Threatened Miscarriage

Excerpt

A pregnancy loss or "miscarriage" generally is defined as pregnancy failure before 20 weeks of gestation. A threatened miscarriage also called a "threatened abortion" or "threatened early pregnancy loss," typically refers to vaginal bleeding and uterine cramping in an otherwise viable pregnancy before 20 weeks of gestation, though more commonly occurring in the first trimester. A viable pregnancy is a pregnancy with the potential outcome of a live birth. First-trimester vaginal bleeding and cramping are also common symptoms of early pregnancy loss and incomplete miscarriage. However, characteristic clinical findings of a threatened miscarriage are a closed cervical os, without passage of products of conception, and no evidence of fetal or embryonic demise on pelvic ultrasound.

Approximately 25% of pregnancies have some degree of vaginal bleeding during the first trimester, and approximately half of these patients progress to early pregnancy loss. The bleeding during a threatened miscarriage is typically mild to moderate; heavier bleeding that is more than typical menstrual flow is associated with an increased risk of pregnancy loss. Intermittent cramping, suprapubic pain, pelvic pressure, or lower back pain are also common.

Evaluation of threatened miscarriage depends on the pregnancy's gestational age. At early gestational ages, it is important to establish the location of the pregnancy to rule out an ectopic pregnancy, which can also present with vaginal bleeding and lower abdominal pain. Once an intrauterine pregnancy has been established, the clinician must determine the viability of the pregnancy, which is accomplished through a pelvic examination and ultrasound. If fetal cardiac activity is not seen, serial ultrasound examinations may be required to differentiate an early viable pregnancy from a pregnancy loss.

Historically, the term "abortion" has been used to refer to any pregnancy loss before 20 weeks, though many leading professional organizations now recommend using variations of the terms "miscarriage" or "pregnancy loss" (eg, threatened miscarriage, threatened pregnancy loss) as patients prefer these terms.