637 4060 ADDRESS: 60 Mount Street Lower, Grand Canal Dock, Dublin 2 info@merrionultrasound.ie

Miscarriage Diagnosis Guidelines

Miscarriage Diagnosis Guidelines FAQs

How can I be assured that my miscarriage diagnosis on scan was accurate?

Merrion Fetal Health follows the guidelines of The National Maternity Hospital and the Royal College of Obstetricians & Gynaecologists to ensure that misdiagnosis does not occur. These guidelines err on the side of caution and outline strict criteria for making the diagnosis of miscarriage.

What are these criteria to make a diagnosis of miscarriage?

The guidelines run to 18 pages and make many recommendations but broadly speaking an ultrasound should be carried out by appropriately trained personnel with appropriate ultrasound equipment (including transvaginal probes). In many cases, a fetus/embryo with a regular heartbeat will be identified in a healthy pregnancy sac within the womb. The ultrasound allows measurement of the size of the fetus and the sac to determine how far the pregnancy is. Sadly, it is often the case that we identify an embryo/fetus in a pregnancy sac but cannot see a heartbeat and this may mean the pregnancy is too early or not viable.

Because of the difficulties in seeing a heartbeat in very early pregnancies, there are strict criteria which we follow to ensure that we do not diagnose a miscarriage in what could be a healthy but very early pregnancy where it is not possible to see the heartbeat yet. Thus, if the pregnancy sac is less than 20mm in size or if the size of the embryo/fetus is less than 6mm and a heartbeat cannot be seen, a definitive diagnosis cannot be made and the scan should be repeated in 7 to 10 days time.

Why is it necessary to sometimes perform an internal (transvaginal) scan?

An internal scan allows better visualisation of the womb and its contents. This is because the soundwaves do not have to travel far because the tip of the probe is inserted very close to the womb and gives a much better picture than an abdominal (transabdominal) scan. With this approach, the soundwaves have to travel through your tummy wall and occasionally the images obtained are not clear enough to make a definitive diagnosis. Thus, in very early pregnancy, in overweight women or when the womb is tilted backwards, or when a clear diagnosis cannot be reached with a transabdominal scan, a transvaginal approach might be necessary.

I have been told I have a miscarriage, but I still feel pregnant. What does this mean?

This is a very common scenario because the hormones that are released by an early pregnancy that is failing can still cause pregnancy symptoms.

I have been told I have a miscarriage, but my pregnancy test is still positive. What does this mean?

Again, the hormones that are released in early pregnancy can give a positive pregnancy test. These hormones can stay in the blood for some time after the pregnancy has failed and will give a positive pregnancy test as these hormones are released into the urine which then gives a positive pregnancy test. This can occur for up to 3 weeks following any type of miscarriage.

Why was I not offered a second scan?

It is very often unnecessary to do this as the first scan diagnosis can be definite if the above criteria can be met. If there are any doubts about diagnosis a second scan will be performed, sometimes on the same day, but more often 7 – 10 days later. Some women miscarry completely and the womb or uterus will appear empty when scanned. In this case, no follow up procedure will be necessary.

What are the limitations of ultrasound?

Occasionally, ultrasound in early pregnancy may be inconclusive if the gestation is too early, particularly if you are less than 7 weeks or if you are unsure of your dates. This is because the pregnancy may be too small to be seen before 7 weeks. In order to be absolutely accurate in the diagnosis of early pregnancy before 7-8 weeks, it is recommended by all best practice guidelines, to repeat the scan after an interval of at least a week, if there is uncertainty or doubt.

What is the earliest you can diagnose a miscarriage?

All bleeding that occurs in the early weeks of pregnancy is referred to as a threatened miscarriage. Viability is uncertain in about 10% of pregnancies. Under 7 weeks a diagnosis can be difficult. When a miscarriage is suspected, an ultrasound scan is carried out to establish what the likely outcome will be. If it is confirmed that the pregnancy is not continuing, the scan findings will suggest whether there is a need for further treatment. Some women miscarry completely and the womb or uterus will appear empty when scanned. In this case, no follow up procedure will be necessary.

What happens if a miscarriage is diagnosed?

There are various treatment options which would include awaiting for a spontaneous miscarriage which usually involves heavy bleeding, similar to a heavy period. This approach might be recommended if there is a small amount of tissue in the womb. An alternative treatment would be to use a medication called Cytotec which might induce a miscarriage and is also used prior to ERPC/D&C. If there is a big pregnancy sac and/or a lot of tissue in the womb the usual recommendation will be to undergo an ERPC/D&C.

What is an ERPC? (also called a D&C)

ERPC stands for Evacuation of Retained Products of Conception and is a procedure performed under general anaesthetic that involves removing the remaining blood clots and pregnancy sac from the womb in order to stop further bleeding. Although instruments are passed into the womb no actual surgery takes place and no stitches are needed.

