multiple pregnancy - diagnosis ,clinical features & complications
TRANSCRIPT
MULTIPLE PREGNANCY Hari Dev 2008 MBBS
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. ZYGOSITY
Dizygotic Twins
Monozygotic Twins
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.
DIZYGOTIC TWINS/ BINOVULAR
2.MONOZYGOTIC / BINOVULAR/ IDENTICAL
25% Result from splitting of a single fertilized ovum
Always same sex and look alike. [ IDENTICAL ]
Rate of monozygotic twinning is relatively constant , not affected by any factors.
True etiology unknown.
Type of placentation is determined by the time of splitting
MONOZYGOTIC TWINS
MONOZYGOTIC / BINOVULAR/ IDENTICAL
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 Dichorionic
Placenta Single Double
Fetal Sex -------- Discordance
Membrane <2 mm >2 mm
No: of layers in membrane
2 layers 4 layers
Twin peak sign Absent Present
Maternal Complications
Antepartum Intrapartum1.Hyperemesis 1.Dysfunctional labour
2.Hydramnios 2.Malpresentation
3.Pre-eclampsia 3.Operative delivery
4.Pressure symptoms 4.Postpartum hemorrhage
5.Anaemia 5.Retained Placenta
6.Antepartum hemorrhage
6.Premature separation of placenta
Maternal Complications - AntepartumHyperemesis – 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 Complications
Antepartum Intrapartum
1.Prematurity 1.PROM
2.IUGR 2.Cord Prolapse
3.Single fetal demise 3.Abruption in second twin
4.Twin to Twin transfusion syndrome
4.Interlocking (rare)
5.Vanishing Twin/abortion
6.Cong.anomalies
7.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. IUGR
Can affect one or both fetuses.
Monochorionic > Dichorionic.
UPTO 30-32 Weeks twins grow with same velocity , after that reduction in abdominal circumference.
Poor growth – poor placentation , unequal placental sharing, fetal anomalies.
3. SINGLE FETAL DEMISE
Death of one twin
NEUROLOGICAL DAMAGE
in surviving TWIN
3. SINGLE FETAL DEMISE
Monochorionic - 25% risk of twin death, 25% risk of neurological damage in surviving twin.
• Dilemma exists whether to deliver early or not• Terminated as soon as other twin is capable of extra uterine survival
Dichorionic – no such risk
• Conservative management
4.Monochorionic Monoamniotic twinning
Seen in less than 1% of all twin pregnancies
Late intrauterine death due to cord entanglement.
Best diagnosed in 1st trimester – absence of intervening membrane.
Colour doppler – cord entaglement
Fetal loss – 50-70%
Hence elective CS at 36 weeks.
5. Twin – twin Transfusion Syndrome [ TTS]
Occurs in monochorionic placentation due to AV anastomoses with resultant flow in one direction.
5. Twin – twin Transfusion Syndrome [ TTS]
Can be acute or chronic
Can be recognised in utero by ULTRASOUND
Main cause of perinatal loss in chronic TTS is preterm labour secondary to severe polyhydramnios.
Prognosis for both fetuses is not good.
Ultrasound in TTS – STUCK TWIN SIGN
• 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
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Diagnosis made after delivery
No effect on mother or the viable fetus.
7. Congenital Anomalies
STRUCTURAL MALFORMATIONS
• Unique to twins – conjoined twins , Acardiac fetus• Non specific but common in twins – CHD , Anencephaly• Postural deformities – Talipes & Congenital dislocation of Hip
CHROMOSOMAL 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
DICHORI
ONIC PREGNANCY
If one
fetus is
abnormal
Selective
feticide
using KCl
Anomalies Unique to twins..
Conjoined TwinsAlways monozygotic
Incomplete division occuring after 13 days.
Very rare
Thoraco pagus, craniopagus, omphalopagus, pyopagus, ischiopagus..
Prenatal diagnosis important – for termination , for planning operation
Severe cases detected early – Termination
Surgical separation only in some cases – sharing of brain and heart – unsuccessful operation
Caesarean preferred
THORACOPAGUSISCHIOPAGUSCRANIOPAGUS
RACHYPAGUSPYOPAGUSOMPHALOPAGUS
Acardiac Foetus
Very rare
Bizarre form of monochorionic twinning
One fetus is normal
The other twin is severely malformed – no heart , absent development of upper part of body
MECHANISMPUMP TWIN ACARDIAC TWIN
Twin Reversed Arterial Perfusion Sequence [ TRAP]
•Pump twin – high output cardiac failure, hydrops, poly hydramnios and death
•Overall perinatal mortality of pump twin is 50%
PUMP TWIN ACARDIAC TWIN
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