What are the risk factors associated with hospital birth among women planning to give birth in a birth center in Washington State?

Background Few studies have evaluated risk factors associated with hospital birth among women planning to give birth in a birth center in the United States. This study describes the obstetrical risk factors for hospital birth among women intending to deliver in a birth center in Washington State. Methods We performed a retrospective cohort study of Washington State birth certificate data for women with singleton, term pregnancies planning to give birth at a birth center from 2004 to 2011. We assessed risk factors for hospital birth including demographic, obstetrical, and medical characteristics. We used multivariable logistic regression to estimate the odds ratio ( OR ) and 95% confidence interval ( CI ) of the association between risk factors and hospital birth. Results Among the 7118 women planning to give birth at a birth center during the study period, 7% (N = 501) had a hospital birth, and 93% delivered at a birth center (N = 6617). The strongest risk factors for hospital transfer included nulliparity ( OR 7.2 [95% CI 5.3‐9.8]), maternal age >40 years ( OR 3.7 [95% CI 2.1‐6.7]), inadequate prenatal care ( OR 3.7 [95% CI 2.7‐5.0]), body mass index ≥30 ( OR 2.1 [95% CI 1.6‐3.0]), government health insurance ( OR 9.3 [95% CI 5.0‐17.1]), and hypertension (10.1 [95% CI 5.7‐18.1]). Among nulliparous women, all of these demographic and obstetrical factors remained strongly associated with hospital birth. Conclusions This information may be useful for counseling women who plan a birth center birth about the risk of hospital birth.