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A 22-year-old woman presents with no menstrual period for approximately 2 months (she has irregular menses.) She is complaining of morning sickness but is otherwise feeling well. A urine pregnancy test confirms she is pregnant. Figure 77-1 shows a fetus of 9 weeks estimated gestational age (EGA).

Figure 77-1

Ultrasound examination of a fetus of 9 weeks estimated gestational age. The ultrasound was performed with a vaginal probe and the membranes are visible. (Courtesy of E.J. Mayeaux, Jr., MD.)

Obstetrical ultrasound has become a vital tool in our ability to properly care for the pregnant patient. Vast technologic improvements have made visualization of the pregnancy even better and improved our diagnostic capabilities, ranging from the normal pregnancy to the extremely early ectopic pregnancy. Ultrasonography (US) allows for a relatively detailed assessment of fetal gestational age, development, number of fetuses, and anatomy in utero. Most pregnancies in the United States undergo ultrasound imaging for various indications.

  • Women who receive antenatal care have lower maternal and perinatal mortality and better pregnancy outcomes.1 However, the optimal components of prenatal care have not been rigorously examined in well-designed studies.
  • In the United States in 2003, 84.1% of pregnant women obtained prenatal care in the first trimester, and only 3.5% received no care or initiated prenatal care in the third trimester.

  • Ultrasound is used to estimate gestational age and to calculate the expected date of delivery (EDD). Ultrasound is especially helpful when menses are irregular, the last menstrual period (LMP) is unknown, or in patients who conceived while using hormonal contraceptives. A Cochrane review noted with more accurate dating there was a reduction in intervention for postterm pregnancy.2
  • The Routine Antenatal Diagnostic Imaging with Ultrasound (RADIUS) trial was a randomized trial of routine obstetrical ultrasound screening.3 It included more than 15,000 women in the United States. The trial showed that routine ultrasound screening was associated with a significantly increased detection of fetal anomalies, but no improvement in any perinatal outcome, including mortality, preterm birth, birth weight, and neonatal morbidity.
  • First trimester vaginal bleeding is found in 20% to 40% of pregnancies. The differential diagnoses include possible spontaneous abortion, ectopic pregnancy, and gestational trophoblastic disease.
  • Ectopic pregnancy causes a significant degree of morbidity and mortality if untreated, often through tubal rupture with potentially life-threatening hemorrhage. Identification of an intrauterine pregnancy effectively excludes the possibility of an ectopic in almost all cases, unless conception involved assisted reproductive technology.
  • Threatened, inevitable, incomplete, or complete spontaneous abortion may cause first trimester bleeding. Up to one-third of recognized pregnancies end in early pregnancy loss. Ectopic pregnancy may also be a concern. US may be used to determine if a gestational sac or yolk sac is present in the uterus.
  • First trimester transvaginal ultrasound used in conjunction with serum screening is the most sensitive noninvasive technique to detect aneuploidy. ...

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