births Triplets: 1:802 Quadruplets: 1:803 • Conjoined twins: 1:60,000
- 4. Impact • Twins account for 17% of all preterm births 24% of low birth-weight infants (<2,500 g) and 26% of very-low-birth-weight infants (<1,500 g) • Women with twin pregnancy are 6 times more likely to be hospitalized with complications.
- 5. •Multifetal pregnancies, in addition to the risks seen in singleton pregnancies are also at particular risk of •Premature delivery and •Growth restriction.
- 6. Zygosity/Chorionicity • Twins are either • Dizygotic (fraternal) or • Monozygotic (identical). • Among spontaneous twins, • 2/3rd are Dizygotic and • 1/3rd are Monozygotic.
- 7. • Dizygotic twins:- • When two separate ova are fertilized by two separate sperm. • The rate of dizygotic twinning varies with maternal age , race, and family history. • Monozygotic twins:- • When an ovum is fertilized by a single sperm and the embryo then divides from 2 to 14 days after fertilization. • The timing of the division will dictate the type of twin.
- 8. Monozygotic twins • Uniform across the world (3.5/1000) • Not affected by maternal age , race or other known factors. • 2 to 12 times increase following in vitro fertilization. • In ART, timing of transfer can affect rate of monozygotic twins, • Higher rate following 5-6day transfer than 2-3day transfer. • Higher rate in assisted hatching.
- 10. • Management depends on Chorionicity than Zygosity. • Chorionicity is responsible for complications with monochorionic pregnancies at highest risk. • So, Chorionicity should be accurately determined.
- 11. Dizygotic Twins • Dizygotic twins are always dichorionic diamniotic • Each twin exists in a separate intrauterine environment and are genetically different.
- 12. Monozygotic Twins • Have three possible variations of chorionicity who are genetically identical. • If Division occurs - • Within 4 days – DCDA (1/3rd cases.) • 4-7 days – MCDA (2/3rd cases.) • 7-14 days – MCMA ( 1%). • > 14 days – Siamese (Conjoint Twins).
- 14. • Risk – Chorionicity > Zygosity , USG plays critical role. • Chorionicity easily and accurately determined in 1st Trimester. • Determine chorionicity and amnionicity for each embryo.
- 16. Determination of Chorionicity. • USG plays key role beginning with 1st trimester. • TVS approach standard for early pregnancy(<8 wks.) • Chorionicity is determined very early when G-sac is small, and no. of sacs are clearly visible. • No. of sacs = No. of Chorion. • Evaluate each sac for yolk sac, embryo, and C.A. • Carefully evaluate contents of each sac.
- 17. Gestational Age. • 1st trimester USG is highly accurate at dating pregnancy , important for multiple gestations. • Initial USG report must clearly define • Type of gestation, including chorionicity for each embryo, and • Should provide a single gestational age. • Patients who conceived via IVF , gestation age = embryo transfer date. • For spontaneous multiples, • If embryo size is similar , take avg. of CRL for accurate gestational age. • If size of embryos are significantly different , take CRL of largest embryo.
- 18. • Potential pitfall in early assessment of multiple gestations is “Appearing Twin.” • In contrast, because of the high background loss rate in the first trimester, twins may also “vanish.”
- 19. • 2 G-sac within endometrial cavity = Dichorionic twin. • Single G-sac having 2 yolk sac = Monochorionic pregnancy. • USG is most accurate for assigning chorionicity in pregnancies less than 14 weeks.
- 23. Twin Peak Sign / Lambda Sign / Delta Sign Intertwin Membrane.
- 25. Identification of Fetus. • The fetus whose anatomic part is presenting ,is termed as fetus 1/A. • Should remain fetus 1/A for rest of pregnancy. • Non presenting fetus is termed fetus 2/B. • In larger-order multiples, location in the uterus is used—triplet 2 is upper right, triplet 3 is upper left, or vice versa. • Other clues for identifying fetus are • placental location, • sex, • discordant growth, and • any potential anomaly.
- 26. • Amniotic fluid volume assessment is done for each fetus individually, either subjectively by an experienced examiner or using DVP. • DVP – 2- 8 cm in a single pocket. • Umbilical artery of each fetus must be checked for 3 vessel presence as both MC and DC pregnancies have higher incidence of SUA. • Abnormal placental insertions (should be reported for each fetus) – • Marginal. • Velamentous.
