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Late Miscarriage: What Are the Causes?

Miscarriage is a difficult, yet common (1 in 4) occurrence in early pregnancy. Early miscarriage usually happens due to fetal or embryo abnormalities, genetic and chromosomal abnormalities, exposure to certain toxic substances or medications the mother took prior to realizing she was pregnant. Early miscarriage is the term which describes loss of pregnancy prior to the 13th week of pregnancy, or first trimester.

Late miscarriage is particularly heartbreaking. As late miscarriage occurs between the 13th and 20th week of pregnancy most parents-to-be witnessed their baby moving about the uterus via ultrasound, and possibly felt the kicks themselves. Many have at least a few baby items purchased and ready to go. The mom-to-be is possibly displaying a developing bump and the news was already shared with family and friends.

Once the devastation and shock of late miscarriage ebbs parents begin to question “Why?”. Here we’ll take a look at some of the most common causes of late miscarriage. Each pregnancy is different as is each miscarriage. By understanding the cause of your heartbreaking loss, your physician will know the steps you both need to take to avoid the same devastating outcome the next time.

Causes of Late Miscarriage

There are several factors which cause late miscarriage including some of the same ones that lead to early miscarriage. The most common cause of any miscarriage, early or late, is a fetal abnormality or a problem with the baby’s development. Of course, developmental and chromosomal abnormalities are usually evident in an ultrasound. There are other causes particular to miscarriage later in pregnancy. The most common ones are:


Cervical Insufficiency

(Also called “incompetent cervix”) Prior to pregnancy you have a closed and firm cervix. As your pregnancy progresses and your due date draws near your cervix begins to soften, shorten and open. With cervical insufficiency your cervix opens too soon. This causes the baby to be born prematurely.


Cervical insufficiency is a common factor in late miscarriage, however most women don’t realize it until they lose the pregnancy. Known risks for this condition are:


  • Trauma to the cervix such as a surgical procedure used to treat cervical abnormalities uncovered from an exam or Pap smear. A previous D&C may cause a weakened cervix. Sometimes the cervix tears during a previous delivery and causes weakening to the cervical tissues.


  • Congenital conditions that affect the body’s connective tissue, including the tissue of the cervix, may result in cervical weakness. Women exposed in-utero to DES, a synthetic estrogen often prescribed to mothers in the 60’s and 70’s to control morning sickness, are at risk for cervical complications including cervical insufficiency. (Note: In 1971 the U.S. banned DES. However, other countries continued using DES until at least the early 80’s.)


  • Race seems to be a factor in cervical insufficiency. Black women have a higher risk for cervical insufficiency than other races.


Congenital Defects

Congenital birth defects are those which are most likely inherited, but they can also occur due to exposure to certain toxins, medication or chemicals during pregnancy. A congenital birth defect may also be the result of an infection during pregnancy. If the fetus develops severe heart, lung or brain birth defects it can become nonviable and often dies in-utero.


Placental Problems

Placental abruption occurs when the placenta separates from the uterine wall. The placenta provides all of the nutrients and oxygen necessary for the developing fetus. Once it detaches the fetus no longer receives sustenance.



Certain infections cause issues that factor into late miscarriage, though more often in developing countries and less frequently in the U.S. These include:


  • Bacterial Vaginosis
  • Chlamydia
  • Gonorrhea
  • Trichomoniasis
  • Viral Vaginitis


Abdominal Trauma

Though less common than other causes, certain traumas to the abdomen, such as an auto accident, fall or sustained blow to the abdominal region, can result in a late miscarriage.


Drug and Alcohol Use

Of course, as soon as you begin trying to conceive you should already practice a healthy lifestyle. Certain drugs, especially cocaine and methamphetamines, are very closely associated with late miscarriage. Illegal drugs cause low birth weight, placental abruption, preterm birth and fetal death. Cigarettes contribute to late miscarriage and alcohol poses a very high risk for fetal abnormalities and death throughout pregnancy.

According to a recent study by the University of Copenhagen, even one or two alcoholic beverages per week increase the odds of late miscarriage by 70%.


Medical Conditions Related to Late Miscarriage

Women who have certain chronic medical conditions are at a higher risk for late miscarriage. This risk is much higher if the condition is poorly controlled with lifestyle and medication. Depending on the severity some severe medical conditions pose an inherent risk for late miscarriage no matter how controlled. Examples of chronic conditions which increase your risk for pregnancy loss are:


  • Autoimmune diseases; always consult your physician before trying to conceive.
  • Diabetes
  • Hypertension (high blood pressure)
  • Thyroid disease and disorders
  • Polycystic ovarian syndrome (PCOS)
  • Hormonal imbalances



Genetic abnormalities and autoimmune disorders such as lupus contribute to thrombophilia risk. Thrombophilia puts you at an increased risk for developing blood clots which poses a threat to your placenta and umbilical cord and can interfere with the development of your baby.


Unknown Causes of Late Miscarriage

As distressing as it is, there is often no known cause for late miscarriage. This adds to the heartache of pregnancy loss. Without knowing the reason, your physician will see any future pregnancies as high risk and your odds for another miscarriage increase.


If You’re Concerned Reach Out to Us

If you experienced a late miscarriage or have concerns, consult with the compassionate professionals at LA IVF. There are options available to ensure a safe and healthy pregnancy. For more information contact our office.

TEL: 310-286-2800 | FAX: 310-691-1116