Multiple Gestations

Dr. Syed Shoaib Muhammad

Definition:

Presence of more than one fetus in the gravid uterus-Twins (two babies)

-Monozygotic(Division of 1 ova fertilized by the same sperm)

-Dizygotic(Fertilization of 2 ova by 2 sperm)

-Triplets (three babies)

-Quadruplets (four babies)

Incidence

• Twins - 1 in 85 births

• Chile : 1 in 51

• African : 1 in 70

• Japanese : 1 in 150

• Chinese : 1 in 300

• Triplets are about 1 in 7,629 births

• Quadruplets are about 1 in 670,734

births

• Twins : 1 in 80

• Triplets : 1 in 80 × 80

• Quadruplets : 1 in 80 × 80 × 80….

• Gemellology : Study of twins

Hellin’s Rule

Types of Twins:

DIZYGOTIC

MONOZYGOTIC

DIZYGOTIC or FRATERNAL TWINS

Always Dichorionic & Diamnionic

Amnion

Amnion

2 Chorions

Dizygotic Twins

Fertilizations of 2 ova by different spermatozoa.

Each twin has its own placenta, chorions , amnion.

Hence always dichorionic, diamnionic.

Factors Affecting Dizygotic TwinningEthnic group

Increasing maternal age

Increasing parity.

Family history of twinning.

Ovulation induction

MONOZYGOTIC or IDENTICAL Twins

MONOZYGOTIC or IDENTICAL Twins

Monozygotic Twins

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

ULTRASOUND DETERMINATION OF CHORIONICITY

Number of sacs

Placenta

Sex

Intertwin membrane

Lambda sign & T sign

Ideal time for assessing of chorionicity is before 14 weeks

DIZYGOTIC

LAMBDA SIGN

MONOCHORIONIC & DIAMNIONIC T

SIGN

Maternal Complications

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.

ANTEPARTUM HEMORRHAGE – Placenta praevia , Abruptio placenta.

Fetal Complications

Antepartum Intrapartum

1. Prematurity1. Premature Rupture of the Membranes

2. Intrauterine Growth Restriction 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

I. PrematuritySingle most important cause of perinatal mortality and morbidity.

Fetal Complications

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.

II. IUGR

III. Single Fetal Demise

Monochorionic

Death of one twin

Shift of blood Normal

twin

25% risk of co-twin death /25% risk of neurological damage in surviving twin

IV. TWIN-TWIN TRANSFUSION SYNDROME

Occurs in monochorionic placentation due to AV anastomoses with resultant flow in one direction.

Arterio venous anastomoses with net flow in one direction..

Donor(arterial side)

Recipient

•Severe IUGR•poor renal perfusion•Anuria•Severe Oligohydramnios

•Hypervolemia•Polyuria with polyhydramnios•Hydrops…death

V. 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 TWINWhen 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.

VI. Congenital anomalies

• Unique to twins – conjoined twins , Acardiac fetus• Non specific but common in twins – CHD ,

Anencephaly• Postural deformities – Talipes & Congenital

dislocation of Hip

STRUCTURAL MALFORMATIONS

• Dizygotic – independent risk, but both will not be involved

• Monozygotic – same risk as that of singleton, both affected

• Down’s syndrome

CHROMOSOMAL ANOMALIES

VII. Conjoined Twins

Always monozygotic

Incomplete division occurring after 13 days.

Very rare

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

THORACOPAGUS ISCHIOPAGUSCRANIOPAGUS

RACHYPAGUSPYOPAGUSOMPHALOPAGUS

References: