One in four women will experience a miscarriage, often before they’re even aware of being pregnant.
Being told a pregnancy isn’t viable can be the most devastating news parents-to-be will ever hear.
In many cases, the pregnancy ends naturally. In some situations, a woman might wish to have a procedure to empty her uterus.
The process of deciding what to do can be overwhelming.
Is Miscarriage Ever Misdiagnosed?
The most important thing for women is to be absolutely sure they’re having a miscarriage before making a choice about treatment.
Rarely, pregnancy loss is misdiagnosed and the embryo is discovered to be growing and healthy.
This can be a huge shock to couples who have been mourning the loss of their baby, and trying to make big decisions about treatment.
How Are Miscarriages Diagnosed?
When miscarriage is suspected, care providers follow certain guidelines in making a diagnosis.
A woman experiencing signs of miscarriage will naturally seek medical advice from her maternity care provider.
A miscarriage is diagnosed using a combination of tests, including a blood test to measure hCG (pregnancy hormone), an ultrasound and possibly a pelvic exam.
The blood test is commonly used in very early pregnancy, as the hCG levels usually double every 2-3 days. If the levels aren’t increasing as expected, this can indicate a problem.
If the levels are dropping, a miscarriage is likely. Two tests will be taken, at least two days apart, to give the best results.
Ultrasound is more useful than hCG blood tests at around the six week mark, when the embryo’s heartbeat can be seen. Until week eight, a transvaginal ultrasound is more accurate. Ultrasound might detect visible problems, lack of development of the gestational sac, or no heartbeat.
Pelvic examination might be suggested if your care provider thinks your cervix is dilating. A dilated cervix indicates a miscarriage is likely. Spotting and light vaginal bleeding are common during early pregnancy, and if the cervix isn’t dilated, this is considered a threatened miscarriage.
How Can Miscarriage Be Misdiagnosed?
Although it is rare, miscarriage can be misdiagnosed. And it can have a potentially devastating outcome.
Recently, a New Zealand woman was moments away from terminating a miscarried pregnancy when a final ultrasound showed her baby was alive and well.
Where there is a misdiagnosis of miscarriage, in most cases it occurs in these specific situations.
Date Confusion
Embryos grow very fast in early pregnancy, and their measurements are taken via ultrasound to determine gestational age. This early ultrasound, often called a dating scan, also aims to detect a heartbeat.
Women who have irregular cycles or are unsure about the date of their last menstrual period might be told their normal pregnancy is not viable if the ultrasound doesn’t show the expected development, counting from the last menstrual period.
In some cases, conception actually occurs later than expected, especially as sperm can remain active for up to a week in the right conditions.
Implantation of the fertilised egg can take even longer.
All these factors can lead to indications the embryo is slow to develop and likely to miscarry. In fact the embryo might simply be behind the expected schedule.
For these reasons, the current method of dating a pregnancy, based on the last menstrual period, isn’t failsafe.
Misdiagnosis of miscarriage can occur if a follow up ultrasound isn’t performed. A further scan will check for continued development of the embryo and gestational sac.
The usual waiting time between scans is one week, as a non-viable pregnancy will show no or very minimal growth.
A viable pregnancy will show definite development after this time. If the woman is believed to be up to eight weeks pregnant, a transvaginal scan should be performed to give a better picture of the uterus and embryo.
hCG Levels
Slow rising hCG levels are generally considered to be a sign of a possible ectopic pregnancy. However, it is not uncommon for viable pregnancies to experience similar slow rising levels of hCG.
Falling hCG levels will almost always mean the pregnancy is no longer viable, but very rarely they can indicate a heterotopic pregnancy. This occurs when there are two conceptions – involving a viable pregnancy in the uterus, and another non-viable ectopic pregnancy.
Heterotopic pregnancy is more common with assisted fertility treatments; the occurrence is as high as 1 in 100 pregnancies. In natural conception, it occurs in less than 1 in 30,000 pregnancies.
Falling hCG levels in a viable pregnancy can also occur in ‘vanishing twin syndrome’. This is a twin pregnancy, in which one baby is viable and the other twin is miscarried.
A diagnosis of miscarriage based solely on slow rising or falling hCG levels has the possibility of being inaccurate.
Slow rising or falling hCG levels are normal toward the end of the first trimester, with levels rising more slowly and then reaching a peak around weeks 8-11, before they fall and level off for the rest of the pregnancy.
Care providers should recommended repeat tests, in conjunction with other tests such as pelvic exam and ultrasound.
Case For Second Opinions
The New Zealand woman who was told her pregnancy wasn’t viable had been referred for an ultrasound after her GP became concerned about her pregnancy.
The sonographer performed a transabdominal scan, and found no gestational sac, fetal pole or heartbeat. He didn’t offer the woman a transvaginal ultrasound, noting his belief the pregnancy wasn’t viable.
Following the ultrasound, the woman met with an obstetrician, a gynecologist and a midwife. She was told she had miscarried and was informed of the options available to her.
She chose to wait several days for the pregnancy to be expelled naturally, and to return for a dilation and curette (D&C) if this didn’t happen.
During this time, the woman was ‘very distressed’. She drank alcohol, ate unsafe foods, and took medications that could potentially cause harm to the baby, the NZ Health and Disability Commissioner was told.
After five days, the pregnancy hadn’t been expelled and she returned to have the D&C. She requested a final ultrasound because she still felt pregnant. Her doctor agreed, as her hCG levels had risen, which was consistent with an ongoing pregnancy.
The ultrasound found a viable embryo of 17.6mm. The D&C was not performed and her pregnancy continued.
The New Zealand Health and Disability Commissioner, Anthony Hill, released a report which found a sonographer and a radiologist were both in breach of the Code of Health and Disability Services Consumers’ Rights for services provided to the woman.
Mr Hill found the sonographer was incorrect in determining the pregnancy non-viable, based on one scan. He was also critical of the sonographer’s decision not to offer the woman a transvaginal ultrasound, and of the radiologist’s failure to report there had been no transvaginal scan.
What If I Am Given A Miscarriage Diagnosis?
No expectant parent wants to hear a much wanted pregnancy isn’t viable. It is very distressing, especially when health professionals are using clinical terms such as ‘missed abortion’ or ‘undetected heartbeat’.
If there is no heavy vaginal bleeding, and no clinical signs, there is something seriously wrong (such as an ectopic pregnancy). It’s advisable to wait a week, then perform further testing for a more definite diagnosis.
If your care provider gives you a diagnosis of miscarriage that you’re not comfortable with or your instincts tell you is wrong, or if the established guidelines for diagnosis haven’t been followed, then don’t hesitate to seek a second opinion.
With something as devastating as pregnancy loss, it’s normal you should want to feel absolutely certain of the diagnosis, before you make any decisions about treatment.
For more information on stillbirths or miscarriages, read our articles:
Stillbirth | What Expectant Parents Need To Know.
Support After A Miscarriage Or Loss
