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Multiple Gestations

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Multiple Gestations A Few Too Many Sonography of Multiple Gestations Ivana M Vettraino, MD, MBA Maternal Fetal Medicine Director, Perinatal Center, Genetics and Outreach Mercy – St Louis Disclosures Speakers bureau March of Dimes Hologic, Inc Trainer Nexplanon I will not be discussing any of these organizations or products in this presentation 2 Objectives Define and describe the categories of multiple gestations Describe the keys to ultrasound assessment of multiple gestation Describe sonographic complications of twin gestation and other higher order multiples Introduce management of twin gestation in the prenatal period Introduction Account for 3 % of all pregnancies Incidence human pregnancies Approximately 1 in 90 births Rate varies from country to country Highest numbers - Nigeria (45 twins per 1000 live births) Lowest in Japan (4 twins per 1000 live births) United States (2016) – 33.4 twins per 1000 live births Vary by ethnic group Hispanic women 19.5 per 1000 births Non-Hispanic black women 30.0 per 1000 births Non-Hispanic white women 28.8 per 1000 births Multiple Gestation Overall rise in multiple gestations Older age at childbearing 1/3 Increasing use of infertility therapies 2/3 Triplet Data Twinning Monozygotic twins (“identical”) Develop from a single fertilized ovum Have same genetic material Rate is constant worldwide 3.5 to 4 per 1000 births 30 percent of twins Dizygotic twins (“fraternal”) Develop from more than one fertilized ovum Genetically similar as any full siblings Rate varies by ethnic background, maternal age, parity, family history, use of ART 70 percent of twins Placentation Splitting within first 2 days after fertilization Separate chorion and amnion - Dichorionic/diamniotic Different placentas that can be separate or fused 30% of monozygotic twins Splitting during days 3-8 after fertilization One chorion and two amnions - Monochorionic/diamniotic 70% of monozygotic twins Can have vascular communications between the 2 circulations and develop twin-to-twin transfusion syndrome Splitting during days 9-12 after fertilization One chorion and one amnion - Monochorionic/monoamniotic 1% of monozygotic twins Placentation Conjoined twins Incomplete embryonic division Splitting 13 to 15 days after conception 1 in 50,000 births Classified according to site of union Thoracopagus - Chest (40%) Xiphopagus/omphalopagus - Abdomen (34%) Pygopagus - Buttocks (18%) Ischiopagus - Ischium (6%) Craniopagus - Head (2%) Placentation Ascertainment of chorionicity extremely important Monochorionic twins account for 20% to 33% of twin gestations Relative risk of perinatal mortality of 2.5 Neurologic morbidity 4 to 5 times dichorionic twins 25 to 30 times singleton pregnancies Optimal time to ascertain is in the 1st trimester Placentation Diagnosis At or after 14 weeks Discordance of fetal gender by sonogram Positive predictive value approaches 100% Only 55% of all twins discordant for gender Rarely, post-zygotic disjunction can result in a female fetus with 45,X karyotype and a normal male co-twin Two separate placental masses Only one-third of twin gestations Beware the succenturiate placental lobe Thickness of the intertwin membrane 2 mm or greater had 90% sensitivity and 76% specificity Placentation Placentation Placentation The Yolk Sacs Two yolk sacs Diamniotic twins One yolk sac Follow-up sonogram should be suggested as could be monoamniotic or diamniotic Placentation 35% of twins divide between 2-8 cell stage Two babies, two amnions, and two chorions, and one fused or two separate placentas Cannot tell difference between these twins unless genetic testing is done If two placentas are present – twin could still be identical Placentation Ascertainment of chorionicity extremely important Monochorionic pairs account for 20% to 33% of twin gestations Relative risk of perinatal mortality of 2.5 Optimal time to ascertain is in the 1st trimester Dating the Pregnancy Optimally assigned in 1st trimester using CRL Twins conceived by ART Embryo age Date of transfer Discrepancy between CRLs or dates by LMP Use size of larger twin Decreases risk of missing fetal growth restriction Complications - Antepartum Miscarriage Premature labor Congenital malformations Higher incidence of IUGR Higher incidence of maternal anemia Increased risk for PROM Twin-to-twin transfusion syndrome Pregnancy induced hypertension Hydramnios Complications - Antepartum “Vanishing Twin” Miscarriage more common in multifetal pregnancies One twin lost prior to 2nd trimester in 10 to 40 percent of pregnancies Incidence high in pregnancies conceived by assisted reproductive technologies (ART) Monochorionic at greater risk