40. Home Uterine Activity Monitoring RECOMMENDATION There is insufficient evidence to recommend for or against home uterine activity monitoring (HUAM) in high-risk pregnancies as a screening test for preterm labor, but recommendations against its use may be made on other grounds (see Clinical Intervention). HUAM is not recommended in normal-risk pregnancies. Burden of Suffering Preterm birth is a leading cause of perinatal morbidity and mortality in the U.S. Preterm neonates account for at least half of the mortality and morbidity among newborns without congenital anomalies.1 These conditions represent a leading cause of years of potential life lost before age 65.2 Preterm births generate large societal costs in providing neonatal intensive care and long-term treatment for complications.3 Both primary and secondary preventive measures have been proposed for the prevention of prematurity. Primary prevention includes efforts to reduce risk factors for prematurity, such as cessation of tobacco, alcohol, and other drug use, and programs to improve nutrition, socioeconomic conditions, and prenatal care. Secondary prevention involves the early detection and treatment of preterm labor. Accuracy of Screening Tests The rationale behind screening for preterm labor is the assumption that the risk of preterm birth can be reduced significantly by the prompt initiation of treatment (e.g., rest, hydration, tocolytic therapy). These measures are of potential value in prolonging pregnancy only in those cases involving idiopathic preterm labor and not in medically indicated preterm births (e.g., preterm rupture of membranes, antepartum hemorrhage, fetal distress). Tocolytic medications are generally ineffective after substantial cervical dilation (>2-3 cm) and effacement have occurred. Because patients and physicians may have difficulty in recognizing the early signs of preterm labor, many patients arrive at the hospital with advanced cervical dilation and effacement and/or with ruptured membranes. Such delays in detection are thought to limit the effectiveness of tocolysis. Screening for earlier detection of preterm labor has therefore been proposed. The principal screening tests are self-palpation and tocodynamometry. Programs to improve the early detection of preterm labor have centered on educating women about the symptoms of preterm labor and on teaching self-palpation to help them detect the increasing rate of uterine contractions which often precedes preterm labor.4 Studies of these measures have produced mixed results. Some studies have shown that self-palpation has poor sensitivity in detecting preterm labor. One study reported that only 15% of contractions were detected by patients and that fewer than 11% of pregnant women were able to identify half of their recorded contractions.5 Although tocodynamometry is usually performed in the hospital, home uterine activity monitoring (HUAM) has been advocated as an ambulatory screening test for preterm labor in high-risk women. The home tocodynamometer consists of a pressure sensor that is held against the abdomen by a belt and a recording/storage device that is carried by a belt or hung from the shoulder. Uterine activity is typically recorded by the patient for 1 hour, twice daily, while performing routine activities. The stored data are transmitted via telephone to a practitioner, where a receiving device prints out the data. Patients are often contacted by, or have access to, personnel who can address monitoring problems. The sensitivity and specificity of HUAM are uncertain, due to lack of data and the absence of a reference standard. External tocodynamometers, whether in the hospital or home, can produce inconsistent wave amplitudes when measuring uterine contractions, depending on the location of the instrument, the tension on the belt, thickness of adipose tissue, and other factors. Contractions of mild intensity can be confused with background noise. Studies suggest that HUAM performs similarly to monitoring devices used in the hospital, detecting 1.1-2.2 contractions for every contraction detected by conventional devices,6,7 and there is good correlation between HUAM results and contractions detected by intrauterine pressure catheters.8 There appears to be substantial variation among physicians in the interpretation of tocodynamometry tracings.7,9 Effectiveness of Early Detection A nonrandomized observational study10 and six randomized controlled trials11-18 of women at risk for preterm labor have compared birth outcomes with and without the use of HUAM. Three trials13,15,17 found no significant effect on the incidence of preterm