A 27-year-old gravida 2 para 1 woman presents to the office for a prenatal visit at 36 weeks’ gestation accompanied by her husband and their son. Her current pregnancy has been uncomplicated except for asymptomatic group B Streptococcus (GBS) bacteriuria at 11 weeks’ gestation that was successfully treated with antibiotics. She denies any fever, dysuria or urge incontinence. Her previous pregnancy was an uncomplicated vaginal delivery delivered at 39 weeks’ gestation. Her first child is RhD-negative. Past medical history is significant for asthma which is well controlled with albuterol as needed. Her husband’s blood type is AB-. Vital signs are within normal limits. Physical examination shows a uterus that is consistent with a 36-week gestation.
Which of the following is the most appropriate next step in management of this patient?
A) Administration of intrapartum penicillin G now
This patient has a previous confirmed GBS colonization that was successfully treated in this current pregnancy. GBS prophylaxis is indicated at 36 weeks’ gestation without the need for further testing.
Answer choice B: Administration of intrapartum penicillin to the newborn after delivery, is incorrect. This is only appropriate if the neonate has confirmed GBS infection or has clinical signs of infection.
Answer choice C: Administration of Rho(D) immune globulin to prevent alloimmunization, is incorrect. Antepartum prophylaxis with Rho(D) immune globulin is not indicated if the father is Rh(D) negative. Rh is inherited in an autosomal dominant pattern. If the baby is Rh+, it is from the mother who already recognizes it, so is not a risk for alloimmunization.
Rho(D) immune globulin is administered to the mother at 28-32 weeks and within 72 hours of delivery if the baby is RhD+. Other indications for prophylactic administration of Rho(D) immune globulin are spontaneous abortion, ectopic pregnancy, hydatiforme mole, threated abortion, abdominal trauma, chorionic villous sampling, amniocentesis, 2nd & 3rd semester bleeding, and external cephalic version.
Answer choice D: GBS rectovaginal swab, is incorrect. GBS rectovaginal screening cultures are performed on all pregnant people at 36+0 to 37+6 weeks of gestation, except to patients with GBS bacteriuria during the current pregnancy and patients who previously gave birth to an infant with invasive GBS disease.
Answer choice E: Indirect Coombs test, is incorrect. The indirect Coombs test is monitored montly until 24 weeks and then every two weeks in the first alloimmunized pregnancy with a RhD-positive fetus. There is no indication in the vignette that this fetus is RhD-positive, so monitoring with the indirect Coombs test is not indicated.