than dichorionic The more fetuses – the more common Complications - Antepartum Spontaneous reduction of one or more gestational sac before the 12th week 36% of twin 53% of triplet 65% of quadruplet pregnancies Complications - Antepartum Death of one twin in utero 2% to 7% in spontaneously conceived pregnancies 25% in gestations conceived by ART After the 1st trimester Intrauterine growth restriction Preterm labor Perinatal mortality Complications - Antepartum Premature delivery Duration of pregnancy decreases with increasing fetal number Indicated preterm deliveries far more common that those by spontaneous preterm labor Preeclampsia Discordant growth Worsening maternal medical condition Complications - Antepartum Average length of pregnancy Singleton 39-41 weeks Twins 35-37 weeks Triplets 33- 35 weeks Quadruplets 29 -31 weeks Complications - Antepartum Cervical length assessments No longer recommended Don’t place a cerclage in women with short cervix who are pregnant with twins Does not reduce actual rate of preterm births Complications - Antepartum Congenital malformations Twice as high as singleton Monochorionic twins approximately twice dichorionic twins Greater risk in pregnancies conceived by ART Can be discordant One twin may be normal appearing and the other anomalous Images Twin Gestation with Co-existent Normal Fetus and Complete Hydatidiform Mole Images Molar degeneration Normal appearing placenta Images “Twin Molar Pregnancy” Prevalence 1 in 22,000 to 1 in 100,000 pregnancies Must be differentiated from partial molar pregnancy Presence of triploid fetus with multiple anomalies and early onset severe fetal growth restriction Continuation can place mother at risk for persistent trophoblastic disease which can be fatal 1/3 of pregnancies complicated by vaginal bleeding and severe preeclampsia Live birth in approximately 35 % of pregnancies Images 10 5/7 weeks’ gestation Images Images Monochorionic diamniotic 14 4/7 weeks’ gestation Images Nuchal hygroma Skin edema Complications - Antepartum Higher incidence of IUGR Prevalence of 26% in dichorionic and 46% in monochorionic twins Monochorionic twins Disproportionate placental sharing 15 percent of pregnancies Associated with 5 to 10 percent of the perinatal mortality Management options depending on gestational age Selective termination Strict antepartum surveillance Consideration of early delivery Complications Monochorionic Twins Twin to twin transfusion syndrome (TTTS) Selective intrauterine fetal growth restriction (sIUGR) Discordant fetal growth Twin anemia polycythemia sequence (TAPS) Twin reverse arterial perfusion (TRAP) Monochorionic monoamniotic twinning Complications - TTTS Complicates 10 to 15 % of monochorionic twins Usually presents in the second trimester (16 to 26 weeks’) 1/3 of perinatal deaths in monochorionic pregnancies Ablation of placental anastomoses prior to 26 weeks’ gestation Perinatal survival 50 to 70 percent Early Sonographic Findings First Trimester CRL discordance Nuchal translucency Greater than the 95th percentile Discordance of greater than 20 percent between each fetus Reversal or absence of A wave of the ductus venosus Subjectively discordant fluid volumes TTTS – Staging Criteria Images Images MVP = 8.02 cm MVP = 1.89 cm Images Demise of One Fetus Complications – sIUGR Early 10 percent of monochorionic twins Discordant growth Mean EFW less than 10th percentile in one fetus Mean EFW discordance greater than or equal to 25% Calculation (larger weight – smaller weight)/larger weight Complications – sIUGR Late 5 percent of monochorionic twins Discordant growth Mean EFW less than 10th percentile in one fetus Progressive discordance in the 3rd trimester Outcomes usually good unlike early onset sIUGR Categories SIUGR Type Clinical Features Timing of Delivery • Good prognosis with mild 1 growth discordance 34-35 weeks’ gestation Normal umbilical artery • Low risk of IUFD Doppler – Diastolic flow • Low risk brain injury co-twin 2 • High risk for progression 26-32 weeks’ gestation Reversed or absent end and IUFD of IUGR twin diastolic flow in the • Low risk brain injury co-twin umbilical artery Doppler • Low risk of hypoxic 3 deterioration of IUGR twin Intermittent reversed or • 10 to 15 % risk unexpected 30 weeks’ gestation absent end diastolic flow demise IUGR twin in the umbilical artery • 10 to 15 % risk brain injury Doppler co-twin Ultrasound Obstet Gynecol 2007;30:28-34 sIUGR Management Considerations Fetal Diagn Ther 2014 sIUGR Management Type 1 Weekly to twice weekly sonograms to assess fetal growth and progression to Type 2 or 3 Type 2 and Type 3 May necessitate consideration for fetal therapy Selective cord occlusion Improve outcome for normally growing twin by stopping
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