| What
types of scan are available?
Early
viability scan (6 – 10 weeks)
This scan can confirm the number of babies in the uterus
(womb) and can detect a heartbeat by 6 weeks. In early
pregnancy, it may be necessary to perform an internal scan
(trans-vaginal scan) to obtain clearer images of your baby
and its surroundings. A clear explanation of the procedure
and what has been found during the scan will be given to
you during the examination. Scans at this stage in pregnancy
are reassuring for women experiencing bleeding, pain or who
have had previous miscarriages.
Nuchal
translucency scan (11– 13+6 weeks) for Down's
syndrome and other chromosomal abnormalities with
a blood test
Most of the babies we scan with ultrasound at the clinic
are normal and go on to develop normally in the womb. However
all women, whatever their age, will have a small risk of having
a baby with a problem.
One
of these problems can be due to a chromosomal abnormality
such as Down’s syndrome.
The most accurate way of estimating the risk of a baby having
a chromosomal abnormality without having an invasive test
such as an amniocentesis or chorionic villus sampling (see
below) is to undertake a nuchal translucency scan with a
blood test. This combined test has an accuracy of about 92%
whilst the nuchal scan on its own has an accuracy of about
70%.
The
nuchal translucency is an area of fluid behind the baby’s
neck. An increase in the amount of fluid may indicate an
increased risk of a chromosomal abnormality, such as Down’s
syndrome.
We
can now combine the mother’s age,
the size of the baby, the nuchal thickness measurement,
the presence or absence of a nasal bone with a blood sample
taken from the mother to give a more accurate risk assessment
of a chromosomal abnormality as early as 12 weeks.
We usually take the blood sample from 10 weeks onwards and
send it away to a laboratory specialising in this type of
screening. When we take your blood we will carry out an ultrasound
scan to:
- Confirm your dates - this is particularly relevant if
you cannot recall the date of your last period or have
an irregular cycle. We will be able to tell you when your
baby is due
- Show
you the baby’s heartbeat -
this is particularly reassuring at this stage in pregnancy
when you cannot feel your baby move or if you have had
a miscarriage in the past
- Detect multiple pregnancies - approximately 2% of natural
conceptions and 10% of assisted conceptions result in multiple
pregnancies. We can show you that your babies are developing
normally and see if they are identical or not
- Diagnose
an early pregnancy failure – sadly
about 3% of women who come for a nuchal scan may find
that the baby has died, often several weeks before and
without any warning
We
then ask you to come back after 12 weeks so we can measure
the nuchal thickness and check your baby’s
anatomy as some problems or abnormalities may be visible
at this gestation but this still means that you should
attend for your 20 week scan (you can choose to do this
at KMI or in your local NHS hospital) as not all problems
can be detected at this stage.
If you cannot come in two visits it generally is not a problem
- we will discuss the different options we can offer you.
A computer program will be used to estimate the risk by
combining all the factors. Most of the examinations are low
risk. However, if you are one of the unfortunate few with
a high risk, the results will be discussed with you and the
follow up counselling will be arranged. This does not have
to be on a private basis.
We have been fully trained by the Fetal Medicine Foundation
and are regularly audited by them to ensure we continue to
perform at the highest standard. [www.fetalmedicine.com].
As we have mentioned the only way to know for sure whether
or not the baby has a chromosomal abnormality is by having
an invasive test such as chorion villus sampling (CVS) or
amniocentesis. We can arrange for you to have these done
privately through the Fetal Medicine Centre or refer you
to a consultant in the NHS
- Chorionic villus sampling (CVS) is offered up to 15 weeks
of pregnancy. A very fine needle is inserted through the
maternal abdominal wall, usually under ultrasound control,
into the placenta and a tiny piece of placenta is removed.
This is sent to a specialised laboratory where it is used
to examine the developing fetal chromosomes. Results are
usually available within a week
- Amniocentesis is another test offered from 15 weeks of
pregnancy. A very fine needle is passed through the mother's
abdominal wall into the fluid which surrounds the baby
(amniotic fluid). This is usually carried out under ultrasound
control. A small amount of fluid is aspirated and sent
to the laboratory to examine the fetal chromosomes. The
results are usually available within two weeks
Both these tests can carry a risk of miscarriage of about
1% but this risk is dependant on the clinician carrying out
the test.
Fetal
anomaly scan (20 – 23 weeks)
After
checking your baby’s heartbeat, the
main purpose of this scan is to check your baby’s anatomy
for normality. A thorough examination of your baby’s
brain, heart, spine, kidneys, organs and limbs will be undertaken.
The placenta will be checked for its position and measurements
of your baby will be performed to ensure it is growing normally.
Anomaly scans are important as they can reassure the parents
that everything appears to be as it should be; however, in
a few cases a potential problem may be indicated. In these
cases a further follow up scan may be needed and it may be
necessary for us to discuss the problem with your midwife
or doctor. We will explain any complications of the pregnancy
with you at the time of scan and give you advice and guidance
where we can.
We are happy to look for the sex of your baby during this
scan, however, ultrasound is not 100% accurate and this is
only an opinion and not a guarantee of one particular gender.
Growth
and fetal well-being scan (24 weeks - to term)
Measurements
of your baby’s head, abdomen and femur
(thigh) are taken and plotted on graphs to check that your
baby is growing normally. From these measurements we are
able to estimate your baby’s weight. The amniotic fluid
(water surrounding the baby) is assessed along with the position
of the placenta to ensure that it is not near the birth canal
which could affect delivery. This scan can also confirm the
position of your baby.
3D/4D bonding and fetal well being scan
Ultrasound
is the only non-invasive way to see a baby in the womb. Recent
advances in imaging have resulted in the introduction of three-dimensional
(3D) and four-dimensional (4D) ultrasound.
Used
in conjunction with traditional two-dimensional (2D) ultrasound,
3D/4D ultrasound provides more detail in “real” time,
so your baby can be seen moving around.
A
3D/4D ultrasound scan can be undertaken at any stage in
pregnancy but the best time is between 26 – 32 weeks
for the most realistic pictures. At this stage we will clearly
be able to see your baby’s face, hands, fingers, feet
and toes as well as any facial movements or gestures it may
be making.
Many parents-to-be have commented on the amazing quality
of the pictures, even noting genetic similarities to family
members. In this respect, the 4D scan has been shown to promote
maternal and paternal bonding.
There can be limitations sometimes with a 3D/4D scan. If
there is inadequate amniotic fluid surrounding your baby,
or if it has its face covered or is looking away, making
it difficult to get a clear picture of the face.
If
we can’t get good pictures for you then we will
rebook you or only charge you for a growth and well-being
scan, which we would normally do anyway.
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