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									Twins & Higher
 Dr. Ahmed Al Harbi
MULTIPLE PREGANCIES consists of two or
more fetuses .

TWINS make up the vast majority (97-98%)
of multiple gestations.

Pregnancies with three or more fetuses are
referred to as ‘higher multiples’.
In the UK, twins currently account for
approximately 1.5% of all pregnancies.

Higher multiples occur in 1 in 2,500
Risk factors for multiple gestation include:

   1. Reproduction Techniques
         (Both ovulation and in-vitro fertilization or IVF)
   2. Increasing maternal age
   3. High parity
   4. Black Race
   5. Maternal family history
Classification of multiple pregnancy
    Number of fetuses: twins, quadruplets, etc.
    Number of fertilized eggs: zygosity
    Number of placentas: chorionicity

Non identical or fraternal twins are dizygotic,
having resulted from the fertilization of two
separate eggs.

Two functionally separate placentas (dichorionic)
They always have separate amniotic cavities
(diamniotic) and the two cavities.

The fetuses can be either same-sex or different-

Identical twins are monozygotic- they arise from
fertilization of a single egg and are always same-
sex pairings.

Monochorionic twins may occasionally share a
single sac (monoamniotic).
Key Points
Not all dichorionic pregnancies are

All monochorionic pregnancies are
Dizygotic twins may arise spontaneously
from the release of two eggs at ovulation

The tendency to release more than one egg
can be familial or racial in origin and
increases with maternal age.

Monozygotic twins arise from a single
fertilized ovum that splits into two identical
The type of monozygotic twin depends on how
long after conception the split occurs.

When the splits occurs within 3 days of
conception, two placentas and two amniotic
cavities result, giving rise to a dichorionic
diamniotic (DCDA) pregnancy.

When splitting occurs between days 4 and 8,
only the chorion has differentiated and a
monochorionic diamniotic (MCDA)
pregnancy results.
Later splitting after the amnion has
differentiated leads to both twins developing
in a single amniotic cavity, a monochorionic
monoamniotic (MCMA) pregnancy.

If splitting is delayed beyond day 12, the
embryonic disc has also formed, and
conjoined or ‘Siamese’ twins will result.

It is not influenced by race, family history or
Other Physiology
 All the physiological changes of pregnancy
 (increased cardiac output, volume
 expansion, relative haemodilution,
 diaphragmic splinting, weight gain, lordosis,
 etc.) are exagerated in multiple gestations.
 Monochorionic placentas have the unique
 ability to develop vascular connections
 between the two fetal circulations.

 These anastomoses carry the potential for
Relevant To Twin
A. Miscarriage &
           Severe Preterm Delivery
    Therefore about half of all twins deliver preterm.
    As most babies born from 32 weeks onwards do very
    well, births at 34 or 35 weeks carry little clinical
    In contrast, almost all babies born at 23 weeks or
    less die, with rates of mortality and handicap
    steadily falling between 24 and 31 weeks.
Dichorionic / Monochorionic Differences

                       Singleto Dichorion   Monochorio
                        n (%)    ic (%)      nic (%)

Miscarriage at 12-23      1         2           12
Delivery at 24-32         1         5           10
Growth Restriction        5        10           20

Fetal Defects             1         2           8
B. Perinatal Mortality In Twins
     The overall perinatal mortality rate for twins is around
     six times higher than for singletons.
     The biggest contributor to this high rate is
     complications related to preterm birth.

Dichorionic / Monochorionic Differences
     As preterm delivery is most common in monochorionic
     twins, their perinatal mortality secondary to this is
     twice as high as in dischorionic twins.
C. Death of one fetus in a twin pregnancy
     After the 1st trimester, the intrauterine death of one fetus in a
     twin pregnancy may be associated with a poor outcome for the
     remaining co-twin.

Dichorionic / Monochorionic Differences
     Acute hypotensive episodes, secondary to placental vascular
     anastomoses between the two fetuses, result in
     haemodynamic volume shifts from the live to the dead fetus.
     Death or handicap of the co-twin occurs in up to 25% of cases.
D. Intrauterine Growth Restriction

     The risk of poor growth is higher in each individual twin
     alone and substantially raised in the pregnancy.

Dichorionic / Monochorionic Differences
     The chance of poor fetal growth for monochorionic
     twins is almost double that for dichorionic twins.
E. Fetal abnormalities

     Compared to singletons, twins the risk of the birth of a
     baby with an anomaly.

Dichorionic / Monochorionic Differences
     Each fetus of a dichorionic twin pregnancy has a risk of
     structural anomalies, such as spina bifida.
     Anencephaly is a good example of a lethal abnormality
     that can threaten the survival of the normal twin.
F. Complications Unique To
           Monochorionic Twinning
   Twin-to-twin transfusion syndrome (TTTS).

   The donor fetus suffers from both hypovolaema due to
   blood loss and hypoxia due to placental insufficiency,
   and may become growth-restricted and oliguric.

