| | NOTE: The following information is provided for your information
only and does not necessarily reflect each person's individual situation. If you
have any concerns whatsoever about your pregnancy, please consult your physician
immediately.
Twin to twin transfusion syndrome (TTTS) is a random abnormality of a
monochorionic placenta that causes one identical twin to receive less than
normal amounts of blood supply during pregnancy while the other receives too
much. The babies share blood vessels in their placenta that cause an imbalance
of blood flow and nutrients between them. There are degrees to the severity of
the syndrome, but it is always life-threatening due to the fact that it can
worsen at anytime during pregnancy. Below is a summary of the difference between
dizygotic (fraternal) and monozygotic (identical) twin pregnancies. TTTS can
only happen with monozygotic twins, or as a pair in a higher multiple pregnancy,
that share a single monochorionic placenta.
There are two types of twins:
DIZYGOTIC (DZ) - two eggs meet up with two sperm. These babies
are technically siblings who happen to have been born at the same time. They are
commonly known as "fraternal". They always have one placenta each and
are called dichorionic (DC).
MONOZYGOTIC (MZ) - one egg meets up with one sperm. These
babies are always the same gender and are commonly known as
"identical". MZ pregnancies can experience high complication rates,
particularly if the twinning process occurs more than 4 days from fertilization
resulting in a single monochorionic placenta share by two or more babies.
There are two types of monochorionic pregnancies that can be affected by twin to
twin transfusion syndrome:
MONOCHORIONIC-DIAMNIONIC
When the embryo randomly splits between 4-8 days after conception, the pregnancy
results with two babies each in their own amniotic sac (diamnionic) as well as
sharing a placenta (monochorionic). The majority of these pregnancies proceed
without complications. However, approximately 15% of the time, the babies will
share blood between them disproportionately and warning signs of the syndrome
will appear on ultrasound (see warning signs below). The syndrome can occur with
two or more babies in a higher multiple birth pregnancy as long as the babies
share a single monochorionic placenta.
MONOCHORIONIC-MONOAMNIOTIC
When the embryo randomly splits between 8-12 days after conception, the
pregnancy results with both babies sharing a single placenta (monochorionic) but
the babies are in the same amniotic sac (monoamniotic). This type of pregnancy
can still result in TTTS but it is more difficult to diagnose with the babies in
the same sac. Also, there is a greater concern that the babies' cords will
become entangled. It is estimated that approximately 50% of the babies will pass
away from cord entanglement. It is recommended that mothers be hospitalized at
24 weeks for 24 hour monitoring of the babies until they are born.
One of the warning signs of TTTS shown on ultrasound is a size difference in the
babies. One baby, the donor, becomes restricted in growth receiving less then
normal blood flow. The donor baby does not urinate very much and has little to
no fluid in his or her amniotic sac. Sometimes the baby is referred to as a
'stuck twin' or having oligohydramnios. Subsequently, a much larger blood flow
goes to the co-multiple, referred to as the recipient twin. Due to the shared,
interconnecting veins and arteries in the single placenta, the blood
disproportionately flows through the donor twin and collects in the recipient
twin, who is unable to efficiently rid his or herself of the extra blood. The
recipient baby urinates frequently causing too much amniotic fluid or
polyhydramnios. Because of this abnormality in the placenta, both babies'
well-being can be severely compromised.
MATERNAL MIRROR SYNDROME
In cases with extreme fetal hydrops, the mother may be at risk for maternal
mirror syndrome, which is a condition where the mother's condition mimics that
of the sick fetus. Because of a hyperdynamic cardiovascular state, the mother
develops symptoms that are similar to pre-eclampsia and may include vomiting,
hypertension, peripheral edema, proteinuria and pulmonary edema. Despite
resection of the anomaly, maternal mirror syndrome may still occur.
PLACENTAL SHARE
It is important to understand that one reason babies can become growth
restricted is that the babies may share the placenta itself unequally. The donor
baby could have less then half of the placenta to nourish it. This is one reason
why The Twin to Twin Transfusion Syndrome Foundation advocates weekly
ultrasounds from 16 weeks through delivery of the babies. If a baby has a small
placental share, and you cannot know prior to birth for sure what the placental
share is, the baby will get to a certain gestational week and it will stop
growing. The baby will not get enough blood and oxygen from it s share of the
placenta to 'get bigger' than the size that it is. The rate of growth for the
babies is extremely important and is often overlooked. The sharing of the blood
from the syndrome also adds to size differences of the babies. TTTS is often
combined with an unequal placental sharing.
