There is marked maceration, hydrops, and a large hygroma occupying the posterior neck region. The most likely chromosomal abnormality to produce these findings in a female fetus is monosomy X, or Turner syndrome, with a karyotype of 45, X. (The second choice is Down syndrome, with karyotype of 47, XX, +21). Turner syndrome is one of the more common causes for early (first trimester) fetal loss, though stillbirths with monosomy X may also occur in the second and third trimesters. Livebirths with monosomy X are uncommon, and may represent some degree of mosaicism. If survival does occur, the hygroma, which results from abnormal lymphatic development, resolves into the characteristic web neck. Such persons are short and may have other anomalies including: renal anomalies such as horseshoe kidney and urinary tract duplications, cardiovascular anomalies including aortic coarctation, atrial septal defect, and patent ductus, skeletal anomalies including short 4th metacarpal and cubitus valgus, and infertility from hypoplastic genitalia including "streak" ovaries.