Report

The national infant mortality rate in the United States is one of the highest in Western industrialized countries, and diseases associated with premature births account for about one third of all the causes of these infant deaths.(1). Thus preterm labor is an important medical problem. The management of this condition includes risk assessment, detection, monitoring, and when deemed to be clinically indicated, the administration of one or more drugs that inhibit uterine smooth muscle contraction (tocolysis).(2-8). The three principal tocolytic agents currently used in the United States are ritodrine, terbutaline, and magnesium salts.

The increased uterine contractile activity that may be associated with preterm labor can be measured by a device called an external tocodynamometer(4). (Price P, Center for Drug Evaluation and Research, Food and Drug Administration, personal communication, 1991). These devices provide estimates of the frequency and duration of contractions as well as some indication of intensity. Because patterns or frequencies of low-grade uterine activity may serve as indicators of impending preterm labor, the use of external tocodynamometers to assess this risk and/or to diagnose such labor at an early stage has been an attractive concept. Manufacturers have developed portable monitoring devices suitable for home use that allow the transmission of digitized tracings over telephone lines to a remote site for interpretation. Thus, women at high risk for preterm labor can be monitored at home and the attending physician thereby provided information that may aid in the treatment of the patient. The Food and Drug Administration (FDA) has approved one of these devices, the Genesis home uterine activity monitoring (HUAM) system (manufactured by Physiologic Diagnostic Services), for use in detecting preterm labor in certain circumstances. The device is labeled for use in women with high-risk pregnancies, whose fetuses are of more than 24 weeks' gestation, and who have a history of preterm birth.

The clinical utility of home uterine monitoring is controversial. The American College of Obstetricians and Gynecologists has stated:

Thus, when the use of home uterine activity monitoring devices is part of a preterm birth prevention program, it has not been shown to add independently to the value of frequent provider-initiated phone contact. Electronic home uterine activity monitoring is still under study, but at this time it cannot be recommended for independent use in women at increased risk for preterm birth.(9).

A National Institutes of Health (NIH) workshop on "Home Monitoring of Uterine Contractility" was held in March 1989. The workshop summary included the following statement:

However, evidence that monitoring per se contributes importantly either to assessing the risk of preterm labor or to the prevention of preterm birth was felt by most participants to be less than fully convincing. It appears, therefore, that further work is needed both to optimize our ability to conduct home uterine activity monitoring, as well as to demonstrate unequivocally that, in its current form, it adds to our ability to prevent preterm birth.(10).

The senior NIH scientist at the workshop has indicated that the evidence regarding the effectiveness of home monitoring has not significantly changed since that conference was held (McNellis D, National Institutes of Health, personal communication, 1991). OHTA also sought the opinion of other experienced clinicians in the federal health care system. A senior official of the Maternal-Fetal Medicine Department, National Naval Medical Center, has indicated that simpler methods such as close monitoring of a patient at home by visiting nurses and/or by phone is sufficient to prevent preterm labor and that monitoring devices are not necessary (Thomas R, personal communication, 1991).

The FDA approval for marketing of a home uterine monitoring device was based on a multicenter clinical study which demonstrated that the device could detect uterine contractions indicative of the onset of preterm labor, utilizing cervical dilation as the primary endpoint.(11). In that study, Mou et al(12). selected patients believed to have an increased risk of preterm labor, based on a Creasy risk score of 10 or greater; 198 were randomized to a monitored group and 179 to an unmonitored group. The authors reported no statistically significant demographic or medical differences between the two groups. However, slightly greater proportions of unmonitored than monitored patients had histories of alcohol use (7.3 vs. 5.1), cocaine use (8.9 vs. 5.6), cigarette smoking (27.9 vs. 21. 2) and previous preterm birth (54.8 vs. 45, respectively). All patients received instruction in the signs and symptoms of preterm labor and in uterine self-palpation techniques. No regular health care professional-initiated telephone contact was scheduled for any patient. There was a significant difference in cervical dilation at the time of diagnosis of preterm labor between the study groups: mean dilation for the monitored group was 1.4 cm, and for the unmonitored group, 2.5 cm. The authors concluded that home uterine monitoring of high-risk pregnancies allows detection of preterm labor at an earlier stage of cervical dilation. Although not designated as study endpoints, a longer duration of gestation after diagnosis of preterm labor and a higher gestational week at delivery (36.6 vs. 34.9 weeks) were noted in the monitored group. In addition, the monitored group delivered infants of higher birth weights; those neonates had less need for intensive care, oxygen therapy, and mechanical ventilation. Assessments of cervical dilation were performed by "senior residents or attending physicians," but the accuracy and interobserver reliability of such measurements were not evaluated in this study. In addition, home monitoring was not directly compared with frequent provider-initiated patient contact, an approach that has been considered to be an intervention capable of reducing the incidence of preterm birth (vide supra).

