What week is the highest risk of a miscarriage?

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 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 the 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, also known as spontaneous abortion, is a spontaneous loss of pregnancy before the 20th week. Half of  pregnancies may end in a miscarriage. Women who experience miscarriages may subsequently have a healthy pregnancy later.

What causes a miscarriage?

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?

Factors that may increase the risk of a miscarriage include

What are the signs and symptoms of a miscarriage?

Signs and symptoms of a miscarriage include

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

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Medically Reviewed on 9/29/2020
References
Medscape Medical Reference

March of Dimes


Cleveland Clinic


ACOG


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