How Do You Diagnose a Nonviable or Viable Pregnancy?

A viable pregnancy means that a fetus can survive gestation and childbirth. If your pregnancy is nonviable, it means that the fetus will not develop into a baby or can't survive outside the uterus.

Learning that your pregnancy is not viable is devastating, and you'll probably have many questions. First and foremost, you'll want to understand how health care providers can know for certain that the pregnancy isn't progressing.

Learn more about how health care providers diagnose this condition, common causes, treatment options, and how it differs from miscarriage. We also explore the impact a nonviable pregnancy may have on your fertility, and how to cope with this heartbreaking end to your pregnancy.

Viable vs. Nonviable Pregnancies

From a clinical perspective, a viable pregnancy is one in which the baby can be born and have a reasonable chance of survival. By contrast, a nonviable pregnancy is one in which the fetus has no chance of survival.

Explicit diagnostic criteria have been designed to make clear when the termination of a nonviable pregnancy is warranted. Exacting, uniform standards ensure that the diagnosis of nonviable means the fetus has died or can't live outside the uterus.

Causes of a Nonviable Pregnancy

From a diagnostic perspective, nonviable does not mean a little chance of survival. It means no chance of survival. The most common reasons for this include:

• A baby born too prematurely to survive (before 22 weeks)
• A congenital defect that makes the survival of the fetus outside of the uterus impossible
• A pregnancy in which the fetus no longer has a heartbeat
• Anembryonic gestation, also known as a blighted ovum, in which the pregnancy stops growing after the gestational sac forms
• Ectopic pregnancy, in which the fertilized egg implants outside of the uterus
• Molar pregnancy, in which a fertilized egg incapable of survival implants in the uterus

Viability After an Extremely Premature Birth

Most hospitals consider viability in terms of premature birth from the perspective of when an infant has at least some chance of surviving. The line is drawn roughly around the 22nd to 24th week of gestation.

Before 22 weeks

Before 22 weeks of gestation, fetuses have less than a 1% chance of survival and high rates of morbidity. There is no known record of a baby born at 20 weeks or earlier surviving. The outlook for survival improves steadily with each passing week of gestation.

Over the decades, rates of survival before 23 weeks have barely budged. The earliest known birth with a surviving infant is at 21 weeks. Before 23 weeks, the fetus often dies at birth or shortly thereafter, despite medical intervention.

23-28 weeks

Over the past 50 years, the prognosis for infants born between 23 and 28 weeks gestation has improved dramatically. In 2015, research found survival rates between 50% to 70%.

Premature infants born alive before 28 weeks often face extended stays in the neonatal intensive care unit (NICU). While many have lasting disabilities, a growing number go on to thrive.

For those extremely premature infants that survive birth, parents and health care providers will decide together which life-sustaining treatments are appropriate or feasible.

Determining Nonviability in a Pregnancy

Beyond an extremely premature birth, the Society of Radiologists in Ultrasound (SRU) has established definitive criteria to establish nonviability.

This determination is meant to ensure that providers and patients are clear on when a pregnancy is viable or not. It also helps prevent the termination of a potentially viable pregnancy.

Definitive criteria for a nonviable pregnancy

Using ultrasound, a pregnancy is declared nonviable based on the following definitive criteria:

• A gestational sac that contains no embryo but has a mean diameter of 25 millimeters or greater
• A gestational sac with a yolk sac is observed in a scan but 11 or more days later, there is no embryo with a heartbeat
• A gestational sac without a yolk sac is observed in a scan but two or more weeks later, there is no embryo with a heartbeat (this means the pregnancy has stopped progressing)
• No fetal heartbeat and a crown-to-rump length of 7 millimeters or more (though this could be operator-dependent with a reasonable margin of error)

Non-definitive criteria for a nonviable pregnancy

In some circumstances, a pregnancy may be considered potentially nonviable and require further testing. According to SRU guidelines, a pregnancy would be considered at risk of nonviability based on the following non-definitive criteria:

• A gestational sac with a yolk sac is observed, but seven to 10 days later, there is no embryo with a heartbeat
• A gestational sac without a yolk sac is observed, but seven to 13 days later, there is no embryo with a heartbeat
• Absence of an embryo six or more weeks after the last menstrual period
• Disproportionately small gestational sac in relation to the embryo (less than 5 millimeters difference between the mean sac diameter and the crown-to-rump length)
• Empty amnion (the membrane meant to surround the embryo)
• Enlarged yolk sac of greater than 7 millimeters
• No embryo and a mean gestational sac diameter of 16 to 24 millimeters
• No heartbeat and a crown-to-rump length of fewer than 7 millimeters

In the vast majority of these cases, these pregnancies will ultimately be determined nonviable.

Treatment for a Nonviable Pregnancy

When pregnancy is nonviable, it might miscarry on its own. If it doesn't, you may need a surgical procedure, such as dilation and curettage (D&C), or medication to remove remaining fetal tissue.

In many cases, having a nonviable pregnancy will not adversely impact future fertility. Often, nonviable pregnancies occur due to chromosomal or other abnormalities that do not indicate a lasting fertility issue.

One possible risk occurs with an ectopic pregnancy that is not diagnosed before potential complications arise, which can result in a rupture of the fallopian tube or another ectopic location.

Consult with a health care provider about your particular circumstances to get an accurate read on how your nonviable pregnancy may or may not affect your chances of having a healthy pregnancy in the future.

Coping With a Nonviable Pregnancy

In addition to tending to any physical recovery needed after a nonviable pregnancy, be sure to attend to your emotional healing as well. Coping with pregnancy loss can take a big toll and may require attention and care for your mental health.

Give yourself time to grieve. It can help to find a compassionate person to talk to, such as a partner, relative, friend, or therapist.

Guidelines on nonviability prevent the misdiagnosis of a viable pregnancy. It's important to remember, however, that viable pregnancy doesn't necessarily mean perfect health. In some cases, a baby may be able to survive outside of the womb but will require intensive lifelong medical intervention.