What happens if I decline an ERPC/D&C?

If you decline to have an ERPC (D&C) this will be your decision. The benefits and risks of the above treatment options will be discussed with you so that your decision is informed. Occasionally miscarriage can be accompanied by very heavy bleeding, necessitating blood transfusion and may pose risks to your overall health and well being. The other reason for suggesting an ERPC is if pregnancy tissue remains in the uterus (womb) this can lead to infection which occasionally can be serious.

What is an ectopic pregnancy – does this not mean I am still pregnant?

This is when the pregnancy implants and grows outside the womb, usually in the fallopian tubes or occasionally the ovary. The symptoms usually include acute pain and slight bleeding. A scan is normally performed to assess whether this suspected diagnosis is correct. An ectopic pregnancy is a serious complication and it is not possible to save the pregnancy. Surgery is usually required but sometimes medication can resolve this. More information here by clicking on ectopic pregnancy.

Are all scanning staff appropriately qualified in Merrion Ultrasound?

The sonographers and obstetricians in Merrion Ultrasound are all highly qualified in scanning and are very experienced. You can meet some of our sonographer team here.

Professor Fionnuala Mc Auliffe Miscarriage Diagnosis Guidelines Video

Transcript – Professor Fionnuala Mc Auliffe Miscarriage Diagnosis Guidelines Video

Video title: Miscarriage Diagnosis By Ultrasound Scans

Sometimes miscarriages occur in pregnancy and ultrasound is really important in making the diagnosis. The diagnosis of miscarriage can be difficult before seven weeks because the little heartbeat doesn’t come in until about six and a half or seven weeks of pregnancy, so often we may have to repeat the scan to be absolutely sure that in fact, the pregnancy has miscarried, as we want to avoid any possibility of over-diagnosing miscarriage.

Certain strict criteria are adhered to and these may be present at one scan but it would not be unusual that people might have to come back for two or three scans, to diagnose miscarriage.

Once miscarriage is diagnosed, there are three options. One is to wait for the body to naturally miscarry. This can take anything from a few days to a few weeks. The second option is to take medication, which can speed up the natural process. The third option is to have a surgical operation where the patient comes into the hospital is put to sleep and the womb is cleaned out. Those three options will be discussed with you following the diagnosis of miscarriage.


Further suggested reading: Miscarriage medical reasons why it happens and how to cope


Nuchal Translucency

12-14 weeks


Anatomy Survey

21-22 weeks


Later Dating

10-17 weeks


Gender Scan

19 weeks onwards


Growth & Well Being

22 weeks onwards


Post Dates & Liquor

40 weeks onwards


What Our Patients Say

Gráinne Macken

This is my second visit to Merrion Fetal, I was very pleased on both occasions. Lovely quiet waiting room, appointment was on time. The 20-week scan is very detailed we enjoyed watching our baby on the large TV screen. We got some beautiful photos. The nurse was very pleasant and talked us through all the measurements and anatomy. I would highly recommend this scanning clinic.”

Áine Gibney

I had the best experience at the Merrion Fetal Health clinic for my 20-week big scan. The staff were so friendly and so nice and the lovely lady who did my ultrasound scan was amazing. She was so thoroughgoing to absolutely everything and gave me such reassurance on how my baby was growing and developing. I would recommend any Mother to be to attend here if you are looking for a comfortable, reassuring and super pleasant experience.”

Linda O'Sullivan

Highly recommend! We had an early scan due to a little scare at the start of pregnancy and then another at 12 weeks to make sure all was good again. Helen who was scanning on both days was fantastic. We felt totally relaxed and un-rushed while she took her time finding the best angle of baby to get us the clearest pictures as keepsakes all while making sure everything was perfect with baby. She reassured us throughout and I can honestly say it was the best money we ever spent getting both scans done.

Please let Helen know we are 18 weeks now and flying along Highly recommend!



About The Clinic

Merrion Fetal Health Pregnancy Scans Dublin 2

About The Consultants

Dr. Rhona Mahony

About The Team

Pregnancy scans lead sonographer at Merrion Fetal Health

Book Your Scan

Screen of Pregnancy Scan

Common Concerns

FAQs - Your Questions


GP Referral Scheme


Health Conditions


Healthy Pregnancy


Medical Studies


Patients' Information


Pregnancy Diary


Pregnancy Magazines

pregnancy health magazines

Scans & Services

18 weeks pregnancy scan facial profile Merrion Fetal Health

Susan's Trimesters

pregnancy trimesters

Videos By Consultants


Midwife sonographer facilitated

Consultant Led, Centre of Medical Excellence 


All articles on the blog and website are intended as information only. Please do not consider any of the information provided here as a substitute for medical advice. At all times seek medical advice directly with your own doctor and medical team.


This website was formerly Merrion Fetal Health. The clinic has undergone a rebrand and is now known as Merrion Ultrasound.