Some treatment options are available:
AGGRESSIVE SERIAL AMNIOCENTECES removal of the excess fluid around the recipient
which may need to occur several times;
LASER SURGERY which identifies the connecting blood vessels in the shared
monochorionic placenta and cauterizes them with a laser beam. The babies are
being separated in the placenta so each will then get their blood supply
independently from the other. The scope used is inserted through amniotic cavity
of the recipient baby. There are specific criteria that must be met based on
ultrasound findings.
BEDREST AND NUTRITION which is explained below and combined with the therapies
listed above.
What Can We, as Parents, Do?
- Make sure your obstetrician has plenty of high-risk pregnancy experience.
- Make sure that your obstetrician uses intensive ultrasound to determine
the chorionicity (DC or MC) of the babies as early as possible in the
pregnancy. If the babies are like-sexed, you need to know if they share a
placenta or each have their own. If they share a placenta, weekly
ultrasounds are crucial in the care of your babies and you may have to
really fight to have them. Don't take no for an answer. If the babies are
unlike-gender, they must be fraternal twins and cannot have TTTS. Keep
asking questions until you are satisfied and understand the answers.
- If your babies are monochorionic, take really good care of yourself.
Nutrition is completely overlooked by most doctors. Bedrest is also strongly
encouraged along with adding liquid protein. Bedrest is defined as laying
horizontally on your left side and getting up to eat, shower, use the
bathroom, and go to appointments. Laying on your left side takes pressure
off of your cervix and helps increase blood and oxygen to the placenta to
help your babies.
- Make sure that your cervix is checked weekly. This is also overlooked by
many doctors. If your cervix length shortens to 2cm or less, a cerclage or
stitching of the cervix can be done up through 25 weeks.
- If early signs of TTTS appear, or there is a sudden increase in your size,
ask for a perinatology appointment immediately. Your fetal-maternal medicine
specialist will know about the options for treatment. Ask what they think
about possible laser treatment and whether this is a possibility for you.
Once again, don't take no for an answer.
- Understand a monochorionic placenta and what TTTS is. Understand
specifically what is happening to your babies with measurements of their
size difference, your fundal height, the biggest pocket of fluid around each
baby, where your placenta is located in the uterus, their doppler readings
and your cervix. Create a medical plan of action with back-up plans so
you can be as prepared as you can for each appointment.
Warning Signs of TTTS
- a large-for-dates uterus
- water in baby(ies) body (heart failure called hydrops)
- a single placenta
- same sex babies
- growth discordance, babies are growing at different rates
- too much amniotic fluid in one sac and too little in the other
- being 16-26 weeks pregnant with fundal height of 30 cm or more
- a doppler reading for the babies which is absent diastolic or reverse flow
- a cervix which is thinning and shortening to 2cm or less
- sudden weight gain and/or swelling in the mother's body
The later the condition develops in the pregnancy, the better chance the babies
have since they could be delivered if signs of distress are present. Your health
care professional is the best source of information regarding your personal
situation and can discuss fully with you how your situation can be managed. However,
remember that the ultimate decisions for your children are yours.
Definitions:
Diamniotic twins: twins who have developed in separate amniotic sacs. They may
be either dizygotic or monozygotic.
Dichorionic twins: twins who have developed in separate chorionic sacs. They may
be either dizygotic or monozygotic.
Dizygotic twins: twins formed from two separate zygotes.
Fraternal twins: see dizygotic twins
Higher order multiples: triplets, quadruplets, quintuplets or more
Hydropic (hydrops): a condition due to the abnormal accumulation of serous fluid
in the tissues or in a body cavity
Identical twins: see monozygotic twins
Monoamniotic twins: twins who have developed in a single amniotic sac. These
twins are always monozygotic.
Monochorionic twins: twins who have developed in a single chorionic sac. These
twins are always monozygotic.
Monozygotic (monozygous) twins: twins formed from a single zygote.
Oligohydramnios: the presence of too little amniotic fluid around a baby.
Polyhydramnios: the presence of too much amniotic fluid around a baby.
Serous fluid: a thin and watery fluid
Twin to twin transfusion syndrome (TTTS): results from abnormalities of the
placenta in monozygous twin pregnancies. TTTS results from blood passing
disproportionately (transfusing) from one twin baby to the other through
connecting blood vessels within the shared (monochorionic) placenta. (TTTS
Foundation)
Zygote: a fertilized ovum.
Information take from:
Lynda P. Haddon, Multiple Birth Educator
UCSF
Other Resources:
|
