Early Pregnancy Scans and Problems
Why would an early pregnancy scan be done?
Most pregnancies are normal, but some have problems. The most common problem is miscarriage, or the much rarer problem of an ectopic pregnancy. If a woman has bleeding in early pregnancy, or abdominal pains it is helpful to have a scan.
When in pregnancy?
Very early in pregnancy there may not be very much
to see on scan, so we try to time the scan to be at least
6 weeks from the last period, 4 weeks from conception or
2 weeks from the first positive pregnancy test. Sometimes
problems can be seen before this stage, but it is not usually
possible to see a normal pregnancy, so reassuring someone
that everything is OK is very difficult.
How do you know a pregnancy has miscarried?
Most women will have vaginal bleeding, which prompts a scan, but sometimes the pregnancy will fail without giving any symptoms (this is called a missed miscarriage). The scan will show a pregnancy which is failing to develop normally. The key feature on an early pregnancy scan is to see the fetal heartbeat. If the fetal heart is beating, then the circulation has been established and the pregnancy will continue to develop. A fetal heart can normally be seen from 6 weeks of pregnancy, 4 weeks from conception or 2 weeks after the first positive pregnancy test. The pregnancy first appears as an empty sac, then a small ring called a yolk sac is seen and finally the fetus with a beating fetal heart. If there is no pregnancy development to see within the uterus from 6 weeks gestation the most likely reason is miscarriage, but we also need to consider ectopic pregnancy.
What is an ectopic pregnancy?
An ectopic pregnancy is where the pregnancy develops outside the uterus, usually in the fallopian tube. It is a potentially dangerous condition because it causes internal bleeding.
Ectopic pregnancy usually presents as vaginal bleeding and abdominal pain, but these symptoms are very variable. Anyone who has a positive pregnancy test, is more than 6 weeks from their last period and has no pregnancy seen on ultrasound scan within the uterus may have an ectopic pregnancy. Sometimes the pregnancy can actually be seen outside the uterus (about 10% of cases), but often the pregnancy is not easy to see directly and we would rely on other signs (indications of bleeding inside the pelvis). If the situation is unclear it may be helpful to do a pregnancy blood test which tells how much pregnancy hormone is being produced. This test is called a quantitative HCG and can be undertaken at the same time as the ultrasound assessment, although the results will not usually be available later the same day, or the following day.
If an ectopic pregnancy is suspected or seen for certain the usual treatment would be to remove the pregnancy by keyhole surgery.
What does the scan involve?
The scan is in 2 parts.
The first part is an abdominal scan that scans through the abdominal wall. If the images are clear and the fetal heart can be seen then there is no need to do the second part of the scan which is a vaginal, or internal scan.
If the pregnancy cannot be clearly seen with the abdominal scan then the internal scan is very helpful. This scan involves putting a specially designed scan probe into the vagina which is then much closer to the uterus, fallopian tubes and ovaries than the abdominal scan. Depending on where everything is inside the body it may be necessary to lift your bottom off the scan couch by putting a cushion underneath you. The scan doesn’t hurt, and it cannot cause a miscarriage or any other problems.It should only take a couple of minutes to get good images, and to get whatever information we can.
What do we see on scan?
A pregnancy sac looks like a black circle in the middle of the uterus. A yolk sac looks like a white circle within the black circle. The fetal pole is light grey and the fetal heart can be seen moving within the fetal pole. To help to show the fetal heart beat we sometimes use the listening device within the scanner, and sometimes we use colour, but these are only used to a short time to be able to demonstrate the heartbeat clearly.
How is a pregnancy dated?
A pregnancy is dated from the first day of the last period. In a textbook pregnancy the conception will happen on day 14, so you are already 2 weeks pregnant when you conceive!
The first missed period is on day 28 (4 weeks) and most people will do a pregnancy test around 5 to 6 weeks. Some people have terrible pregnancy symptoms of tiredness and sickness, but many have no symptoms at all.
The first signs of a pregnancy on scan are at about 5½ weeks with a pregnancy sac seen, but it is not until 6 weeks that the fetal pole and fetal heart are present. The traditional approach has been to date from the last period, but we can be more accurate with ultrasound scanning.
The ideal time to date a pregnancy is between 8 and 12 weeks by measuring the length of the baby (crown-rump length or CRL) alternatively the fetal head can be measured from 12 weeks onwards (either the distance across the head (BiParietal Diameter - BPD), or around the Head (Head Circumference - HC). There are some exceptions to the principle of dating by scan measurements, mostly surrounding other important information such as IVF or other certain dates.
Is a pregnancy test important?
Yes very important.
Modern pregnancy tests are very sensitive, and if the pregnancy test is negative then the pregnancy hormone levels are very low indeed. If a pregnancy test is negative we would not expect to see any pregnancy related problems on scan. Other things can still cause abnormal bleeding and pain, sometimes requiring ultrasound assessment, but this would not be an early pregnancy scan.
Can you recommend management?
When the scan has been done there are a number of possible outcomes.
The pregnancy could be obviously OK with the fetal heartbeat clearly seen. No further scanning would be needed, and the vast majority of pregnancies (at least 90%) will go on to be successful. We would give you your report and pictures and calculate a due date. It may not be clear from one scan what is happening. You may be advised to attend for a follow-up scan a week or two later to ensure the situation was clear before we can tell you what is happening.
It may be clear that the pregnancy has miscarried.
The findings of the scan and the interpretation would be discussed with you. Miscarriage management can take several different styles, each of which has advantages and disadvantages, these will be discussed with you.
We may be suspicious of an ectopic pregnancy, which would be discussed. If you are eligible for NHS treatment locally then we can refer you into the hospital systems, or you can go back through your own GP or midwife.
We have facilities to offer private treatment at BMI Thornbury Hospital. Private treatment is often covered by your medical insurance company, although some policies exclude pregnancy complications.
It may be worth contacting your insurer before you come for the scan as some policies insist that you get prior approval before being seen, we will complete any insurance forms or send additional reports to your insurer free of charge.