What causes early pregnancy loss?

Updated: Nov 05, 2018
  • Author: Slava V Gaufberg, MD; Chief Editor: Jeter (Jay) Pritchard Taylor, III, MD  more...
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Embryonic abnormalities

Embryonic abnormalities account for 80-90% of first-trimester miscarriages. Note the following:

  • Chromosomal abnormalities are the most common cause of spontaneous miscarriage. More than 90% of cytogenic and morphologic errors are eliminated through spontaneous miscarriage.

  • Chromosomal abnormalities have been found in more than 75% of fetuses that miscarry in the first trimester.

  • The rate of chromosomal abnormalities increases with age, with a steep increase in women older than 35 years.

  • Trisomy chromosomes commonly are encountered, with trisomy 16 accounting for approximately a third of chromosomal abnormalities in early pregnancy.

Maternal factors

Maternal factors account for the majority of second-trimester miscarriages, with advanced age and a previous early pregnancy loss as the most common risk factors. [1] Chronic maternal health factors include the following:

  • Maternal insulin-dependent diabetes mellitus (IDDM): As many as 30% of pregnancies in women with IDDM result in spontaneous miscarriage, predominantly in patients with poor glucose control in the first trimester.

  • Severe hypertension

  • Renal disease

Acute maternal health factors include the following:

  • Infections (eg, rubella, cytomegalovirus [CMV], and mycoplasmal, ureaplasmal, listerial, toxoplasmal infections)

  • Trauma

Severe emotional shock may also cause first- and second-trimester miscarriages.

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