Moreover, a group of clinician-researchers from several academic medical centers reviewed this study, as well as other pertinent studies of home uterine monitoring, and found the data wanting. They concluded that:

It is well known that assessment of cervical dilation is poorly ... We believe the scientific evidence is insufficient to warrant the clinical use of home uterine-activity monitoring except for research purposes... its so-called effectiveness relates not to the prevention of premature births but to the claim of earlier identification of premature labor, as evidenced by cervical dilation, with this system.... Home uterine-activity monitoring is a high-cost, ineffective approach to the all-important problem of prematurity. Daily contact, initiated by providers, is a lower-cost approach that is equally efficacious in preventing prematurity and should therefore be supported.(13).

Other published studies of home uterine monitoring techniques do not permit a determination that this technology results in improved treatment of preterm labor or a reduction in premature birth. Morrison et al(14). studied 67 patients at high risk for preterm labor who were randomly assigned to self-palpation or home uterine monitoring techniques. Patient care was managed by house officers supervised by attending staff. Subjects in the unmonitored group were contacted by telephone at least twice weekly. In this group of 33 patients, 22 (67) had documented preterm labor; of the 22,15 (68) were found to have cervical dilation of 3 cm or greater. In the monitored group of 34 patients, 24 (71) were diagnosed as having preterm labor. Two (8) of the 24 had 3 cm or more cervical dilation. The difference in gestational age at the time of diagnosis of preterm labor was significant, although the proportion of patients reaching 36 completed gestational weeks was significantly different in the control (55) and monitored (85) groups.

Iams et al(15). reported a 2-year study of 266 patients, randomly assigned to either labor education, self-palpation teaching, and daily telephone contact ("EP group") or to labor education, telephone contact, and home monitoring ("EM group"). Random assignment to the EP and EM groups with stratification for risk factors was not performed, and a significantly greater proportion of patients with multiple gestation were assigned to the EP group, which consequently may have led to a higher risk of preterm birth. Notwithstanding, there were no significant differences in rates of preterm labor or preterm delivery, mean birth weight, or gestational age at delivery between the groups. The authors concluded that frequent contact and symptom recognition are key in addressing the problem of preterm labor and in improving pregnancy outcome.

Dyson et al(16). evaluated 247 patients at risk for preterm labor, all of whom were provided an educational program addressing the recognition of preterm labor and self-palpation techniques at 24 weeks' gestation. Patients were then randomized to either a home monitoring (n=120) or education-palpation (n=127) group. All patients were contacted by a study nurse at least 5 days each week. A third group of 143 patients with the same risk factors who had delivered in that hospital during the preceding 30 months was designated a "standard care" group; attention was paid to selection of this group on the basis of risk factors and not pregnancy outcome. In singleton gestations, there was not a statistically significant difference in preterm births between the education-palpation and home monitoring groups. The incidence of preterm birth was significantly lower in the education-palpation than the standard care group; the monitored group was superior to the standard care group only for preterm births at less than 34 weeks. No significant differences between the education-palpation and home monitoring groups were noted for neonatal outcome in terms of birth weight, respiratory distress syndrome, intensive care admission, or infant hospital stay. For twin gestations (109 cases), the monitored group had fewer very low (<1500g) birth weight infants, fewer intensive care admissions, and shorter infant hospital stays than the education-palpation group. Both the education-palpation and monitored groups were superior to the standard care group in terms of the incidence of respiratory distress syndrome, intensive care admission, and neonatal death. The authors concluded that both education and home monitoring approaches are effective in improving the outcome in high-risk pregnancies; they believed that in twin pregnancies, home monitoring resulted in higher success rates for tocolytic therapy.

Other published studies have evaluated home monitoring with respect to detection of preterm labor, prevention of preterm birth, and cost and cost-effectiveness of this technology. These reports do not provide additional information sufficient to permit a logical and defensible conclusion as to the clinical effectiveness of home uterine monitoring.(17-20).

The American Medical Association conducted a Diagnostic and Therapeutic Technology Assessment (DATTA) review of home monitoring of uterine activity. With regard to the question of the effectiveness of this technology, 50 of the DATTA panelists surveyed believed it to be "investigational," and 32 believed it to be "indeterminate. " Only 14 classified effectiveness as "established."(21).

In sum, published data provide mixed support for the clinical utility of home uterine monitoring. Some studies did not compare the outcomes of monitored patients with those of clinically and demographically similar groups of unmonitored patients. Moreover, in prospective controlled studies, the unmonitored group was subject to a variety of alternative interventions, including education programs of varying intensity and provider-initiated telephone contact on variable schedules (e.g., from no such contact to a frequency as high as 5 days weekly). As a result, conclusions as to the effectiveness of HUAM must be tempered by the fact that this technique has not been adequately compared with simpler approaches applied with equivalent vigor. The opinions of experts and of professional and specialty groups tend to reflect these data. Therefore, while the use of HUAM devices may result in detection of preterm labor at an earlier stage of cervical dilation, it has not been established that use of this technology results in a reduction in the incidence of preterm birth, nor that it is superior to patient education coupled with frequent provider-initiated contact with patients.