- 27. A)Marginal Placenta B)Velamentous Placenta
- 29. General Issues • Twin pregnancies have higher rates of perinatal morbidity and mortality. The risk is closely related to chorionicity. • Complications include • Premature delivery, • Intrauterine growth restriction, and • Intrauterine demise of one or more foetuses.
- 33. General Issues • Risk of spontaneous loss of both fetuses – • MC > DC , • In MC twins - MCMA than in MCDA. • Twin fetuses are smaller than singletons, MC twins are more affected. Differences are most profound after 30 weeks’ gestation. • Altered growth in MC twins is related to unequal placental sharing, • In DC twins, altered growth is due to a more or less favorable uterine implantation site.
- 34. • USG fetal weight estimation in twins and triplets is very accurate, so it is used to monitor multiple gestations. • Increased risk of fetal loss is seen with discordant fetal weights. • Discordant fetal weights – EFW of smaller twin falls under 10th centile. • Formula= Larger twin estimated weight − smaller twin estimated weight × 100. Larger twin estimated weight
- 35. LOSS OF A TWIN • Single IUFD – 4 to 7 % twin pregnancies. • MC>DC. • More the weight discordance, greater is IUFD. • Subsequent twin also dies in few case (MC>DC). • In DC gestation with single IUFD, no significant risk of injury to the surviving fetus, but causes increased rate of preterm delivery. • In MC twins with a single IUFD – increased risk (25 to 34%) of severe cerebral injury.
- 36. • When 1st fetus expires, there is a sudden drop in vascular resistance across the placental anastomoses and blood is shunted away from the survivor, causing anemia, hypotension, and hypoperfusion of vital organs. • Sonographic manifestations of cerebral ischemia – • Intracranial haemorrhage, • Middle cerebral artery infarction, and • Periventricular white matter injury with subsequent leukomalacia. • TTTS + Single IUFD = survivor twin at higher risk of cerebral injury.
- 38. Complications of Monochorionicity • Monochorionic placentas have vascular connections that cross back and forth between the two fetal-placental circulations, allowing minute amounts of blood exchange between twins. • Anastomosis – Deep or Superficial. • Types – • AA – Bidirectional , small (87%). • AV – Unidirectional , deep (94% of monochorionic placentas). • VV – Bidirectional , superficial.
- 39. TWIN TO TWIN TRANSFUSION SYNDROME (TTTS) • Oligohydramnios (DVP< 2 cm) with a small/empty bladder in the donor and polyhydramnios (DVP > 8 cm) with a distended bladder in the recipient in monochorionic pregnancy. • It is aka “twin oligohydramnios/polyhydramnios syndrome.” • More VV anastomosis. • AA anastomosis is protective. • First identified in 16th to 26th wk. gestation. • Management - Fetoscopic ablation of vascular anastomosis.
- 43. Twin Anemia and Polycythemia Syndrome (TAPS) • Unequal RBC passage via placental anastomosis. • One twin becomes anemic (donor), and one becomes polycythemic (recipient). • Occurs via AV anastomosis. • Discordance not as great as in TTTS. • Diagnosis is done prenatally by color doppler of MCA. • Anemic fetus – elevated peak systolic volume in MCA (> 1.5 times multiples of meridian). • Polycythemic fetus – decreased velocities (< 1.0 multiples of meridian).
- 44. Twin Reversed Arterial Perfusion Sequence (TRAP) • Occurs when one twin has absent/malfunctioning heart and large unbalanced AA anastomosis within a monochorionic placenta. • Blood flow from pump twin through placenta into umbilical artery in second twin causing reversal of flow in umbilical artery. • VV anastomosis then takes blood back to pump twin. • Recipient is termed as “Acardiac Twin”
- 47. • So, Twin Pregnancy can increase risk of – • Preterm labor. • IUFD • TTTS • TAPS • TRAP
- 48. THANK YOU
Editor's Notes
- Good Morning respected Teachers , Seniors and my fellow residents. Today I am presenting a seminar on Multifetal pregnancy
- Multifetal pregnancy is defined as two or more fertilization events or single fertilization followed by splitting of zygote or combination of both.