birth or low birth weight, but sample size may have been inadequate to detect a difference. An observational study10 and four other trials14-16,18 reported a significant reduction in the incidence of preterm birth, neonatal morbidity and mortality, or low birth weight in pregnancies monitored by HUAM. In four of these studies,10,14,16,18 HUAM-monitored women received more intensive nursing or telemetry personnel contact than did women in the control groups, making it unclear whether it was the device or the nursing contact that was responsible for the improved outcome. Overall, the studies showing benefit also lacked randomization, had high attrition and exclusion rates, or suffered from other design limitations. Four studies10,11,14,16 found that HUAM-monitored women were less likely to experience preterm cervical dilation, effacement, or ruptured membranes and were more likely to be eligible for long-term tocolysis. Reported reductions in these surrogate measures, however, are of uncertain value in inferring an effect on clinical outcomes. The overall evidence shows rather consistently that the combination of HUAM and frequent provider telephone contact produces better outcomes than standard care. There are no known direct adverse effects from HUAM. The technology involves some inconvenience, and surveys suggest that some women reject the device because of its impact on their lifestyle.19 There is little evidence of other adverse effects. Studies have shown that HUAM-monitored women attend no more than one extra physician visit per pregnancy than do unmonitored women.10 Another theoretical adverse effect is unnecessary hospitalization or administration of tocolytic drugs to women who have abnormal home tocodynamometry data but are not in preterm labor. Objective evidence regarding the incidence of this problem is unavailable. Recommendations of Other Groups In 198920 and again in 1992,21 the American College of Obstetricians and Gynecologists concluded that HUAM should remain investigational and should not be recommended for routine clinical use. That position was maintained in a recent technical bulletin.21a In 1989, the National Institute of Child Health and Human Development concluded that the existing evidence was not convincing that HUAM, independent of vigorous nursing support and other interventions, was effective in assessing the risk of preterm labor or in preventing preterm birth.22 In a 1989 survey, 86% of the experts on an American Medical Association Diagnostic and Therapeutic Technology Assessment panel concluded that the effectiveness of HUAM was investigational, indeterminate, or unacceptable.23 In 1991, the Food and Drug Administration licensed the marketing of a HUAM device for women who have had a previous preterm delivery.24 A 1992 technology assessment by the Agency for Health Care Policy and Research concluded that current data did not support widespread use of HUAM or suggest its superiority over other methods for reducing the incidence of preterm births.25 Discussion The cost implications of HUAM are potentially great but have been incompletely evaluated in published research. Some studies have reported that average charges for HUAM-monitored women are $5,000-$11,000 lower than those for unmonitored women, presumably because of savings achieved by reduced neonatal intensive care.26-28 The cost-effectiveness of HUAM cannot fully be determined, however, until its clinical effectiveness has been demonstrated. Moreover, it remains unclear whether the money, personnel, and professional time required to provide this technology would divert resources from other potentially effective measures for the primary prevention of preterm births. CLINICAL INTERVENTION There is insufficient evidence to recommend for or against HUAM as a screening test for preterm labor in high-risk pregnancies (pregnancies with risk factors for preterm labor), but recommendations against its use may be made on other grounds, including its costs and inconvenience ("C" recommendation). HUAM is not recommended for normal-risk pregnancies (without risk factors for preterm labor) ("D" recommendation). Note: See also the U.S. Preventive Services Task Force background paper on this topic: U.S. Preventive Services Task Force. Home uterine activity monitoring for preterm labor. JAMA 1993;270:369-376. The draft of this chapter was prepared for the U.S. Preventive Services Task Force by Steven H. Woolf, MD, MPH, and Douglas B. Kamerow, MD, MPH. REFERENCES 1. Creasy RK. Preventing preterm birth. N Engl J Med 1992;325:727-729. 2. Centers for Disease Control and Prevention. Years of potential life lost before age 65_United States, 1990 and 1991. MMWR 1993;42:251-253. 