What is an ultrasound scan?
An ultrasound picture is formed using sound waves, which are passed
through the uterus and reflected back as an image on a screen.
Ultrasound scans in pregnancy may be routine or they may be offered
because of pain or bleeding or because of problems in a previous
pregnancy.
How is it done?
There are two ways of doing an ultrasound scan.
In early pregnancy, especially before 11 weeks, it is usual to have a
trans-vaginal (internal)
scan,
where a probe is placed in the vagina. This gives the clearest and
most accurate picture in early pregnancy. It may also be offered after
11 or 12 weeks if a trans-abdominal scan doesn’t give a clear enough
picture.
From 11 or 12 weeks, including at the routine booking-in scan, it is more common to have a
trans-abdominal scan.
The person doing the scan spreads a special gel on your lower abdomen
(below your belly button and above the line of pubic hair). He or she
then moves the scanner over the gel, sometimes pressing down, until the
uterus (womb) and pregnancy can be seen.
What if I don’t want an internal scan?
If you don’t want a trans-vaginal scan, you can ask for a
trans-abdominal scan. That may give some information about your
pregnancy, but it is less clear than an internal scan and that could
possibly delay diagnosis.
Can scans harm the baby?
There is no evidence that having a vaginal or an abdominal scan will
cause a miscarriage or harm your baby. If you bleed after a vaginal
scan, it will most likely be because there was already blood pooled
higher in the vagina and the probe dislodged it.
When can I have a scan? When can you see the baby’s heartbeat?
An ultrasound scan
may be able to detect a
pregnancy and a heartbeat in a normal pregnancy at around 6 weeks, but
this varies a great deal and isn’t usually advised. All too often, a
scan at 6 weeks shows very little or nothing, even in a perfectly
developing pregnancy, whereas waiting a week or 10 days will make the
findings much clearer.
Routine scans
Most pregnant women are referred for their first
routine ultrasound scan somewhere between 11 and 18 weeks of pregnancy. The purpose of the scan is:
- to confirm that there is a heartbeat
- to assess the baby’s size and growth
- to estimate the delivery date and
- to check whether there is one baby, or twins or more.
Some women may be offered a
nuchal scan between 11 and 14 weeks. The purpose of this scan is to try to detect some chromosome abnormalities, such as Downs syndrome.
Many hospitals also offer a further
anomaly scan at 20 weeks, making a more detailed check of the baby’s development.
You can find out more about nuchal and anomaly scans at the website of the charity
ARC – Antenatal Results and Choices
Sadly…
Sadly, sometimes these scans show that the baby has died, possibly
some weeks earlier and often without any signs or symptoms such as
bleeding or pain. This is often called a “missed” or “delayed”
miscarriage. This can come as a considerable shock and it may take time
before you can take this information in.
You may also have to make some difficult decisions about how to manage the miscarriage process. You can read more about this
here.
Early scans
You may be referred for an early scan because of vaginal bleeding or
spotting, or possibly because you have had problems in a previous
pregnancy.
The best time to have a scan is from about 7 weeks’ gestation
when it should be possible to see the baby’s heartbeat in a normal
pregnancy. But it can be hard to detect a heartbeat in early
pregnancy and in those cases it can be hard to know whether the baby has
died or not developed at all, or whether it is simply smaller than
expected but still developing.
For that reason, you may be asked to return for another scan a week
or so later. At that time, the person doing the scan will be looking
for a clear difference in the size of the pregnancy sac and for a
developing baby and a heartbeat.
Sometimes, it can take several scans before you know for sure what is
happening. It can be very stressful dealing with this uncertainty –
some women describe it as being “in limbo”. You may need to find some
support for yourself if this happens to you.
There’s a heartbeat, but I’m still bleeding…
If the scan does pick up a heartbeat and the baby appears to be the
right size according to your dates, this can be very reassuring, even if
you are still bleeding.
