Is it obligatory for a woman to perform ghusl (ritual bathing) from janabah (major ritual impurity) if her husband ejaculates between her buttocks without penetration of the front or back passage, due to circumstances of pregnancy and a doctor's recommendation?

A woman is not required to perform ghusl (ritual bath) unless the glans (of the penis) or its equivalent disappears into either of her two private parts, or she discharges semen, based on the Prophet's (PBUH) saying: "When the two circumcised parts meet, ghusl becomes obligatory."