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PATIENT STORY

A 26-year-old woman gravida 3, para 2-0-0-2 at 30 weeks' gestation with routine prenatal care is concerned because her sister had a fetal demise at 34 weeks and she thinks her baby is moving less. A biophysical profile is performed, and the patient is reassured of normal fetal status (Figures 81-1, 81-2, 81-3, 81-4).

FIGURE 81-1

Ultrasound examination of a 27-week estimated gestational age (EGA) fetus showing measurement of the baby's humerus. (Reproduced with permission from E.J. Mayeaux, Jr., MD.)

FIGURE 81-2

Ultrasound examination of a 27-week estimated gestational age (EGA) fetus showing the baby's stomach (St), abdomen, spine (SP), and left portal vein (PV). (Reproduced with permission from E.J. Mayeaux, Jr., MD.)

FIGURE 81-3

Ultrasound examination of a 27-week estimated gestational age (EGA) fetus showing measurement of the baby's biparietal diameter (BPD). (Reproduced with permission from E.J. Mayeaux, Jr., MD.)

FIGURE 81-4

Ultrasound examination of a 27-week estimated gestational age (EGA) fetus showing all four chambers of the baby's heart. (Reproduced with permission from E.J. Mayeaux, Jr., MD.)

INTRODUCTION

Ultrasound in the third trimester of pregnancy is most often used to determine fetal number, presentation, and growth issues. This later pregnancy scan is also used to document fetal cardiac activity, placental location, and amniotic fluid volume, as well as provide a method for antenatal fetal assessment.

INDICATIONS FOR USE

  • A Cochrane review of 8 studies showed no difference in obstetric, antenatal, or neonatal morbidity between low-risk women undergoing routine late ultrasound examination after 24 weeks and those who did not.1 In addition, there was no difference in perinatal outcome measures, such as admission to a neonatal intensive care unit, birth weight less than 10th percentile, or perinatal mortality.

  • Hydrops fetalis is the accumulation of fluid in 2 or more fetal compartments, usually a result of immune pathologic conditions (Figure 81-5). Nonimmune hydrops will also be apparent on ultrasound and may be the result of severe anemias, congenital infections, heart or lung disease, chromosomal abnormalities, or fetal liver disease. Serial ultrasound examinations are useful for following pregnancies at risk for developing hydrops or to determine treatment. The middle cerebral artery peak-systolic velocity (MCA-PSV) is a noninvasive tool to predict fetal anemia.2 A 2009 systematic review provides compelling evidence that Doppler interrogation of the MCA-PSV performs well as a screening tool for severe fetal anemia of any etiology.3

  • Ultrasound may also be used to ...

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