- Premature Delivery - is that when a baby is born too early, before 37 weeks of pregnancy. Growth Restriction – is when a baby is born weighing less than 90 percent of other babies at the same gestational age
- Spontaneous monozygotic twinning is uniform across the world (3.5/1000) Not affected by maternal age , race or other known factors. An increased incidence of monozygotic twins from 2 to 12 times is seen following in vitro fertilization. In patients undergoing ART, timing of single embryo transfer can affect the rate of monozygotic twins. Higher rate is seen following a 5-6day transfer as compared to 2-3day transfer. Higher rate is seen in patients who have undergone assisted hatching. Assisted Hatching - is a procedure where we can help the embryo “hatch” from its “shell” by creating a small crack in the zona pellucida.
- Here in this diagrammatic representation , When single sperm fertilizes single ovum and then the fertilized egg splits into two are called monozygotic twins. And when two separate sperms fuse with two separate ova leads to formation of Dizygotic twins.
- For management of a twin pregnancy, the type of twin is characterized by chorionicity rather than zygosity. Chorionicity is the major determining feature for the inherent unique complications faced by multiple gestations, with monochorionic pregnancies at the highest risk. Therefore accurate determination of chorionicity is critical to ensure appropriate obstetric management of a twin pregnancy.
- Dizygotic twins are always dichorionic diamniotic, meaning that each twin has its own placenta (chorion), amnion, and amniotic fluid. Each twin exists in a separate intrauterine environment, and the twins are genetically different.
- In contrast, there are three possible variations of chorionicity for monozygotic twins, who are genetically identical. Twins that occur when a single zygote divides within the first 4 days after fertilization have their own placenta , amnion, and amniotic fluid (called dichorionic diamniotic, seen in one-third of cases). Monozygotic twins that occur from a later division share a placenta, but each has its own amnion (called monochorionic diamniotic, seen in two-thirds). When the division occurs between days 7 and 14, the twins will share a placenta , amnion, and amniotic fluid (called monochorionic, monoamniotic, seen in approximately 1%). Any later time of division , usually more than 14 days will result in conjoined twins.
- This is the Diagram Illustrating Zygosity and Placentation in Twins. Of twin gestations, two-thirds are dizygotic, and one-third are monozygotic. All dizygotic twins result in diamniotic dichorionic pregnancies. Monozygotic twins can be dichorionic (33%), monochorionic diamniotic (66%), or monoamniotic monochorionic (approximately 1%).
- The increased risks associated with multiple gestations are related to chorionicity rather than zygosity and ultrasound plays a critical role in the determination of twin type. Chorionicity is most easily and accurately determined via sonography in the first trimester. Both chorionicity and amnionicity must be established for each embryo.
- The Number of Gestational Sacs Corresponds to Chorionicity. Figure A shows, Early dichorionic twins. Two separate gestational sacs are seen. Figure B shows, Quintuplets following assisted reproduction. Five separate G-Sacs are visible, with a single live embryo within each sac.
- Ultrasonography plays a vital role in the evaluation of multiple gestations, beginning with the first-trimester study. A transvaginal approach is standard for early pregnancy (<8 weeks’ gestational age) 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 visible. The number of sacs will determine the number of chorions. Each sac should be evaluated for the presence of a yolk sac, embryo, and cardiac activity. Careful evaluation of the contents of each sac is critical, to search for more than one yolk sac or embryo.
- In addition to accurately determining chorionicity, first-trimester ultrasound is also highly accurate at dating pregnancy, which is particularly important for multiple gestations. The initial ultrasound report must clearly define the type of gestation, including chorionicity for each embryo, and should provide a single gestational age, as the first sonogram will be used for dating and for directing management of the pregnancy. In patients who have conceived via in vitro fertilization, the embryo transfer date should be used to establish the gestational age. For spontaneous multiples, if the size of the embryos is similar, an average of crown-rump lengths will provide an accurate gestational age. If the embryos are significantly different in size, the pregnancy should be dated based on the crown-rump length of the largest embryo.
- A potential pitfall in the early assessment of multiple gestations is the “appearing twin.” Appearing Twin is defined as undercounting of multiple gestations on early first trimester sonogram. Vanishing twin, as the name depicts, is a condition in which one of a set of twins or multiple embryos dies in utero, disappear, or gets resorbed partially or entirely, with an outcome of a spontaneous reduction of a multi fetal pregnancy to a singleton pregnancy.
- Two distinct gestational sacs within the endometrial cavity indicates dichorionic twins. A single gestational sac containing two yolk sacs is a monochorionic pregnancy, and amnionicity then needs to be determined. Ultrasound is most accurate for assigning chorionicity in pregnancies less than 14 weeks.
