After IM oxytocin injection, uterine response occurs within 3–5 min and can last for up to 2–3 hours.8 18 19 27 Direct intramyometrial (IMY) injection of uterotonics can also promote uterine contraction.28 29 IMY oxytocin injection is believed to promote immediate uterine contraction by local effect and by drug absorption from the myometrium into the systemic circulation.28 30–32 Although oxytocin is not licensed for IMY use,18 19 this route of administration has been tested for preventing PPH at CS since 1990.28 30–32. The gene discussed is OXT; the disease is pulmonary arterial hypertension.