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Preconception Counseling, Genetics, and Prenatal Diagnosis

After an initial pregnancy resulted in a spontaneous loss in the first trimester, your patient is concerned about the possibility of this recurring. Which of the following is the most appropriate answer regarding the risk of recurrence after one miscarriage?

a. It depends on the genetic makeup of the prior abortus.

b. It is no different than it was prior to the miscarriage.

c. It has increased to approximately 50%.

d. It does not increase regardless of number of prior miscarriages.

e. It depends on the gender of the prior abortus.

The answer is b. An initial spontaneous abortion, regardless of the karyotype or gender of the child, does not change the risk of recurrence in a future pregnancy. The rate is commonly quoted as 15% of all known pregnancies.

A 24-year-old woman presents with a history of one first-trimester spontaneous abortion. Which of the following is the single most common specific chromosome abnormality associated with first trimester miscarriage?

a. 45 X (Turner syndrome)

b. Trisomy 21 (Down syndrome)

c. Trisomy 18

d. Trisomy 16

e. 46 XXY (Klinefelter syndrome)

The answer is a. Chromosomal abnormalities are found in approximately 50% of spontaneous abortions in the first trimester. Chromosome abnormalities become less common in advancing pregnancy, and are found in approximately one-third of second trimester losses and 5% of third trimester losses. Autosomal trisomy is the most common group of chromosomal anomalies leading to first trimester miscarriage. However, 45 X (Turner syndrome) is the most common single abnormality found.

A 29-year-old G3P0 presents to your office for preconception counseling. All of her pregnancies were lost in the first trimester. She has no significant past medical or surgical history. She should be counseled that without evaluation and treatment her chance of having a live birth is which of the following?

a. < 20%

b. 20% to 35%

c. 40% to 50%

d. 70% to 85%

e. > 85%

The answer is c. Miscarriage risk rises with the number of prior spontaneous abortions. Without treatment, the live birth rate approaches 50%. With treatment, successful pregnancy rates of 70% to 85% are possible ...

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