How a Viable or Nonviable Pregnancy Is Diagnosed

Doctor using ultrasound on pregnant woman

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Receiving the diagnosis that your pregnancy is nonviable means that the fetus will not develop into a baby and/or can not survive outside the womb. This would likely be devastating news to hear, and you'd probably have many questions. First and foremost, you'd want to understand how doctors can know for sure that the pregnancy is nonviable.

Below, we look at how medical 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, unforeseen end to your pregnancy.

Overview

While the concept of a viable and nonviable pregnancy is relatively easy to grasp, it is governed by strict definitions. 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 or baby has no chance of being born alive.

Explicit diagnostic criteria have been designed to make clear when the termination of a nonviable pregnancy is warranted. Exacting, uniform standards are used to eliminate variation in how "reasonable chance of survival" is interpreted to ensure that the diagnosis of nonviable means the fetus has died and/or can't live outside the womb.

Experts have aimed to provide clarity about the diagnosis, not only from an ethical and legal standpoint, but to offer parents the assurance that they've made the right choice of treatment, including termination of the pregnancy, based on the weight of established medical evidence.

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 be able to survive (before 23 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

Extremely Premature Birth

In terms of premature birth, most hospitals look at viability from the perspective of when an infant has at least some chance of surviving. The line is drawn roughly around the 23rd to 24th week of gestation. Before 23 weeks of gestation, fetuses have around 1% or less chance of survival and high rates of morbidity. The outlook for survival improves steadily with each passing week of gestation.

Over the past 50 years, the prognosis for infants born between 23 and 28 weeks gestation has improved dramatically, with survival rates now between 50% to 70%. Premature infants born alive before 28 weeks often face extended stays in the neonatal intensive care unit (NICU) and many have lasting disabilities—but a growing number go on to thrive.

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

Determining Nonviability

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, as well as to prevent the termination of a potentially viable pregnancy.

Definitive Criteria

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 seven millimeters or more

Non-Definitive Criteria

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 day 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 five 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 seven 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 seven millimeters

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

Treatment

When pregnancy is nonviable, it will either miscarry on its own or a surgical procedure, such as dilation and curettage (D&C) or medication may be needed to remove remaining fetal tissue.

It's important to note that there are no treatments available or ways to save a nonviable pregnancy.

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.

Consult with your doctor 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

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.

A Word From Verywell

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

This is rare, but the possibility highlights the importance of the parents' full understanding and input at times when viability may be less than certain. Your doctor can advise you, but only you as parents can decide what is the most appropriate and loving choice for your baby.

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