Research
amongst women with a history of recurrent miscarriage has shown that
those who saw a heartbeat at 6 weeks of pregnancy had a 78% chance of
the pregnancy continuing. It also showed that seeing a heartbeat at 8
weeks increased the chance of a continuing pregnancy to 98% and at 10
weeks that went up to 99.4%.
The numbers may be even more positive for women without previous miscarriages.
So things could still go wrong and sadly sometimes do, but as long as
there is a heartbeat, the risk of miscarriage decreases as the weeks go
by.
Other investigations
In some cases, if there is no sign of a pregnancy in the uterus, you
may be given a blood test and possibly asked to return two days later
for a repeat test.
These blood tests measure the level of the pregnancy hormone ßhCG. In
a normally developing pregnancy the hormone levels double about every
48 hours and if the pattern is different, this can help to identify what
is happening to the pregnancy.
If there is no sign of a pregnancy in the uterus and you have
symptoms that suggest ectopic pregnancy, you are more likely to have
both a blood test and an investigation called a laparoscopy, which is
done under general anaesthetic. You can read more about this in our
leaflet
Ectopic pregnancy.
Scan results – and what they mean
The ultrasound scan may show:
- A viable ongoing pregnancy. There is a heartbeat (or heartbeats if
it’s a twin or multiple pregnancy) and the pregnancy is the “right size
for dates” – that is, the size that would be expected based on the first
day of your last period. Those are positive signs, but if you continue
to bleed, you may need a further scan in a week or two to check what’s
happening.
- An ongoing pregnancy that suggests a problem. Perhaps the pregnancy
is much smaller than it should be according to dates or the heartbeat
is particularly slow or faint. Perhaps there is something that suggests
a problem with the baby’s development. With a twin or multiple
pregnancy, the scan may show that one (or more) baby has a heartbeat and
one (or more) doesn’t. You may be asked to come back for another scan,
possibly in a week or two when things should be clearer.
- A pregnancy of unknown location (PUL). The pregnancy is too small
for the heartbeat to be visible, or there may be nothing much to see at
all and it’s not clear what is happening. You will probably be asked to
come back for another scan, possibly in a week or two when things
should be clearer. Or if the doctor thinks you might have an ectopic
pregnancy, you will have blood tests and/or a laparoscopy.
- A complete miscarriage. The pregnancy has miscarried. There may still be a small amount of tissue or blood in the uterus.
- A non-viable pregnancy. This means a pregnancy that hasn’t survived
but hasn’t yet miscarried. You may hear this described in one of the
following ways:
- Missed miscarriage (also called silent or delayed miscarriage or
early embryonic demise) This is where the baby has died or failed to
develop but your body has not miscarried him or her. The scan picture
shows a pregnancy sac with a baby (or fetus or embryo) inside, but there
is no heartbeat and the pregnancy looks smaller than it should be at
this stage. You may have had little or no sign that anything was wrong
and you may still feel pregnant.
- Blighted ovum or anembryonic pregnancy (which means a pregnancy
without an embryo). This is a rather old-fashioned way of describing a
missed miscarriage (see above). The scan picture usually shows an empty
pregnancy sac.
- Incomplete miscarriage The process of miscarriage has started but
there is still pregnancy tissue in the uterus (womb) and you may still
have pain and heavy bleeding.
In all of these situations, the pregnancy will fully miscarry with
time, but there are several ways of managing the process. You may be
offered a choice, or the hospital might make a recommendation. In most
cases, you should be able to have time to think about what you can best
cope with. You can read more
here.
The ultrasound scan might show
- An ectopic pregnancy. This means a pregnancy that is developing
outside the uterus (Ectopic means “out of place”). Ectopic pregnancies
usually develop in one of the Fallopian tubes, but they can develop
elsewhere inside the abdomen. You can read more in our leaflet Ectopic pregnancy.
- A molar pregnancy. This is a pregnancy where the baby can’t develop
but the cells of the placenta grow very quickly. It can’t always be
diagnosed on scan so you might find out only after the miscarriage. You
can read more in our leaflet Hydatidiform Mole.