   This fetus develops oligohydramnios.

   The recipient fetus becomes hypervolaemic, leading to
   polyuria and polyhydramnios.
There is a risk of myocardial damage and high output
cardiac failure.

Severe disease may become apparent at 18-24 weeks
of pregnancy.

The mother often complains of a sudden increase in
abdominal girth associated with extreme discomfort.
•   The differential diagnosis of a multiple
    gestation includes all the other causes of a
    ‘large for dates’ uterus: polyhydramnios,
    uterine fibroids, urinary retention and ovarian
    masses .
•   Routine antenatal care for all women involves screening for

    hypertension and gestational diabetes.

•   These conditions occur more frequently in twin pregnancies and

    there is also a higher risk of other problems (such as antepartum

    haemorrhage and thromboembolic disease).
A. Determination of chorionicity

B. Screening for fetal abnormalities
    The optimal method of screening twins is by

    The measurement of nuchal translucency at 12
     weeks gestation allows each fetus to have an
     individualized assessment of risk.

    Both amniocentesis and chorion villus sampling
C. Monitoring fetal growth & well-being
    Monitoring for fetal growth and well-being in twins is
     principally by ultrasound scan.
    Each assessment should include fetal measurement,
     fetal activity, fetal lies and amniotic fluid volumes.
    In monochorionic twins, features of TTTS should be
     sought, including discordances between fetal size, fetal
     activity, bladder volumes, amniotic fluid volumes and
     cardiac size.
    Doppler assessment of the fetal circulations and
     cardiotocography (CTG).
D. Threatened preterm labour

    Antenatal strategies in those identified as at high risk
     may include screening for bacterial vaginosis (treatment
     may eliminate a co-factor for spontaneous preterm
     labour), screening for group B Streptococcus (GBS;
     intrapartum antibiotics reduce neonatal infection),
     maternal steroid therapy to enhance fetal lung
    Once preterm is diagnosed, neonatal unit staff must be
     promptly involved.

    The use of tocolytic drugs in this situation, particularly
     the beta-agonists, carries risks of serious maternal

D. Multiple pregnancy support groups
   A twin CTG machine should be used for fetal monitoring
   and a portable ultrasound machine should be available
   during delivery.

   A standard oxytocin solution for augmentation should
   be prepared, run through an intravenous giving-set and
   clearly labelled ‘for augmentation’, for use for delivery
   of the second twin, if required.
A second high-dose oxytocin infusion should also be
available for the management of postpartum

It is essential that two neonatal resuscitation trolleys, two
obstretricians and two paediatricians are available and
that the special care baby unit and anaesthetist are
informed well in advance of the delivery.
A. Analgesia during labour
  •   Epidural analgesia is recommended.

B. Fetal well-being in labour
  •   Fetal heart rate monitoring should be continuous throughout
      labour, ideally using a speciallized twin monitor.
  •   An abnormal fetal heart rate pattern in twin I may be assessed
      using fetal scalp sampling, as for a singleton pregnancy.
  •   However, a non-reassuring pattern in twin 2 will usually
      necessitate delivery by Caesarean section.
  •   The condition of twin 1, as acute complications such as cord
      prolapse and placental separation are well recognized.
C. Vaginal delivery of vertex-vertex
  •    Delivery of the first twin is undertaken in the usual manner
      and thereafter the majority of second twins will be delivered
      within 15 minutes.
  •   After the delivery of the first twin, abdominal palpitation
      should be performed to assess the lie of the second twin.
  •   It is helpful to use ultrasound for confirmation, which is also
      useful for checking the fetal heart rate.
  •   If the lie is longitudinal with a cephalic presentation, one
      should wait until the head is descending and then perform
      amniotomy with a contraction.
  •   If contractions do not ensue within 5-10 minutes after delivery
      of the first twin, an oxytocin infusion should be started.
  •   If an assisted delivery becomes necessary, the vacuum
      extractor has a number of advantages.

C. Delivery of vertex-non-vertex

D. Non-vertex first twin
  •   When twin 1 presentation as a breech, clinicians usually
      recommend delivery by elective Caesarean section.
  •   Other factors include dwindling experience of breech delivery
      and the rarely seen phenomenon of ‘locked twins’.
E. Preterm twins
 • Even in low-birth-weight twin gestations, the method of delivery
   in relation to fetal presentation will have little or no effect on
   neonatal mortality and subsequent neonatal development
 • No significant differences in perinatal outcome exist when
   comparing breech-extracted second twins to those delivered by
   Caesarean section.
Requirements for twin delivery
 •   Large delivery room
 •   Operating theatre and staff ready
 •   Anaesthetist present
 •   Senior obstetrician present
 •   At least two midwives present
 •   Twin resuscitaires
 •   Ventous/forceps to hand
 •   Blood grouped and saved
 •   Intravenous access
 •   Neonatologists present
 •   Pre-mixed oxytocin infusion ready

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