A. Frequency and duration of contractions: Heavy bleeding without contractions is not typically caused by labor. This option is irrelevant to the client’s current condition. B. Fetal lung maturity: While fetal lung maturity is essential, it is unrelated to the client's heavy vaginal bleeding. C. Rh incompatibility: This condition does not present with sudden, heavy vaginal bleeding in the third trimester. D. Location of the placenta: Heavy, painless vaginal bleeding in late pregnancy can indicate placenta previa. Ultrasound is essential to assess placental location to rule out this potentially life-threatening condition.