- First-Trimester Twins. Image (A) shows Dichorionic diamniotic twins. Two separate gestational sacs, each with embryo and yolk sac. There is thin amnion separated from the chorion in each sac. Image (B) shows Monochorionic diamniotic twins. Single gestational sac with two yolk sacs and two embryos. Image (C) shows Monochorionic monoamniotic twins. Single gestational sac with two separate embryos and a single surrounding amnion (white arrowhead). Image (D) shows Monochorionic monoamniotic conjoined twins. Single gestational sac with a single amnion (white arrowhead), and a single large embryo that contains two heart beats.
- This image shows line diagram of first-trimester pregnancies. Blue, Embryo; brown, amnion; green, chorion; small black, yolk sac.
- As a first step, the placental locations should be determined. Two separate placentas indicate a dichorionic pregnancy. However, approximately 50% of dichorionic placentas can appear fused at sonography. If only a single placenta is seen, the fetal surface of the placenta should be searched for a twin peak or delta sign indicating a dichorionic gestation. Because of the presence of four layers in Dichorionic twins, the membrane is subjectively thicker than Monochorionic twins. When the fetus is large enough to assess anatomy, fetal sex can assist in differentiating twin types. Two different sexes are obviously dichorionic, whereas same-sex twins can be either dichorionic or monochorionic.
- Twin Peak Sign is seen due to a triangular extension of placenta into the intertwin membrane. Two layers of amnion and two layers of chorion form the intertwin membrane of a dichorionic gestation, and proliferating chorion frequently extends between the two chorionic membranes and separates the amnions, thus forming the peak or triangle.
- Right sided image shows T Sign which is seen in MCDA twins. In a monochorionic gestation, the separating membrane is composed of two layers of amnion only, without chorion. The two-amnion membrane meets the placenta/single chorion in a T-shaped manner.
- One important role of the ultrasonologist is to establish which fetus is which, in a way that will allow continuous identification of each fetus. The fetus whose anatomic part is presenting (i.e., is closest to the cervix) is termed as fetus 1 or fetus A. This fetus should remain fetus 1 for the rest of the pregnancy, even if it moves out of the presenting position at some point. 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. In addition to proximity to the cervix, other clues for identifying which fetus is which are placental location, sex, discordant growth, and any potential anomaly.
- Assessment of the amniotic fluid volume is performed for each fetus individually. Fluid volume is assessed either subjectively by an experienced examiner or using the deepest vertical pocket. Deep vertical pocket ranges from 2 cm to 8 cm in a single pocket, where less than 2 cm indicates oligohydramnios and greater than 8 cm indicates polyhydramnios. 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. The abnormal cord insertions include both marginal (11% of twins) and velamentous (6%) insertions and the placental cord insertion of each fetus should be documented.
- These colour doppler images show two types of placental insertion. Image A shows Marginal cord insertion, also known as a 'battledore insertion', is a type of abnormal cord insertion. Image B shows Velamentous cord insertion and is also a type of abnormal cord insertion.
- These are the different types of placental variations.
- Twin pregnancies are known to have higher rates of perinatal morbidity and mortality than singletons and the risk is closely related to chorionicity. The primary complications are premature delivery, intrauterine growth restriction, and intrauterine demise of one or more foetuses.
- Image (D) shows two gestational sacs with separate placentas (RT and LT) with a twin peak sign (arrowhead). Image (E) shows Same patient as D. The twin peak sign (white arrowhead) and a thick intertwin membrane can also be appreciated on the three-dimensional image.
- These images show sonographic findings in Monochorionic Monoamniotic Twins at 26 Weeks. (B) Shows entangled cords in a monoamniotic pair at 22 weeks’ gestational age. (C) Shows same patient as B. Postdelivery at 30 weeks, the two cords are knotted together.
- These images show Triplet Pregnancy Categorization. Image A shows Three separate placentas in a Trichorionic triplet pregnancy , the two anterior placentas appear merged, but a twin peak sign is present. Image B shows both a thin (white arrowhead) and a thick (white arrows) membrane, consistent with Triamniotic dichorionic twins.
- The risk of spontaneous loss of both fetuses is significantly higher in monochorionic twins than dichorionic twins, and in monochorionic twins ; monochorionic monoamniotic twins than in monochorionic diamniotic twins. Twin fetuses are smaller than singletons, and monochorionic twins are more affected.The growth differences are most profound after 30 weeks’ gestation. Altered growth patterns in monochorionic twins are related to unequal placental sharing, whereas a discrepancy in dichorionic twin growth may potentially be due to a more or less favorable uterine implantation site.
