176784 Safety of planned out-of-hospital birth similar to low-risk hospital birth in California: A large retrospective cohort study

Monday, October 27, 2008: 2:35 PM

Peter Schlenzka, PhD , Private Consultant, Aptos, CA
Kenneth C. Johnson, PhD , Department of Epidemiology and Community Medicine, University of Ottawa, Ottawa, ON, Canada
Betty-Anne Daviss, MSc, RM , Midwifery Collective of Ottawa, Ottawa, ON, Canada
     
Many obstetrical societies claim that the hospital-based obstetric approach to childbirth is safer with respect to perinatal mortality than the natural approach to childbirth as administered by midwives and some physicians in free-standing birth centers or at home, but the scientific evidence does not support that view.

The objective of the study was to compare perinatal risk for low-risk births in hospital with planned out-of-hospital births. From 1,147,859 births in a merged birth certificate and hospital discharge database for California for 1989-1990, 806,402 low risk hospital births, (pregnancies that could be considered candidates for natural childbirth), 9,525 planned free-standing birth centre births and planned homebirths were identified, with a comprehensive risk profile for each pregnancy. Intrapartum and postpartum transfers to the hospital were allocated to the originating birth setting. Perinatal mortality was compared with two statistical approaches: indirect standardization using only birthweight, sex, race, age, education, and insurance as risk adjusters, and logistic regression controlling for all risk factors available in the database.

Both the indirect standardization and the logistic regression analyses found that low-risk women who opted for a natural childbirth in an out-of-hospital setting (including the unfavorable results for transfers from home to hospital) experienced a slightly though not significantly lower perinatal mortality than low-risk women who opted for a hospital birth. These analyses in California do not support the claim by the obstetric profession that for the large majority of low-risk women hospital birth is "safer" with respect to perinatal mortality.

Ethical Issues: Study received Stanford University ethical approval. Funding Source: none

Learning Objectives:
1. Identify 3 reasons why in most studies it is usually difficult to evaluate the differences in risk between home and hospital birth. 2. Describe 3 reasons why this particular study is so important for comparing homebirth to hospital birth perinatal risk. 3. Articulate how the perinatal mortality results of this study compare with those of other North American studies of homebirth.

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: Kenneth C. Johnson, PhD is a senior epidemiologist with the Public Health Agency of Canada. He has worked in chronic disease epidemiology for more than 25 years. His risk assessment work has focussed on cancer risks related to passive smoking, chlorination by-products in drinking water, physical activity and diet. His interest in perinatal epidemiology has continued since he ran the Canadian birth defects registry in the late 1980s, and had a fellowship at the National Perinatal Epidemiology Unit, original home of the Cochrane Collaboration. He has written on limitations of randomized controlled trials in perinatal research and last year published a prospective cohort study on more than 5,400 intended home births. He holds adjunct professorships in epidemiology at the University of Ottawa, Queens and the University of Western Ontario.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.

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