MULTIPLE PREGNANCY• Presence of more than one fetus in the gravid uterus• 1% of all pregnancies• Hellin’s Rule – Twins : 1 in 80 – Triplets : 1 in 80 × 80 – Quadruplets : 1 in 80 × 80 × 80….• Gemellology : Study of twins
• ZYGOSITY - Refers to the Type of Conception. - only determined by DNA testing• CHORIONICITY - Type of Placentation - prenatally by ultrasound - postnatally by examining membranes.
1.DIZYGOTIC TWINS/ BINOVULAR75%Fertilisation of 2 ova by different spermatozoa.Each twin has its own placenta, chorion , amnion.Hence always dichorionic, diamniotic.Factors affecting - ethnic group - increasing maternal age - increasing parity - Family history of twinning - ovulation induction with clomiphene citrate/gonadotrophins resulting in multiple ovulation.
2.MONOZYGOTIC / BINOVULAR/ IDENTICAL25%Result from splitting of a single fertilized ovumAlways same sex and look alike. [ IDENTICAL ]Rate of monozygotic twinning is relatively constant , not affectedby any factors.True etiology unknown.Type of placentation is determined by the time of splitting
2.CHORIONICITY• Type of Placentation• Postnatally- Examination of Membranes• Prenatally- By Ultrasound• Ideal time for assesment is before 14 weeks
Which is more important –zygosity or chorionicity??
CHORIONICITY………Why????• Dichorionic twins can be either mono/dizygotic.• Dichorionic twins develop as two distinct organs. – so no risk.
CHORIONICITY………Why????• Monochorionic twins have increased vascular anastomoses between the two circulation – so high risk!!
Ultrasound Determination of Chorionicity• Number of sacs. [ before 10 weeks ] 2 sacs – dichorionic Single sac - monochorionic• Placenta• Sex• Intertwin membrane thicker and more echogenic in dichorionic.
• Twin peak / Lambda sign - characteristic of dichorionic pregnancies - chorionic tissue between 2 layers of intertwin membrane at the placental origin• T Sign – in monochorionic , no chorionic tissue• If no membrane is seen in between – monochorionic monoaniotic
Ultrasound differentiation of chorionicity Criterion Monochorionic DichorionicPlacenta Single DoubleFetal Sex -------- DiscordanceMembrane <2 mm >2 mmNo: of layers in 2 layers 4 layersmembraneTwin peak sign Absent Present
Maternal Complications - Antepartum Hyperemesis – increased β- hCG Hydramnios – monoamniotic pregnancies, Twin transfusion syndrome, major cause of prematurity Pre- eclampsia – 3 times commoner compared to singleton Pressure symptoms Anaemia – increased plasma volume expansion , fetoplacental demand for iron increased. APH – Placenta praevia , Abruptio placenta.
Fetal ComplicationsAntepartum Intrapartum1.Prematurity 1.PROM2.IUGR 2.Cord Prolapse3.Single fetal demise 3.Abruption in second twin4.Twin to Twin transfusion 4.Interlocking (rare)syndrome5.Vanishing Twin/abortion6.Cong.anomalies7.Conjoined twins
FETAL COMPLICATIONS Perinatal mortality: 6 times Morbidity: 2- 3 times Mono chorionic - morbidity/mortality twice as that of dichorionic. - additional risk from TTS Monoamniotic twins - 50% mortality. Main cause of adverse outcome is 1. Prematurity 2. IUGR Cerebral palsy, neurodevelopmental impairment, lower IQ scores. Monochorionic twins: 1. TTTS 2 .Monoamniotic twinning 3. Conjoined twinning 4. Acardiac fetus
1. Prematurity• Single most important cause of perinatal mortality and morbidity.• Ensure delivery in a tertiary care centre.!!
2. IUGRCan affect one or both fetuses.Monochorionic > Dichorionic.UPTO 30-32 Weeks twins grow with same velocity , afterthat reduction in abdominal circumference.Poor growth – poor placentation , unequal placentalsharing, fetal anomalies.
3. SINGLE FETAL DEMISEDeath of one twin NEUROLOGICAL DAMAGE in surviving TWIN Sudden acute shift of blood from surviving twin to dead fetus
3. SINGLE FETAL DEMISEMonochorionic - 25% risk of twin death, 25% risk ofneurological damage in surviving twin.• Dilemma exists whether to deliver early or not• Terminated as soon as other twin is capable of extra uterine survivalDichorionic – no such risk• Conservative management
4.Monochorionic Monoamniotic twinningSeen in less than 1% of all twin pregnanciesLate intrauterine death due to cord entanglement.Best diagnosed in 1st trimester – absence of intervening membrane.Colour doppler – cord entaglementFetal loss – 50-70%Hence elective CS at 36 weeks.
5. Twin – twin Transfusion Syndrome [ TTS]Occurs in monochorionic placentation due toAV anastomoses with resultant flow in onedirection.
• Management after delivery – Exchange transfusion• Chronic TTS – Serial amnio reduction – - Reduces preterm labour - Reduce hydrostatic pressure – - improves circulation and urine production.• Fetoscopic laser ablation of anastomoses
• Acute TTS can occur in 3rd trimester or in labour – sudden death of one twin• Overall mortality is 70%• High incidence of CP and neurological abnormalities in survivors.
6. Vanishing Twin & Abortion Incidence of abortion more in multiple pregnancy Spontaneous cessation of cardiac activity in a previously viable fetus of a multiple gestation. – VANISHING TWIN When fetal death occur after the first trimester, results in a thin parchment – like body called FETUS PAPYRACEOUS Diagnosis made after delivery No effect on mother or the viable fetus.
7. Congenital AnomaliesSTRUCTURAL MALFORMATIONS• Unique to twins – conjoined twins , Acardiac fetus• Non specific but common in twins – CHD , Anencephaly• Postural deformities – Talipes & Congenital dislocation of HipCHROMOSOMAL ANOMALIES• Dizygotic – independent risk, but both will not be involved• Monozygotic – same risk as that of singleton, both affected• Down’s syndrome
Nuchal Translucency Mid Trimester Amniocentesis is the gold standard
Management of Anomalies SelectiveDICHORIONIC If one fetus is feticide usingPREGNANCY abnormal KCl
Conjoined TwinsAlways monozygoticIncomplete division occuring after 13 days.Very rareThoraco pagus, craniopagus, omphalopagus, pyopagus, ischiopagus..Prenatal diagnosis important – for termination , for planning operationSevere cases detected early – TerminationSurgical separation only in some cases – sharing of brain and heart – unsuccessful operationCaesarean preferred