Pregnant women with severe pulmonary arterial hypertension (PAH) have a high maternal mortality risk. Regardless of the PAH severity, the possibility of maternal death increases before and after childbirth. In general principle, if pregnancy happens, termination is the recommendation. Several case reports noted successful deliveries of pregnant women with PAH while using the drugs of anticoagulants, calcium channel blockers, prostaglandins, and phosphodiesterase V inhibitors. However, choices of treatment are generally achieved by clinical experiences because of no established guidelines of treatments for PAH in pregnancy. We describe a case of a 31-year-old pregnant woman with mild PAH who successfully delivered a viable newborn under close observation and without any medications. In the state of no consensus of the management for PAH in pregnancy, prior to termination or empirical drug treatments, close observation without medications could be considered in mild PAH.