The Society for Maternal-Fetal Medicine (SMFM) Publications Committee thanks Dr Sala et al for their interest and comments on this important topic. They raise 3 issues: (1) the role of experienced operators and centers of expertise in care of patients who require invasive procedures, (2) the risks and benefits of prenatal vs postnatal therapy for fetal anemia at various gestational age ranges, and (3) lack of long-term data on fetuses that undergo fetal blood sampling.

In fact, SMFM recommends that fetal blood sampling be performed by experienced operators at centers with expertise in invasive fetal procedures when feasible (see guideline recommendation #4). With respect to the authors’ second point, this guideline did not address specifically the upper range of gestational age for fetal blood sampling or intrauterine transfusion. The decision is complex and based on the severity of the fetal condition, whether this is the first or a repeat procedure, the risks of prematurity at that given gestational age given the fetal condition, other mitigating maternal or fetal factors, and operator/center expertise. This clinical question was beyond the scope of this document and will be addressed in an upcoming SMFM Clinical Guideline- The Fetus at Risk for Anemia: Diagnosis and Management . In addition, this guideline will address the third point and summarize the available data regarding the short- and long-term outcomes for fetuses who require in utero therapy.