Summary

The use of home uterine monitoring as a central element in programs directed at the prevention of preterm birth is highly controversial. Current published data do not clearly demonstrate it to be more effective than alternative, simpler methods nor provide adequate support to conclude that this technology is appropriate for widespread use, particularly in patient subsets other than those specified in the FDA-approved labeling of the HUAM device. Clinical studies directed at the determination of the effect of home uterine monitoring on net health outcome (e.g., diagnosis of preterm labor and reduction in premature births) in direct comparison with comparably intensive programs of education and provider-initiated contact should be encouraged. The FDA has stated that any claim for, or promotion of, the approved HUAM device "...that goes beyond the approved indication would be illegal and a cause for regulatory action by the FDA."(11).

References

1.

National Center for Health Statistics Advance report of final natality statistics Monthly Vital Statistics Report 1988 Vol. 39, No. 4, Suppl, Hyattsville, MD: Public Health Service, 1990.

2.

Beall MH, Edgan Edgar BW, Paul RH, et al. A comparison of ritodrine, terbutaline, and magnesium sulfate for the suppression of preterm labor. Am J Obstet Gynecol. 1985;153:854–859. [PubMed: 4073155]

3.

Caritis N, Toig G, Heddinger A, et al. Double blind study comparing ritodrine and terbutaline in treatment of preterm labor. Am J Obstet Gynecol. 1984;150:7–14. [PubMed: 6383045]

4.

Lam F, Gill PJ, Smith M, et al. Use of the subcutaneous terbutaline pump for long-term tocolysis. Obstet Gynecol. 1988;72:810–813. [PubMed: 3173932]

5.

Katz M, Robertsons Robertson PA, Creasy RK. Cardiovascular complications associated with terbutaline treatment for preterm labor. Am J Obstet Gynecol. 1981;139:605–608. [PubMed: 7468724]

6.

Laros RK, Kitterman JA, Heilbron DA, et al. Outcome of very low-birth weight infants exposed to beta-sympathetics in utero. Am J Obstet Gynecol. 1991;164(6 pt 1):1657–1664. [PubMed: 2048614]

7.

Ridgway LE, Muise K, Wright JW, et al. A prospective randomized trial comparison of oral terbutaline and magnesium oxide for the maintenance of tocolysis. Am J Obstet Gynecol. 1990;163:879–882. [PubMed: 2206076]

8.

Taslimi CK, Sibai BM, Amon E, et al. A national survey on preterm labor. Am J Obstet Gynecol. 1989;160:1352–1357. [PubMed: 2567573]

9.

American College of Obstetricians and Gynecologists American College of Obstetricians and Gynecologists, Committee Opinion, Committee on Obstetrics Maternal and Fetal Medicine No. 74 November 1989.

10.

Rhoads G, McNellis D, Kessel S. Summary of a Workshop: Home Monitoring of Uterine Contractility. National Institute of Child Health and Human Development. Am J Obstet Gynecol, in press. [PubMed: 1677235]

11.

Yin L. A response from the FDA. N Engl J Med. 1991;325:–. [PubMed: 1922242]

12.

Mou SM, Shirazali Sunderji GS, 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. [PubMed: 1951544]

13.

Sachs BP, Hellerstein S, Freeman R, et al. Home monitoring of uterine activity: Does it prevent prematurity? N Engl J Med. 1991;325:1374–1377. [PubMed: 1922241]

14.

Morrison JC, Martin JN, Martin RW, et al. Prevention of preterm birth by ambulatory assessment of uterine activity. Am J Obstet Gynecol. 1987;156:536–540. [PubMed: 3826196]

15.

Iams JD, Johnson FF, O'Shaugnessy RW. A prospective random trial of home uterine activity monitoring in pregnancies at increased risk of preterm labor. Am J Obstet Gynecol. 1988;159:595–603. [PubMed: 3421258]

16.

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. [PubMed: 2003537]

17.

Hill WC, Fleming AD, Martin RW, et al. Home uterine monitoring is associated with a reduction in preterm birth. Obstet Gynecol. 1990;76 (1 suppl):13S–18S. [PubMed: 2359574]

18.

Watson DL, Wech Welch RA, Mariona FG, et al. Management of preterm labor patients at home: Does daily uterine activity monitoring and nursing support make a difference? Obstet Gynecol. 1990;76 (1 suppl):32S–35S. [PubMed: 2359576]

19.

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 (1 suppl):71S–75S. [PubMed: 2113662]

20.

Morrison JC, Pittman KP, Marin RW, et al. Cost/health effectiveness of home uterine activity monitoring in a Medicaid population. Obstet Gynecol. 1990;76 (1 suppl):76S–81S. [PubMed: 2113663]

21.

Diagnostic and Therapeutic Technology Assessment: Home monitoring of uterine activity. JAMA. 1989;261:3027–3029. [PubMed: 2716135]

AHCPR Pub. No. 92-0064