What Week Is the Highest Risk of a Miscarriage?

Medically Reviewed on 1/18/2023
The first trimester is associated with the highest risk for miscarriage.
The first trimester is associated with the highest risk for miscarriage.

Most miscarriages occur in the first trimester before the 12th week of pregnancy. A miscarriage in the second trimester (between 13 and 19 weeks) happens in 1% to 5% of pregnancies.

Early first-trimester pregnancy loss is defined as a nonviable intrauterine pregnancy with either an empty gestational sac or a gestational sac containing an embryo or a fetus without fetal heart activity within the first six to seven weeks of pregnancy. This means that a miscarriage may occur if pregnancy fails to progress due to either an empty gestational sac or a lack of fetal heart activity in an embryo. The incidence of a miscarriage in the first six weeks is as high as 31%.

  • The risk of a miscarriage decreases by 10% after the pregnancy crosses six weeks. Once fetal heart activity is established after six weeks, there is a decreased chance of failed pregnancy.

Early second-trimester pregnancy loss or late miscarriages occur after 13 and before 20 weeks of pregnancy. The incidence of second-trimester pregnancy loss is less than 1%.

Stillbirth or fetal death: Pregnancy loss that occurs at or after 20 weeks of pregnancy or at a weight of 350 grams (about ¾ of a pound) or greater is generally referred to as a stillbirth or fetal death. The approximate rate of stillbirth in the United States is 6 per 1,000 live births and stillbirths.

What is a miscarriage?

Miscarriage is a common experience.
About 10% to 20% of known pregnancies end in a miscarriage.

The loss of a baby within the first 20 weeks of pregnancy is called a miscarriage. When the unborn baby's weight is less than 400 grams and the baby dies, it is also considered a miscarriage. About 10% to 20% of known pregnancies end in a miscarriage; however, the actual figure may be higher. About 75% of women who have had three or four miscarriages will go on to have a successful pregnancy later.

A doctor or nurse may refer to a miscarriage as a spontaneous abortion. Abortion is a common medical name for all pregnancies that end before 20 weeks.

  • If a miscarriage occurs in the first 12 to 14 weeks of pregnancy, it’s referred to as an early miscarriage.
  • If pregnancy loss occurs after 14 weeks and up to 20 weeks of pregnancy, it’s referred to as a late miscarriage.


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What are the common causes of a miscarriage?

As per research, most early miscarriages are caused by abnormal chromosomes (structures that contain genetic information that we inherit from parents) of the developing baby (fetus) in the womb. It is common when the mother is older than 35. This means that women over the age of 35 years old who are having children are more likely to have a miscarriage. If the partner is older thane 45, the mother is more likely to have a miscarriage. Below are a few other causes of a miscarriage

Factor V Leiden: This blood-clotting genetic mutation has been found in studies to result in a lower live birth rate.

  • Even after three miscarriages in a row, more than 7 women out of every 10 will not have a miscarriage the next time around.

Other major and possible causes of a miscarriage include

Chromosomal abnormalities are one of the major causes of a miscarriage. Other causes include:

  • Maternal age
  • Uterine abnormalities
  • Hormonal irregularities
  • Infections such as herpes, syphilis, or listeriosis
  • Incompetent cervix (cervix dilates too early during pregnancy without pain or contractions)
  • Improper implantation of the fertilized egg in the uterine lining
  • Blighted ovum (embryo implants in the uterus but doesn’t develop into a baby)
  • Intrauterine fetal demise (embryo stops developing and dies)
  • Molar pregnancy (tissue in the uterus forms into a tumor)
  • Translocation (when part of a chromosome moves to another chromosome)
  • Septate uterus (band of muscle called septum divides the uterus into two sections)
  • Asherman syndrome (scars in the uterus that can damage the lining of the uterus)

Who is at a risk for a miscarriage? 18 Factors

18 Factors that may increase the risk of a miscarriage include

  1. History of two or more previous miscarriages
  2. Over the age of 35 years old
  3. Smoking
  4. Drinking alcohol
  5. Drug abuse
  6. Being exposed to harmful chemicals
  7. Autoimmune disorders such as systemic lupus erythematosus
  8. Obesity
  9. Hormonal problems such as polycystic ovarian syndrome (PCOS)
  10. Preexisting diabetes
  11. Thyroid problems
  12. Prenatal tests such as amniocentesis or chorionic villus sampling
  13. Caffeine consumption
  14. Congenital heart disease
  15. Severe kidney disease
  16. Severe malnutrition
  17. Radiation
  18. Certain medications such as Accutane (isotretinoin)

What are the signs and symptoms of a miscarriage?

Most women, especially during early pregnancy, will experience a miscarriage that is similar to heavy periods with slightly more cramping and bleeding than usual. It’s also common to have vaginal bleeding and pass large blood clots up to the size of a lemon. Heavy miscarriage bleeding can be scary or surprising, but it’s usually normal. Below are the common signs and symptoms of a miscarriage

Call the physician if you observe these symptoms of infection after a miscarriage

If there is a fever or severe abdominal pain, the abortion may become septic (infection of the cells of the uterus). This condition is a medical emergency.

How is a miscarriage usually treated?

Once a pregnancy has ended, there is nothing that can be done to prevent miscarriage from occurring.

  • Natural: Many women prefer to wait for the miscarriage to occur naturally. An incomplete miscarriage should happen within a week. A missed miscarriage may take longer to begin naturally (three to four weeks).
  • Medication: Women may prefer to take medication to ensure the miscarriage happens sooner rather than later. An incomplete miscarriage will usually be passed within six to eight hours of taking the medication. A missed miscarriage can happen quickly or may not happen for a few weeks. There are side effects that can occur with the medication, such as nausea and vomiting, chills, fever, and diarrhea. These effects usually only last for a few hours but can be distressing.
  • Surgery: In rare cases, women need surgery to remove the pregnancy tissue (called a dilation and curettage or D&C). This may happen in the case of a missed miscarriage if there is severe bleeding and pain or if the patient's preference is to avoid medication and they don’t wish to wait for a miscarriage to begin naturally. A surgery called D&C happens under general anesthesia and the surgery happens through the vagina. Like all surgical procedures, there are some risks involved such as infection, heavy bleeding (retained pregnancy tissue), damage to the cervix, and risks associated with anesthesia.

Patients may also be advised to take

  • Tylenol (acetaminophen) for cramps
  • Water for hydration
  • A balanced diet that is high in iron and vitamin C. Patients may be low in iron because of blood loss. Foods rich in iron include red meat, shellfish, eggs, beans, and leafy green vegetables. Foods high in vitamin C include citrus fruits, tomatoes, and broccoli. Doctors may also prescribe iron pills or a multivitamin.
  • Counseling in some cases

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Medically Reviewed on 1/18/2023
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