How Doctors Diagnose Miscarriage

A Combination of Tests Confirm Pregnancy Loss

Man's hands on pregnant woman's stomach
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If you are experiencing signs of miscarriage (such as vaginal bleeding and abdominal cramping), it’s important that you see a doctor as quickly as possible. After assessing your clinical symptoms, the doctor will want to run a series of tests to determine what exactly is going on.

Miscarriage is commonly diagnosed using a combination of tests, the most standard of which include the hCG blood test, an ultrasound, fetal heart scanning, and a pelvic exam.

Quantitative hCG Blood Test

Human chorionic gonadotropin (HCG) is a hormone produced by the body during pregnancy. It becomes detectable in your about a week after ovulation when the fertilized egg implants in the uterus.

In the early weeks of pregnancy, the level of hCG can double every two to three days. When it is not increasing appropriately, this can often be an indication of a miscarriage. Almost invariably, falling hCG levels are enough to tell you that there's a problem. To confirm a diagnosis, doctors will need at least two hCG levels taken at least two days apart for results to be useful.

In early pregnancy, when the baby is too small to detect on an ultrasound, an hCG test may be the only tool available to confirm a miscarriage. While helpful in later pregnancy, the usefulness of an hCG test decreases as the pregnancy progresses. In fact, by the time a heartbeat is detectable, an ultrasound will be far more useful in evaluating the pregnancy.

Ultrasound Scans

Ultrasound machines use sound waves to get a rough image of the fetus and gestational sac. In early pregnancy, until around week eight, most practitioners will use a transvaginal ultrasound, which is inserted into the vagina, rather than an external abdominal ultrasound.

With the ultrasound, a miscarriage may be diagnosed under the following circumstances:

  • There are visible abnormalities or the lack of development of the gestational sac.
  • There is a lack of a fetal heartbeat that used to be there.
  • The embryo does not have a heartbeat when larger than five millimeters in size.

These parameters can vary and often need to be supported by additional tests.

Ultrasounds are not infallible and may be open to interpretation. Occasionally in early pregnancy, a single ultrasound may suggest that the fetus is not developing based on expectations of where it should be.

It could be, however, that ovulation occurred later in the menstrual cycle and that the pregnancy was not as far along as the doctor had believed. Even being off by a few days can make a difference in how an ultrasound is interpreted.

Fetal Heart Rate Monitors

Fetal heart rate monitors, sometimes called fetal dopplers, are handheld ultrasound devices which solely detect the sound of your baby’s heart through your abdomen. Typically speaking, the heartbeat becomes audible on a fetal monitor somewhere between week 7 and 12 of gestation. The exact time can vary based on the position of the uterus, the position of the placenta, and numerous other factors.

Doctors will often use a fetal heart monitor to help diagnose a miscarriage if a woman is in the latter part of her first trimester.

In the early stage of pregnancy, the lack of a heartbeat may not be considered conclusive of a miscarriage. By contrast, after 12 weeks, it is a strong indication of a pregnancy loss. A full ultrasound will typically be ordered if the fetal heartbeat cannot be found.

Pelvic Examination

A doctor may include a pelvic exam as a part of the diagnosis to check whether the cervix is dilating. A dilated cervix is usually a strong indication that a woman is miscarrying. If there is spotting or light vaginal bleeding and the cervix is not dilating, this may suggest a threatened miscarriage, a relatively common condition in which the pregnancy is still viable.

In most cases, the doctor will send the woman home and monitor her condition closely. Because spotting in early pregnancy is not uncommon, the doctor may choose to hold off additional testing unless the bleeding persists.

A pelvic exam may also reveal an ectopic pregnancy, a condition where the fertilized egg implants outside of the uterus. An ectopic pregnancy is considered nonviable and can become a medical emergency if left untreated.

A Word From Verywell

Vaginal bleeding and cramping during pregnancy don't necessarily mean that you're having a miscarriage. In most cases, you and your baby will be just fine, and you will deliver on time without any complications.

The main issue is not to ignore symptoms, even if you’re not absolutely certain about what you’re experiencing. Whatever the cause, minor or serious, it’s best to get it look earlier rather than later. Early diagnosis allows for early treatment and, in most cases, better outcomes.

Source:

Priesler, J.; Kopeika, J.; Ismail, L.; et al. "Defining safe criteria to diagnose miscarriage: prospective observational multicentre study." BMJ. 2015; 351:h4579.

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