Multiple Pregnancy Diagnosis and Clinical Management

Definition

Multiple pregnancy- occurs when more than one fetus simultaneously develop in the uterus.

Twin pregnancy- Is the simultaneous development of two fetuses. Although rare, Development of three fetus (triplets), four (quadruplet), five (quintuplets), six (sextuplets) may also occur.

Twin pregnancy is the commonest variety of multiple pregnancy.

It is of two types:

1. Dizygotic twins (80%), which results from fertilization of two ova leading to fraternal twin.
2. Monozygotic twins (20%), which results from fertilization of one ova leading to identical twin.

Monozygotic twins - 4/1000 births

Dizygotic twins – 2/3rds of all twins, race, age, assisted conception

Triplets – 1 in 7000 to 10,000 births

Quadruplets – 1 in 600,000 births

Almost every maternal and obstetric problem occurs more frequently in multiple Pregnancy

• Perinatal mortality rate in twins is 5 times higher and in triplets 10 times higher than in singletons

Incidence of 42 per 1000 deliveries have been reported in western Nigeria

Igbo ora has the highest birth rates of twins in the world

In Ilorin 37.60 per 1000 deliveries was reported in UITH

Zygosity and Chorionicity

• Zygosity refers to the type of conception
• Chorionicity denotes the type of placentation
• Chorionicity rather than zygosity determines outcome

1. Increasing maternal age (30-35yrs)
2. Increasing parity (5 gravida onwards)
3. Nutritional factors
4. Pituitary gonadotropin
5. Infertility therapy
6. Assisted reproductive therapy
7. Genetic, hereditary- for dizygotic twins, usually a daughter inheriting it from the mother.
8. Race, black>whites

Most common represents 2/3 of cases.

Fertilization of more than one egg by more than one sperm.

Non-identical, may be of different sex.

Two chorion and two amnion.

Placenta may be separate or fused.

Genesis of dizygotic twins

Results from Fertilization of two ova, mostly likely rupture from two distinct graafian follicles usually of the same or one from each ovary, by two sperms during single ovarian cycle.

There are two placentae either completely separated or more commonly fused at the margin

Each fetus is surrounded by a separate amnion and chorion.

Sex of the fetus may differ.

Genetic features (blood group, finger prints) also differs.

Constant incidence of 1:250 births.

Not affected by heredity.

Not related to induction of ovulation.

Constitutes 1/3 of twins.

70% are diamniotic monochorionic.

30% are diamniotic dichorionic.

Results from division of fertilized egg:

• 0-72 H. Diamniotic dichorionic.
• 4-8 days Diamniotic monochorionic.
• 9-12 days Monoamniotic
• >12 days Conjoined twins.

Genesis of monozygotic

The twinning may occur at different periods after fertilization.

If the division takes place within 72hours after fertilization (prior to morula stage) resulting embryos will have two separate placenta, chorion, and amnions (diamnioticdichorionic)

If the division takes place between 4th and 8th day after the formation of inner cell mass when chorion has already developed - diamniotic monochorionic twins develop.

If division occurs after 8th day of fertilization when amniotic cavity has already formed (monoamniotic monochorionic twins)

Division after two weeks of developmentt of embryonic disc results in the formation of conjoined twin.

History

• History of ovulation inducing drugs
• Family history of twinning (maternal side)

Symptoms

Minor ailments of normal pregnancy are often exaggerated. Some of the symptoms are related to the undue enlargement of the uterus:

• Increased nausea and vomiting in early months
• Cardiorespiratory embarrassment – palpitations, shortness of breath.
• Tendency of swelling of legs, varicose veins and hemorrhoids is greater.
• Unusual rate of abdominal enlargement and excessive fetal movement may be noticed.

General examination:

• Increased prevalence of anemia
• Unusual weight gain not explained by preeclampsia or obesity
• Evidence of preeclampsia is a common association

Abdominal examination

• Elongated shape of normal pregnant uterus is changed to a more barrel shape and the abdomen is unduly enlarged
• Height of the uterus is more than gestation age.
• Fetal bulk seems disproportionally larger in relation to the size of fetal head.
• Palpation of too many fetal parts
• Finding two fetal heads.
• Two distinct fetal heart sounds at separate spots with a silent area in between.

Investigations

• Sonography
• Separate gestational sacs can be identified early in twin pregnancy
• Dichorionic diamniotic twins have a membrane between the twins, with a lambda sign or twin peak sign. The lambda sign refers to the triangular appearance where the membrane between the twins meet the chorion, as the chorion blends partially into the membrane.
• Monochorionic diamniotic twins have a membrane between the twins, with a T sign. The T sign refers to where the membrane between the twins abruptly meet the chorion, giving a T appearance.
• Monochorionic monoamniotic twins have no membrane separating the two.
• Two fetal heads or two abdomens should be seen in the same plane, to avoid scanning the same fetus twice and interpreting it as twins.
• Radiologic Examination
• Not useful and may lead to an incorrect diagnosis
• Biochemical Test
• Amounts of chorionic gonadotropin in plasma and in urine, on average, are higher than those found with a singleton pregnancy, but not so high as to allow a definite diagnosis of multiple fetuses

