Miscarriage Risk by Week – Plus Signs, Symptoms and Causes

Miscarriage is one of the biggest concerns among women who are pregnant or trying to get pregnant. Any pregnancy that ends on its own within the first 20 weeks of gestation is considered a miscarriage, so it’s easy to see why this topic is a difficult one for pregnant women to discuss.

If you’re pregnant or trying to get pregnant, you should know that 10% to 25% of all pregnancies end in miscarriage. While common, it’s not something to be concerned about, especially if you’re already past 13 weeks (more on that soon).

Between 50% and 75% of all miscarriages are what doctors call “chemical pregnancies,” or very early pregnancy losses. In these cases, pregnancy is lost shortly after the egg implants itself, which causes bleeding right around the time of your missed period. Many women don’t even realize that they had even conceived.

Naturally, you’re still concerned about the risks of having a miscarriage – that’s okay, it’s perfectly normal. We’re going to be looking at the risk of miscarriage by week for the first trimester as well as the symptoms of a miscarriage and factors that can increase your risk.

Miscarriage Rates by Week

Miscarriage Risk at Week 1-3

When you search for week-by-week miscarriage statistics, you may see some sites claiming that the risk of a miscarriage at 1-3 weeks is 75%. That can be terrifying to see as an expecting mother or a woman trying to get pregnant. But this number is misleading.

During weeks 1-3, you’re not actually pregnant yet. Using the 28-day cycle model, week 2 is when ovulation would occur. It’s estimated that implantation fails with one in three eggs, so there’s a higher probability for very early pregnancy loss (chemical pregnancy).

But if the egg implants itself, your risk of having a miscarriage decreases significantly.

Miscarriage Risk at Week 4-5: ~33%

During weeks four and five, you’ll likely find out that you’re pregnant (congratulations!). At this stage, there’s still about a 33% chance of a miscarriage, but with each passing day, that risk gets a little bit lower.

You may start experiencing some symptoms now, like bloating, fatigue, nausea and frequent urination. Your baby’s heart is pumping, most of its organs have formed, and leg and arm buds are starting to appear.

Miscarriage Risk at Week 6: 9.4%

By week 6, your risk of having a miscarriage drops to a very low level. Generally, miscarriage rates decline significantly between six and 10 weeks. As a general of thumb, doctors say that once the heartbeat is confirmed, chances of miscarriage are incredibly low.

With that said, it’s important to remember that women who are in their late 30s with or in their early 40s will be at an increased risk for miscarriage during the first trimester. Even after the fetal heartbeat is confirmed, miscarriage risks are still high for women 40 and older up to 12 weeks into the pregnancy.

The baby’s heart rate can also determine whether you’re at a greater risk of a miscarriage. A 1994 study showed that fetal heart rates under 100 had a much greater chance of ending in miscarriage at 6 weeks.

  • 90-99: 32%
  • 80-89: 64%
  • Under 80: 100%

Miscarriage Risk at Week 7: 4.6%

By week seven, your risk of having a miscarriage drops down to 4.6%. At this point, the embryo has doubled in size, but is still roughly the size of a small peanut. Your pregnancy hormones are raging, so morning sickness may be getting worse. On the other hand, you may feel like you’re hungry all the time.

Again, fetal heart rate will play a role in the risk of miscarriage at 7 weeks. Using the same data from the study above, heart rates:

  • Under 100: 100%
  • 101-109: 43%
  • 110-119: 18%
  • Under 120: 6.5%

Miscarriage Risk at Week 8: 1.5%

By the time you reach week 8, your risk of having a miscarriage declines to an extremely low level. You should be able to hear your baby’s heartbeat, and your doctor should give you an official due date.

Miscarriage Risk at Week 9: 0.5%

At this point, you’re chances of having a miscarriage are very slim. Your baby is continuing to grow, and putting more pressure on your bladder.

Miscarriage Risk at Week 10: 0.7%

Your chances decrease even further by week 10. At this stage, your baby is considered a fetus, and your pregnancy symptoms are really starting to kick in.

Miscarriage Risk at Weeks 11-12: ~0.7%

By weeks 11 and 12, your risks of miscarriage are still incredibly low. However, it is important to note that women who are in their late 30s and 40s may still be at an increased risk.

Here’s a breakdown of your risk of miscarriage by week 12 if you’re in your 30s and 40s:

  • 35-37: 2.8%
  • 37-39: 7.5%
  • 40+: 10.8%

By the time you reach the 12th week, your chances of miscarrying are incredibly low (unless you’re older). Remember, the vast majority of miscarriages take place within the first 13 weeks of the pregnancy.

Miscarriages can happen after 13 weeks, and up until week 28, they are considered miscarriages. If a pregnancy reaches 28 weeks and ends on its own, it’s considered a stillbirth.

Signs and Symptoms of a Miscarriage

If you’re pregnant and experience any of the symptoms below, please see your doctor immediately:

  • Back pain that’s mild or severe (more severe than menstrual cramps)
  • White-pink mucus
  • Weight loss
  • Red or brown bleeding that may or may not be accompanied by cramps
  • Tissue or clots passing from your vagina

In some cases, doctors can prevent miscarriages, so it’s important to see your doctor immediately if you’re experiencing any miscarriage symptoms.

Causes of Miscarriages

What can cause a miscarriage? What are the risk factors?

  • Hormonal issues
  • Infections
  • Lifestyle choices (smoking, drinking alcohol or drug use)
  • Trauma
  • Age
  • Improper implantation

If you’re pregnant, you’re undoubtedly concerned about having (or preventing) a miscarriage. But take heart in knowing that if it does happen, it’s common, and if you’ve already reached the 6-7 week mark, there’s a good chance that you won’t have a miscarriage. Nevertheless, it’s important to see your doctor if you’re experiencing any of the above symptoms or if you’re simply not feeling “right.”