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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