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What Causes Miscarriage, Pregnancy Loss, or Stillbirth?

Knowing the facts can help
Knowing the facts can help
Istock/aabejon

You have recently experienced a pregnancy loss. You have many questions along with crushing sadness. Perhaps you miscarried, or perhaps your baby was stillborn. Whichever it may be, sadly, you lost your baby prior to birth. You are wondering if there was something you could have done to prevent it. You want to know more about what causes this to happen.

It is difficult to discuss a single cause of miscarriage, pregnancy loss or stillbirth in a simple way. There are many different causes for pregnancy loss and the causes are related to the stage of pregnancy in which the loss occurs.

In general, 20 – 25% of recognized pregnancies end in miscarriage, ectopic pregnancy, molar pregnancy, or stillbirth. In the United States, that makes about one million women a year experiencing pregnancy loss; it’s more common than you might think.

Abnormal Pregnancies – Ectopic and Molar Pregnancies

An ectopic pregnancy is when the fertilized egg implants somewhere other than the uterus, usually in the fallopian tube, less commonly in the stomach cavity, the ovaries or even the cervix. Ectopic pregnancies are usually caused by a blockage in the fallopian tube, from scarring or infection.

A molar pregnancy is when, at the time of egg fertilization, abnormal tissue develops, rather than a normal fetus. A molar pregnancy is caused by genetic error.

Neither an ectopic nor a molar pregnancy is viable for the fetus and both are dangerous for the mother.

Miscarriage During the First Trimester

During the first trimester, or before 12 weeks of gestation, as many as 40% of all pregnancies may end in miscarriage, often before the mother even knows she is pregnant.

First trimester miscarriage is most commonly caused by:

  • chromosomal abnormality, meaning that there is something wrong with the developing baby's chromosomes.
  • Infections
  • hormonal problems
  • external lifestyle influences such as smoking, substance abuse or radiation exposure
  • maternal trauma.

Miscarriage During the Second Trimester

Second trimester miscarriage, from around 13 to 19 weeks gestation, is less common than first trimester miscarriage, occurring in 1 to 5 percent of pregnancies.

The causes for second trimester miscarriage are often:

  • a chromosomal problem that actually occurred in the first trimester, but was undetected during normal first trimester screenings.
  • cervical insufficiency
  • external lifestyle influences such as smoking, substance abuse or radiation exposure
  • maternal trauma.

Stillbirth

When fetal death occurs after 20 weeks gestation, this tragedy is called a stillbirth. In the United States, a stillbirth occurs in about 1 in 200 pregnancies. Sometimes this is first diagnosed when the mother notices the baby moving around anymore. A visit to the doctor and an ultrasound test can detect whether or not the baby's heart is still beating. The most common cause for stillbirth is Sometimes it is never known what causes a stillbirth. However, the most common causes are:

  • birth defects in the developing fetus due to either chromosomal abnormalities
  • placental problems
  • poor fetal growth
  • infections
  • maternal health problems, such as pre-eclampsia
  • maternal trauma from an accident or domestic violence
  • umbilical cord accidents