3. Institute of Medicine. Preventing low birth weight. Washington, DC: National Academy Press, 1985. 4. Katz M, Newman RB, Gill PJ. Assessment of uterine activity in ambulatory patients at high risk of preterm labor and delivery. Am J Obstet Gynecol 1986;154:44-47. 5. Newman RB, Gill RJ, Wittreich P, Katz M. Maternal perception of prelabor uterine activity. Obstet Gynecol 1986;68:765-769. 6. Katz M, Gill PJ. Initial evaluation of an ambulatory system for home monitoring and transmission of uterine activity data. Obstet Gynecol 1985;66:273-277. 7. Hess LW, McCaul JF, Perry KG, et al. Correlation of uterine activity using the Term Guard monitor versus standard external tocodynamometry compared with the intrauterine pressure catheter. Obstet Gynecol 1990;76:52S-55S. 8. Paul MJ, Smeltzer JS. Relationship of measured external tocodynamometry with measured internal uterine activity. Am J Perinatol 1991;8:417-420. 9. Scheerer LJ, Campion S, Katz M. Ambulatory tocodynamometry data interpretation: evaluating variability and reliability. Obstet Gynecol 1990;76:67S-69S. 10. Katz M, Gill PJ, Newman RB. Detection of preterm labor by ambulatory monitoring of uterine activity: a preliminary report. Obstet Gynecol 1986;68:773-778. 11. Morrison JC, Martin JN, Martin RW, et al. Prevention of preterm birth by ambulatory assessment of uterine activity: a randomized study. Am J Obstet Gynecol 1987;156:536-543. 12. Iams JD, Johnson FF, O'Shaughnessy RW, et al. A prospective random trial of home uterine activity monitoring in pregnancies at increased risk of preterm labor. Part I. Am J Obstet Gynecol 1987;157: 638-643. 13. Iams JD, Johnson FF, O'Shaughnessy RW. A prospective random trial of home uterine activity monitoring in pregnancies at increased risk of preterm labor. Part II. Am J Obstet Gynecol 1988;159: 595-603. 14. Hill WC, Fleming AD, Martin RW, et al. Home uterine activity monitoring is associated with a reduction in preterm birth. Obstet Gynecol 1990;76:13S-18S. 15. Dyson DC, Crites YM, Ray DA, et al. Prevention of preterm birth in high-risk patients: the role of education and provider contact versus home uterine monitoring. Am J Obstet Gynecol 1991; 164:756-762. 16. Mou SM, Sunderji SG, Gall S, et al. Multicenter randomized clinical trial of home uterine activity monitoring for detection of preterm labor. Am J Obstet Gynecol 1991;165:858- 866. 17. Blondel B, Breart G, Berthoux Y, et al. Home uterine activity monitoring in France: a randomized controlled trial. Am J Obstet Gynecol 1992;167:424-429. 18. Morrison JC, Martin JN Jr, Martin RW, et al. A program of uterine activity monitoring and its effect on neonatal morbidity. J Perinatol 1988;8:228-231. 19. Chibber G, Cohen AW, Lindenbaum CR, et al. Patient attitude toward home uterine activity monitoring. Obstet Gynecol 1990;76:90S-92S. 20. American College of Obstetricians and Gynecologists. Strategies to prevent prematurity: home uterine activity monitoring. Committee on Obstetrics: maternal and fetal medicine. Opinion no. 74. Washington, DC: American College of Obstetricians and Gynecologists, 1989. 21. American College of Obstetricians and Gynecologists. Home uterine activity monitoring. Committee Opinion no. 115. Washington, DC: American College of Obstetricians and Gynecologists, 1992. 21a. American College of Obstetricians and Gynecologists. Preterm labor. Technical Bulletin no. 206. Washington, DC: American College of Obstetricians and Gynecologists, 1995. 22. Rhoads GG, McNellis DC, Kessel SS. Home monitoring of uterine contractility: summary of a workshop sponsored by the National Institute of Child Health and Human Development and the Bureau of Maternal and Child Health and Resources Development, Bethesda, Maryland, March 29 and 30, 1989. Am J Obstet Gynecol 1991;165:2-6. 23. Diagnostic and Therapeutic Technology Assessment (DATTA). Home monitoring of uterine activity. JAMA 1989;261: 3027-3029. 24. Fed Reg 1990 Oct 23;55:427-479. 25. Holohan T, Green I. Health technology review of home uterine monitoring. Rockville, MD: Agency for Health Care Policy and Research, 1992. (AHCPR Publication no. 92-0064.) 26. Morrison JC, Martin JN Jr, Martin RW, et al. Cost effectiveness of ambulatory uterine activity monitoring. Int J Gynecol 1989;28:127-132. 27. Morrison JC, Pittman KP, Martin RW, et al. Cost/health effectiveness of home uterine activity monitoring in a Medicaid population. Obstet Gynecol 1990;76:76S-81S. 28. Kosasa TS, Abou-Sayf FK, Li-Ma G, et al. Evaluation of the cost-effectiveness of home monitoring of uterine contractions. Obstet Gynecol 1990;76:71S-75S.