The Difference Between Viable and Non-Viable Pregnancy
We know the statistics: between 10-20% of known pregnancies end in miscarriage. According to the March of Dimes, that number may be as high as 50% when we take into account pregnancies ending before a woman misses a menstrual cycle. It’s the difference between a viable and non-viable pregnancy; we’ll explore the terminology, causes and options to help achieve a healthy pregnancy and baby.
What does viability mean in pregnancy?
The term “viable pregnancy” comes from the word “vita,” which is Latin for “alive.”
In the first trimester of a pregnancy, “viable” means that a baby can be born alive.
What is a non-viable pregnancy?
A non-viable pregnancy means there is no chance of a live born baby. Depending on the stage of pregnancy, viability means different things.
Before 6 weeks, it can mean that Human Chorionic Gonadotropin (hCG) levels are increasing normally. hCG is a hormone produced by the placenta during its implantation process in the uterus.
After 6 weeks, a normal fetal heart indicates a viable pregnancy. A fetal heart with no heartbeat at any point is called fetal demise.
Before 22-24 weeks, a non-viable pregnancy is when a baby delivered has no chance of survival, even if there is still a heartbeat in the uterus.
- After 22-24 weeks, a viable pregnancy is when a baby has a chance to survive outside of the womb. However, some countries without adequate neonatal care consider non-viable at less than 26-28 weeks gestation.
Pregnancy is especially delicate in the first trimester, making it difficult to diagnose as viable or non-viable. These guidelines were developed to help define the ultrasound diagnosis of a non-viable pregnancy:
- Crown to rump length of > 6 mm and no heartbeat
- Mean sac diameter of > 24 mm and no embryo
- No fetal heartbeat >=2 weeks after a scan showed a gestational sac without a yolk sac
- No fetal heartbeat > 10 days after a scan showed a gestational sac with a yolk sac
What are the symptoms of a non-viable pregnancy?
On a technical level, the viability of a pregnancy can initially be measured by hCG levels. While a home pregnancy test can detect it in urine, the most accurate number comes from a blood test. The level should double every two or three days, and once it reaches 2000 mIU/ml, embryonic development should be visible on an ultrasound.
A chemical pregnancy becomes non-viable shortly after implantation. While hCG levels may initially be elevated, the pregnancy does not continue to develop and there are rarely any symptoms. Unless they’ve used assisted reproductive technology (ART), most women won’t even know they were pregnant.
If a pregnancy becomes non-viable later in gestation, however, there may be a variety of physical symptoms:
- Mild to severe cramps
- Pain in the back or abdomen
- White-pink mucus
- Passing tissue or clot-like material
- Loss of pregnancy symptoms such as nausea, though this can happen in a viable pregnancy too
Some women don’t learn their pregnancy is non-viable until they visit their doctor or midwife. By the 6th week of pregnancy, an ultrasound can determine whether there is a yolk sac within the gestational sac. It should also be able to pick up a fetal pole, the length of which is between the head (crown) and the bottom of the buttocks (rump) and is called crown-rump length. Finally, a healthy fetal heartbeat is a key factor in a viable pregnancy. Once it is seen, the risk of miscarriage drops significantly.
Can you have a non-viable pregnancy but no miscarriage?
Yes. In what is known as a missed miscarriage or missed abortion, a pregnancy can be non-viable and ultimately end without the body recognizing it. The placenta may continue to release hormones, resulting in continued signs of pregnancy. If it’s early enough in a pregnancy, in most cases the body will eventually expel the fetal tissue naturally. If the tissue remains, however, it can become dangerous and must be removed. In this case, a D&C procedure is done to remove the tissue and prevent infection. This will also allow the body’s hormonal levels to regulate back to normal.
What are the causes of a non-viable pregnancy?
Unfortunately, many different factors come into play when determining the viability of a pregnancy.
A chemical pregnancy, when the fertilized egg does not properly implant in the uterus.
An ectopic pregnancy, when the fertilized egg implants outside of the uterus, typically in a fallopian tube.
A molar pregnancy, when a tumor develops in the uterus at the beginning of the pregnancy as a result of a genetic error.
A blighted ovum, when the pregnancy stops after the gestational sac forms.
Abnormal chromosome count or congenital defects that prevent the baby from surviving.
- A birth that is so premature that the baby is unable to survive outside the womb.
Are there non-viable pregnancy options?
If you’ve experienced a non-viable pregnancy once, it doesn’t automatically mean that you can’t go on to have a healthy pregnancy in the future. You will be encouraged to wait between one to three menstrual cycles before trying for another pregnancy. After more than one miscarriage, however, it’s best to speak with your health practitioner. Further testing may be recommended, and you may ultimately consider assisted reproductive technology. Preimplantation genetic testing, for example, can be done during an IVF cycle to help determine the healthiest embryos and cut down on the risk of miscarriage.
Many women turn to egg donors and surrogates after recurrent pregnancy loss. Moving forward down this particular path to parenthood is often unexpected, but it can significantly increase the chances of building a family. In fact, the technology behind egg donation results in the highest rate of live birth success. If you’d like to learn more about your options, our team is here to advocate for you.