he World Health Organization conducted a multicenter randomized trial with almost 25,000 women comparing routine prenatal care with an experimental model designed to minimize visits (Villar, 2001). In the new model, women were seen once in the irst trimester and screened for certain risks. hose without anticipated complications-80 percent of those screened-were seen again at 26, 32, and 38 weeks. Compared with routine prenatal care, which required a median of eight visits, the new model required a median of only ive. No disadvantages were attributed to the regimen with fewer visits, and these indings were consistent with other randomized trials (Clement, 1999; McDuie, 1996).
At each return visit, the well-being of mother and fetus are assessed (see Table 9-1). Fetal heart rate, growth, and activity and amnionic fluid volume are evaluated. Maternal blood pressure and weight and their extent of change are examined. Symptoms such as headache, altered vision, abdominal pain, nausea and vomiting, bleeding, vaginal luid leakage, and dysuria are sought. Mter 20 weeks' gestation, uterine examination measures size from the symphysis to the fundus. In late pregnancy, vaginal examination often provides valuable information that includes conirmation of the presenting part and its station, clinical estimation of pelvic capacity and configuration, amnionic luid volume adequacy, and cervical consistency, efacement, and dilatation (Chap. 22, p. 435).
Between 20 and 34 weeks' gestation, the height of the uterine fundus measured in centimeters correlates closely with gestational age in weeks Gimenez, 1983). his measurement is used to monitor fetal growth and amnionic fluid volume. It is measured along the abdominal wall from the top of the symphysis pubis to the top of the fundus. Importantly, the bladder must be emptied before fundal measurement (Worthen, 1980). Obesity or the presence of uterine masses such as leiomyomas may also limit fundal height accuracy. Moreover, using fundal height alone, fetal-growth restriction may be undiagnosed in up to a third of cases (American College of Obstetricians and Gynecologists, 2015b; Haragan, 2015).
Instruments incorporating Doppler ultrasound are often used to easily detect fetal heart action, and in the absence of maternal obesity, heart sounds are almost always detectable by 10 weeks with such instruments (Chap. 10, p. 213). he fetal heart rate ranges from 11e0 to 160 beats per minute and is typically heard as a double sound. Using a standard nonampliied stethoscope, the fetal heart is audible by 20 weeks in 80 percent of women, and by 22 weeks, heart sounds are expected to be heard in all (Herbert, 1987). Because the fetus moves freely in amni onic fluid, the site on the maternal abdomen where fetal heart sounds can be heard best will vary.
Additionally, with ultrasonic auscultation, one may hear the unic soule, which is a sharp, whistling sound that is syn chronous with the fetal pulse. It is caused by the rush of blood through the umbilical arteries and may not be heard consistently.
In contrast, the uterine soule is a soft, blowing sound that is synchronous with the maternal pulse. It is produced by the pas sage of blood through the dilated uterine vessels and is heard most distinctly near the lower portion of the uterus.