A 32-year-old woman has had three pregnancies, all ending in stillbirths in the first trimester. On physical examination, she and her only spouse for all pregnancies have no abnormalities. Which of the following laboratory tests is most appropriate to perform on this woman for elucidating potential causes for recurrent fetal loss?

Recurrent fetal loss suggests a parental cause. A chromosomal abnormality such as a Robertsonian translocation may account for stillbirths, particularly in the first trimester, when many fetal losses result from chromosomal abnormalities. A genome-wide associations study applies to populations, not individuals, and establishes linkages of common diseases such as hypertension and diabetes mellitus to polygenic risks. Fluorescence in situ hybridization (FISH) analysis is useful for establishing chromosome number and morphology, such as translocations, inversions, and deletions, but is not as definitive as a karyotype. PCR analysis is useful for identifying specific gene defects, not whole chromosomal abnormalities. Tandem mass spectroscopy is used in newborn screening for biochemical inborn errors of metabolism, such as phenylketonuria.