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: