Objective: Despite lack of evidence for effectiveness, antepartum bed rest is prescribed by obstetricians for approximately 700,000 women per year. The lack of evidence would not be of concern if bed rest were a benign treatment. However, among non-pregnant populations, there is ample evidence that bed rest treatment produces serious adverse effects (Fortney, Schneider & Greenleaf, 1996; Sandler & Vernikos, 1986). These include reduced body fluids, plasma, red blood cell mass, muscle and bone mass, and altered carbohydrate metabolism. There is also emerging evidence of similar side effects among pregnant women (Maloni, Chance, Zhang, Cohen, Betts, & Gange, 1993; Maloni, Kane, Suen, & Wang, 2002, Maloni & Schneider, 2002 in press). Therefore the purpose of this study was to determine the pattern of maternal weight change over the duration of antepartum hospitalization for bed rest treatment and to determine whether infant birth weight was associated with maternal weight change. Design: This was a longitudinal repeated measures study. Population: The population was high-risk pregnant women who are prescribed antepartum bed rest in hospital. The convenience sample consisted of 147 pregnant women on antepartum hospital bed rest and their newborns. Women with a singleton gestation and a diagnosis of either preterm labor, premature rupture of membranes, incompetent cervix, placenta previa, or placental abruption were included. They were excluded if they had a pre-existing acute or chronic medical disorder such as hypertension. The setting was three university affiliated hospitals that provided tertiary care obstetric services in the Midwest, in both rural and urban settings. Data for this NIH funded study were collected between 1996 and 2001. Concepts: The concept studied was antepartum bed rest. The variables were maternal hospital weight gain, infant birth weight, and demographics. Methods: Maternal weight was obtained upon hospital admission and weekly using a standardized protocol. The weekly rate of weight change by Body Mass Index (BMI) was compared with Institute of Medicine (IOM) recommendations for pregnancy weight gain. Infant birth weight, obtained from the medical record, was compared with new US references for infant birth weight that are specific for gestational age, and also gender and race (Alexander, 1996). Findings: The majority of the sample were Caucasian (73%), married (58%), and had a high school education. Women were admitted to hospital between 21-33 weeks gestation (M=29.1, SD=2.9), primarily with the diagnosis of preterm labor or this plus another listed complication. The mean weekly rate of weight gain for women by BMI was consistently lower than IOM recommended weekly weight gains for pregnancy. Sixty-one percent of the sample either lost or gained no weight during the first week of hospitalization and 47% across the entire hospitalization (M=18.5 days, SD=13,69). Maternal weight change was not correlated with age, education, race, income, gravidity, previous neonatal death, stillbirth, or previous bed rest at home. The mean gestational age at birth ws 34.6 weeks (R=24.6-42.0). Infant birth weights ranged from 670 to 4125 grams. Infant birth weights were significantly lower than matched controls for the appropriate gestational age, gender, and race, from the national comparison reference group (t=7.09, P < .0000). Longer lengths of hospital bed rest were not associated with lower birth weights. Maternal weight change across hospitalizaton week significantly predicted infant gestational age at birth accounting for 10% of the variance (F=10.43, df 1, 94, p < .002). The weekly rate of maternal weight change for women whose length of hospital stay was limited to 14 days significantly predicted infant gesational age at birth accounting for 33% of the variance. Severity of obstetric risk did not predict gestational age at birth. Discussion: This is the first study to demonstrate maternal weight loss during antepartum bed rest and subsequent adverse infant outcomes. The cause of inadequate maternal weight gain during bed rest is unknown. However aerospace research provides extensive evidence to support mechanisms for both maternal weight loss and lower infant birth weight as a result of bed rest. Maternal weight gain, especially during the second and third trimester, is critical to fetal development. Lower sample infant birth weights are shocking as they occurred despite maternal "gold standard" treatment received in tertiary care obstetric facilities. Pregnancy bed rest does not appear to facilitate either maternal weight gain within IOM recommended limits or improved infant birth weight. Implications: The practice of prescribing antepartum bed rest to achieve or maintain maternal weight gain or to improve infant birth weight should be discontinued. Antepartum bed rest treatment is not only ineffective but also iatrogenic to both the pregnant women and her fetus.
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