The diagnosis is based on clinical presentation, quantitative HCG, ultrasound, and pathologic evaluation. A solid, heterogeneous, echogenic mass has a positive predictive value of 80%, but is present in only a minority of cases. A thickened endometrium of > 10 mm is usually considered abnormal, though no consensus exists on the appropriate cutoff. A cut-off of 8 mm or more has 34% positive rate, while a cut off of 14 mm or more has 85% sensitivity, 64% specificity for the diagnosis. Color Doppler flow in the endometrial canal can increased confidence in the diagnosis, though its absence does not exclude it, as 40% of cases of retained<unk>  have little or no flow. The differential in suspected cases includes uterine atony, blood clot, gestational trophoblastic disease, and normal post partum appearance of the uterus. Post partum blood clot is more common, reported in up to 24% of postpartum patients, and tends to be more hypoechoic than retained<unk>  with absent color flow on Doppler, and resolving spontaneously on follow up scans. The presence of gas raises the possibility of post partum endometritis, though this can also be seen in up to 21% of normal post pregnancy states. The normal post partum uterus is usually less than 2 cm in thickness, and continues to involute on follow up scans to 7 mm or less over time. Retained<unk>  are not uncommon, occurring in approximately 1% of all pregnancies, though it more common following abortions, either elective or spontaneous. There is significant overlap between appearance of a normal post partum uterus and retained<unk> . If there is no endometrial canal mass or fluid, and endometrial thickness is less than 10 mm and without increased flow, retained<unk>  are statistically unlikely. Infections Recent studies indicate that the<unk>  may be susceptible to pathogenic infections, including viral infections. Indeed, footprints of JC polyomavirus and Merkel cell polyomavirus have been detected in chorionic villi from females affected by spontaneous abortion as well as pregnant women. Another virus, BK polyomavirus has been detected in the same tissues, but with lesser extent.
Products of conception
Pregnancy specific biological substances
Reproductive technology
Artificial womb
Environmental toxicants and fetal development
Newborn transport
Maternal effect
Prenatal development