August 4, 2020

Pregnancy Losses Are Most Commonly Chromosomally Abnormal

Pregnancy Losses Are Most Commonly Chromosomally Abnormal

Approximately 60% to 70% of pregnancy losses are most commonly chromosomally abnormal, whether as an isolated event (one) or recurrent which is considered to be two or more consecutive losses.

What are the most common chromosome abnormalities that cause miscarriage?

The most common chromosomal abnormality is Trisomy 16 which occurs in 26% of losses. Trisomy 16 is incompatible with life and has never been described progressing more than 11 weeks of gestation. The second most common chromosome abnormality in losses is monosmy X (45,X). It is estimated that 90% or 45,X conceptions spontaneously abort and 10% may go on to term delivery giving rise to little girls born with Turner’s Syndrome. The third most common chromosome abnormality in miscarriages is Trisomy 22 and the fourth is Trisomy 21. It is estimated that approximately 80% of Trisomy 21 pregnancies end in a miscarriage (pregnancy loss before 20 weeks of gestation) or intrauterine fetal demise (pregnancy loss after 20 weeks of gestation), while 20% may progress to term delivery.

The only noncontroversial parental cause of pregnancy loss is a known chromosome abnormality in the couple experiencing loss. Only 3% of individuals having three or more pregnancy losses have an inborn chromosome abnormality themselves which does not explain the over 60% of chromosomally abnormal losses. Most chromosome abnormalities in early pregnancy losses arise spontaneously either through non-disjunction or other genetic errors in gametes (egg or less likely sperm) or the early embryo.

What is a spontaneous miscarriage?

Spontaneous miscarriages are losses before the 20th week of gestation (pregnancy). It is the loss occurs before 10 weeks we consider the pregnancy to be developmentally an embryo. If the loss is after 10 weeks and before 20 weeks, it is  termed “fetus.” Regardless of the developmental stage, a loss is a loss. The joyous thoughts and feelings (and sometimes nausea) attributed to pregnancy can dissolve in an instant. It is important to know there are options to help overcome miscarriage and we can help.

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At Fertility Centers of New England, many patients come to us because they are struggling with infertility and/or miscarriages. We are proud to have helped thousands of patients realize their dream of becoming a parent. We want each of our patients to have the safest, healthiest pregnancy possible. If you have questions about your fertility or would like to set up a consultation, please contact us today.

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Joseph A. Hill, III, M.D.

Joseph A. Hill, III, M.D. Board-Certified in Reproductive Endocrinology and Infertility