DDx. of multiple fetus

In women with a uterus that appears large for gestational age, the following possibilities are considered:

• Elevation of the uterus by a distended bladder
• Inaccurate menstrual history
• Big baby
• Hydraminos
• Ascites with pregnancy.
• Hydatiform mole
• Uterine myomas
• A closely attached adnexal mass

Antenatal management

• Diet-about 350kcal/day
• Increased rest at home and early cessation of work
• Increased number of antenatal visit
• Supplemental therapy-Fe increase 100-200mg/day, vitamins, calcium and folic acids
• USS- frequent after every 3-4 weeks
• Pre-term labor at a GA of less than 34weeks -give corticosteroids.
• Note: twins develop pulmonary maturity 3-4 weeks earlier than singleton

Management during labor

Vaginal delivery-both or at least one baby in vertex presentation.

• Bed rest-prevent early rupture of membrane
• Fetal monitoring (electronic)
• Internal examination should be done soon after the rupture of the membrane to exclude cord prolapse
• Ringers lactate and 1 unit for BT-ready

Delivery of twin fetuses

Complications of labor and delivery

• Preterm labor
• Uterine contractile dysfunction
• Abnormal presentation, prolapse of the umbilical cord
• Premature separation of the placenta
• Immediate postpartum hemorrhage

Vertex- Vertex (50%)

• Vaginal delivery, interval between twins not to exceed 20 minutes.

Vertex- Breech (20%)

• Vaginal delivery by senior obstetrician

Breech- Vertex (20%)

• Safer to deliver by CS to avoid the rare interlocking twins (1:1000 twins).

Breech-Breech (10%)

• Usually by CS.

Vaginal Delivery

When the first twin is cephalic, delivery can usually be accomplished spontaneously or with forceps.

As in singletons, when the first fetus presents as a breech, major problems are most likely to develop if:

• Fetus is unusually large and the aftercoming head is larger than the capacity of the birth canal.
• Fetus is sufficiently small so that the extremities and trunk are delivered through a cervix inadequately effaced and dilated to allow the head to escape easily.
• Umbilical cord prolapses

Vaginal Delivery of the Second Twin

As soon as the presenting twin has been delivered, the presenting part of the second twin, its size, and its relationship to the birth canal should be quickly and carefully ascertained by combined abdominal, vaginal, and at times intrauterine examination.

If the fetal head or the breech is fixed in the birth:

• Moderate fundal pressure is applied and membranes are ruptured.
• Digital examination of the cervix is repeated to exclude prolapse of the cord.
• Labor is allowed to resume, and the fetal heart rate is monitored.
• With reestablishment of labor there is no need to hasten delivery unless a non-reassuring fetal heart rate or bleeding develops.
• If contractions do not resume within approximately 10 minutes, dilute oxytocin may be used to stimulate contractions.
• If the occiput or the breech presents immediately over the pelvic inlet but is not fixed in the birth canal
• Presenting part can often be guided into the pelvis by one hand in the vagina while a second hand on the uterine fundus exerts moderate pressure caudally.
• Alternatively, an assistant can maneuver the presenting part into the pelvis
• Using ultrasonography for guidance and to monitor heart rate.
• It is essential to have an obstetrician skilled in intrauterine fetal manipulation and an anesthesiologist skilled in providing anesthesia to effectively relax the uterus for vaginal delivery of a non-cephalic second twin to obtain a favorable outcome

Cesarean Delivery

The American College of Obstetricians and Gynecologists (1998) has concluded that, in general, cesarean delivery is the method of choice when the first twin is non-cephalic.

It is important to place patients in a left lateral tilt so as to deflect the uterine weight off the aorta to avoid hypotension.

The uterine incision should be large enough to allow atraumatic delivery of both fetuses.

It is important that the uterus remain well contracted during completion of the cesarean delivery and thereafter.

Remarkable blood loss may be concealed within the uterus and vagina and beneath the drapes during the time taken to close the incisions.

Delivery of the first baby

Babies that are small pose less difficulties

Forceps delivery- if necessary should be under pudendal block anaethesia, avoid general anesthesia as the 2nd baby may be subjected effect of prolong anesthesia.

Don’t give ergometrine

Leave 8-10cm of the cord for administration of any drugs or transfusion

Delivery of the second baby

After delivery of the first baby, the lie, presentation and size of the second baby is ascertained through abdominal examination

Perform vaginal exam to exclude cord prolapse and ascertain membrane status

Delivery the second baby as required

Special case

Twins with previous scar

• Trial of scar if twins has a first vertex should not be an absolute contraindication
• Judicious external or internal manipulations are not contraindicated
• Prefer caesarean if transverse / breech
• Success rate 30-75%
• Risk of uterine rupture is the same as in a singleton pregnancy

