We describe the first report in Japan of a woman who received omalizumab during pregnancy and delivery. Her asthma was so severe that she had been taking systemic corticosteroids since 22 years old, but asthma was poorly controlled. She had been pregnant seven times before, but almost every time asthma control had worsened and spontaneous abortion resulted, so she had only one child. She confirmed that she was not intending to become pregnant, and initiated use of omalizumab in August 2009. However, pregnancy was identified after she had taken the drug 3 times. We explained the risks in detail, but the patient wanted to keep taking omalizumab, as her asthma control was improved and she thought she could continue the pregnancy. We therefore decided to continue with omalizumab therapy. In October, she caught a cold and experienced asthma exacerbation. Despite the risk, she decided to suspend omalizumab therapy after taking the drug 7 times, as she was not feeling any benefit from therapy. Threat of abortion was identified in February 2010, so a 544-g female baby was delivered at 26 weeks gestation by Cesarean section. The baby had to be hospitalized in the neonatal intensive care unit because of low birth weight, but she has been developing and growing without handicap. We report this case as the first known case of pregnancy and delivery for a woman receiving omalizumab in Japan. Omalizumab may be safe to use in pregnant women with difficult-to-control asthma.