- Ultrasound estimation of fetal weight in twins and triplets has been shown to be accurate, and it is an important means of monitoring multiple gestations, as there is an increased risk of fetal loss with discordant fetal weights. Discordant fetal weights – Defined as significant difference (15-25 %)between weights of two fetuses in a twin pregnancy. To be classified as a growth discordance, the estimated fetal weight (EFW) of the smaller twin should fall under the 10th centile
- Single intrauterine fetal death (IUFD) occurs in approximately 4% to 7% of twin pregnancies. Seen more in monochorionic diamniotic as compared to dichorionic twins. Higher losses are also seen with higher degrees of weight discordance between fetuses. In a dichorionic gestation with a single IUFD, there is no significant risk of injury to the surviving fetus, but there is an increased rate of preterm delivery. However, in monochorionic twins with a single demise, risk of severe cerebral injury in the survivor may be as high as 25% to 34%.
- When the first fetus expires, there is a sudden drop in vascular resistance across the placental anastomoses and blood is shunted away from the survivor, with subsequent anemia, hypotension, and hypoperfusion of vital organs. The sonographic manifestations of cerebral ischemia are similar to those seen in premature infants, namely, intracranial haemorrhage, middle cerebral artery infarction, and periventricular white matter injury with subsequent leukomalacia. The combination of twin-twin transfusion syndrome and single IUFD places the survivor at increased risk for cerebral injury.
- Sequelae of Intrauterine Fetal Demise in Monochorionic Twin Gestations. Image (A) shows an Axial image of the fetal head 24 hours after amnioreduction of 1800 mL from the gestational sac of this foetus. There is an echogenic lesion inseparable from the dependent lateral ventricle consistent with intraparenchymal haemorrhage (arrowheads). Image (B) shows same patient as A. Postnatal head ultrasound of the same twin, day of life 1, 48 hours after amnioreduction. There is a large intraparenchymal haemorrhage on the right (arrowheads). Image (C) shows Monochorionic twin at 30 weeks’ gestational age, following an IUFD of its twin 3 weeks ago. There is new ventriculomegaly of the survivor. Image (D) shows same patient as C, 1 week later. Postnatal head ultrasound on day of life 3 shows cystic changes (arrowheads) in a parietal periventricular location consistent with periventricular leukomalacia, the result of the intrauterine fetal demise.
- 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. The anastomoses can be superficial or deep. Three distinct types - arterial/arterial (AA), arterial venous (AV), and venous venous (VV) . AA anastomoses are usually bidirectional and small and are found in 87% of placentas. AV anastomoses are unidirectional, deep, and found in 94% of monochorionic placentas. VV anastomoses are bidirectional, superficial, and found in a minority of placentas
- 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. It is also called as “twin oligohydramnios/polyhydramnios syndrome.” TTTS has same no. of AV anastomosis but more no. of VV anastomosis. AA anastomosis appears to be protective. The syndrome is usually first identified between 16 and 26 weeks’ gestation. Managed by fetoscopic ablation of vascular anastomosis.
- Growth Discrepancy in Twins In Image A , twin labelled with R is larger than twin labelled with L
- 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). The transfusion occurs extremely slowly via tiny unidirectional AV anastomoses, over a long period of time. Although amniotic luid discordance is oten seen as part of the TAPS sequence, the discordance is not as great as seen in TTTS. Diagnosis is done prenatally by color doppler of MCA. 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)
- The twin reversed arterial perfusion (TRAP) sequence is a rare condition that occurs when one twin has an absent or severely malfunctioning heart and there is a large unbalanced AA anastomosis within a monochorionic placenta. Blood flow is directed from the umbilical artery of one twin (pump twin with a normal heart) through the placenta and into the umbilical artery in the second twin, thus reversing flow in that umbilical artery. VV anastomoses allow that blood to then return to the pump twin. There is a high risk of IUFD of the donor twin related to high output cardiac failure and polyhydramnios.
- Image (B) shows normal direction of venous flow in the intrahepatic umbilical vein (into the fetus). Image (C) shows normal direction of arterial low in the umbilical artery (out of the fetus).
- This image shows abnormal reversed arterial flow (into the fetus) in the umbilical artery of twin 2.