During labor

1. PROM
2. Cord prolapse
3. Prolonged labor
4. Increased op interference
5. Bleeding (intrapartum) - IPH
6. PPH

During puerperum

1. Subinvolusion
2. Increased risks of infections
3. Lactation failure

Complications to fetus

1. Still birth/neonatal death
2. Abortion— especially early in pregnancy; vanishing twin/papyraceous
3. Single fetal death in twin pregnancy
4. IUGR (intrauterine growth restriction)
5. SGA (small for gestational age)
6. Higher risks of congenital anomalies
7. Risk of cord accidents
8. Chorionicity
9. Risk of asphyxia
10. Operative vaginal delivery
11. Twin entrapment (during delivery)

Complications of monochorionic twins

• Twin-twin transfussion syndrome (TTTS)
• Dead fetus syndrome, survived twin- cereblal palsy, microcephaly, DIC
• Twin reverse arterial perfusion (TRAP)
• Conjoint twins
• Anterior (thoracopagus)
• Posterior (pygopagus)
• Cephalic (craniopagus)
• Caudal (ischiopagus)

Congenital anomalies

NTD (neural tube defects)

Cardiac anomalies

Bowel Atresia

Conjoint twins

TRAP sequence (twin reversed arterial perfusion)

Acardiac twin

Twin reversed-arterial-perfusion (TRAP) sequence is a rare (1 in 35,000 births) but serious complication of monochorionic, monozygotic multiple gestation.

In the TRAP sequence, there is usually a normally formed donor twin who has features of heart failure as well as a recipient twin who lacks a heart (acardius) and various other structures.

Caused in the embryo by a large artery-to-artery placental shunt, often also accompanied by a vein-to-vein shunt.

The perfusion pressure of the donor twin overpowers that in the recipient twin, who thus receives reverse blood flow from its twin sibling.

Twin to twin transfusion

Blood is transfused from a donor twin to its recipient sibling such that the donor becomes anemic and its growth may be restricted, whereas the recipient becomes polycythemic and may develop circulatory overload manifest as hydrops.

Donor twin - pale.

Recipient sibling – plethoric

Fetal consequences: circulatory overload with heart failure

Occlusive thrombosis is also much more likely to develop in this setting.

Polycythemia may lead to severe hyperbilirubinemia and kernicterus

Pathophysiology

Presence of solitary, deep arteriovenous channels within the capillary beds of the villous tissue.

Velamentous umbilical cord insertion may contribute to the development of unequal fetal blood volumes because the membranously inserted cord can be easily compressed, restricting blood flow to one twin.

Diagnosis

Postnatal diagnosis:

1. Weight discordancy between twins of 15 – 20%
2. Hemoglobin level difference of 5 g/dL or greater

• Typically presents in the midtrimester when the donor fetus becomes oliguric due to decreased renal perfusion Develops oligohydramnios, and the recipient fetus develops severe hydramnios, presumably due to increased urine production.
• Virtual absence of amniotic fluid in the donor sac prevents fetal motion, giving rise to the descriptive term stuck twin.
• Hydramnios–oligohydramnios combination can lead to growth restriction, contractures, and pulmonary hypoplasia in one twin, and premature rupture of the membranes and heart failure in the other.

Management

• Amnioreduction
• Septostomy
• Laser ablation of vascular anastomoses
• Selective feticide

Discordant twins

Size inequality of twin fetuses, which may be a sign of pathological growth restriction in one fetus, is calculated using the larger twin as the index.

As the weight difference within a twin pair increases, perinatal mortality increases proportionately.

Restricted growth of one twin fetus usually develops late in the second and early third trimester and is often asymmetrical.

Earlier discordancy is usually symmetrical and indicates higher risk for fetal demise.

The earlier in pregnancy discordancy develops, the more serious the sequelae.

Pathology

In monochorionic twins, discordancy is usually attributed to placental vascular anastomoses that cause hemodynamic imbalance between the twins.

Dizygotic fetuses may have different genetic growth potential, especially if they are of opposite genders.

Diagnosis

Weight of larger twin minus weight of smaller twin, divided by weight of larger twin.

Most useful index of size discordancy - ultrasonographic assessment of twin discordancy: abdominal circumference superior to head circumference, femur length, or transverse cerebellar diameter

Management

Ultrasonographic monitoring of growth within a twin pair has become a mainstay in the management.

Other ultrasonographic findings, such as oligohydramnios, may be helpful in gauging fetal risk.

Depending on the degree of discordancy and the gestational age, fetal surveillance may be indicated, especially if one or both fetuses exhibit growth restriction.

Delivery is usually not performed for size discordancy alone, except occasionally at advanced gestational ages.

Death of one fetus

Prognosis for the surviving twin depends on the gestational age at the time of the demise, the chorionicity, and the length of time between the demise and delivery of the surviving twin.

Early demise such as a "vanishing twin" does not appear to increase the risk of death in the surviving fetus after the first trimester.

Later in gestation, the death of one of multiple fetuses could theoretically trigger coagulation defects in the mother.

Management decisions should be based on the cause of death and the risk to the surviving fetus.

Majority of cases of a single fetal death in twin pregnancy involve monochorionic placentation.