A woman at 31 weeks' gestation complains of feeling dizzy and lightheaded when she lies on her back. She is Rh negative but denies vaginal bleeding, abdominal trauma, or abdominal pain. The diagnosis is probably the supine hypotensive syndrome.
In which of the following circumstances is the administration of anti-D immune globulin not necessary?
- threatened abortion and first-trimester bleeding
- genetic amniocentesis at 16 weeks' gestation
- at 28 weeks
- at 40 weeks with the onset of labor
- after delivery of an Rh-positive fetus
Answer(s): D
Explanation:
Anti-D immune globulin should be given at the time of any vaginal bleeding, trauma, or invasive procedure (e.g., amniocentesis) during pregnancy. Although maternal isoimmunization usually occurs as a result of fetomaternal transfusion at the time of delivery, a small percentage of women become isoimmunized during pregnancy. Anti-D immune globulin is routinely given to unsensitized Rh- negative women at 28 weeks' gestation to reduce this risk. Anti-D immune globulin must also be administered within 72 hours after the birth of an Rh-positive infant. Administration at 40 weeks' gestation before the onset of labor is unnecessary if the infant is Rh negative and may be ineffective if the infant is Rh positive and there is a significant fetomaternal transfusion.