Retained products of conception

Retained products of conception (RPOC) refer to the persistence of placental and/or fetal tissue in the uterus following delivery, termination of pregnancy or a miscarriage. 

Epidemiology

RPOC complicate ~1-5% of all routine vaginal deliveries ¹².

According to one prospective study, RPOC was present in after a third-trimester delivery in around 2.7% of women, whereas it was diagnosed in pregnancies ending during the second and first trimesters in 40% and 17%, respectively ¹². 

It occurs with greater frequency with:

• medical termination of pregnancy (MTP) 
• second-trimester miscarriage
• placenta accreta

Clinical presentation

Common symptoms include vaginal bleeding and abdominal or pelvic pain, similar to patients with gestational trophoblastic disease. Some patients may have fever ¹¹.

Differentiation of these entities is important because retained products of conception are treated conservatively or with curettage, while gestational trophoblastic disease may require chemotherapy.

ß-human chorionic gonadotropin (beta-hCG) remains elevated in patients with gestational trophoblastic disease but falls to an undetectable level over 2-3 weeks, in cases of retained products.

Radiographic features

Ultrasound

Ultrasound is typically the first-line investigation in suspected retained products of conception:

• a variable amount of echogenic or heterogeneous material within the endometrial cavity 
• in some instances, this may present like an endometrial or intrauterine mass
• presence of vascularity within the echogenic material supports the diagnosis but the absence of colour Doppler flow has a low negative predictive value because retained products of conception may be avascular ⁹
• calcification may be present

Retained products of conception can be suspected on ultrasound if the endometrial thickness is >10 mm following dilatation and curettage or spontaneous abortion (80% sensitive).

MRI

MRI appearance is variable, and consists of soft tissue within the endometrial cavity, which may be variably enhancing. There may be variable degree of associated myometrial thinning and obliteration of the junctional zone.

Signal characteristics include ¹:

• T1: variable heterogeneous signal
• T2: variable heterogeneous signal
• T1 C+ (Gd): variable enhancement

Differential diagnosis

For ultrasound appearances consider:

• normal postpartum appearance
• blood clot within the endometrial cavity (often co-exists): non-vascular on colour Doppler ultrasound
• endometritis
• gestational trophoblastic disease
• uterine arteriovenous malformation (if prominent blood flow is present)

See also

• incomplete miscarriage