Is There a Placenta with Blighted Ovum?
Yes, a placenta (chorionic tissue) is present in a blighted ovum (anembryonic pregnancy), though it develops abnormally without an embryo. 1, 2
Understanding Anembryonic Pregnancy Structure
An anembryonic pregnancy—the preferred modern term over "blighted ovum"—consists of a gestational sac with surrounding trophoblastic tissue (early placental tissue) but no embryo. 3, 1 The key anatomical components include:
- Gestational sac: A fluid-filled structure measuring ≥25 mm in diameter without an embryo 3, 1
- Trophoblastic reaction: The placental precursor tissue that forms around the gestational sac, which can appear well-defined and continuous on ultrasound 4
- Chorionic tissue: This represents the early placental material that develops even in the absence of an embryo 2
Clinical and Pathological Evidence
The presence of placental/chorionic tissue in anembryonic pregnancies is confirmed through multiple lines of evidence:
- Histopathologic examination of evacuated tissue from anembryonic pregnancies reveals placental villi and chorionic tissue in approximately 50% of cases that meet ultrasound criteria for blighted ovum 5
- Hormonal production continues from the trophoblastic tissue, with variable but often normal levels of β-hCG, progesterone, and estradiol, demonstrating functional placental tissue despite embryonic absence 5
- Ultrasound findings show a trophoblastic reaction surrounding the gestational sac, which represents developing placental tissue 4
Important Clinical Distinctions
When managing anembryonic pregnancies, recognize these critical points:
- Differentiation from complete molar pregnancy: Early complete moles (before 12 weeks) can sometimes mimic anembryonic pregnancy, but molar pregnancies show characteristic hyperechoic areas with multiple cystic spaces rather than a simple empty sac 3, 6
- Retained products of conception: Following spontaneous or induced passage of an anembryonic pregnancy, residual chorionic/placental tissue may remain, appearing as intracavitary vascularized tissue on Doppler ultrasound 3
- Genetic implications: Anembryonic pregnancies frequently result from chromosomal errors (50-60% of cases), the same mechanism underlying other early pregnancy losses, and recurrent anembryonic pregnancies may indicate specific genetic mutations (NLRP7, KHDC3L genes) 7
Management Implications
The presence of placental tissue in anembryonic pregnancy has direct clinical relevance:
- Histopathologic confirmation is recommended after evacuation to confirm intrauterine pregnancy and rule out gestational trophoblastic disease 1
- Rh immunoprophylaxis is required for all Rh-negative women (50 μg anti-D immunoglobulin) because fetomaternal hemorrhage occurs in 32% of spontaneous abortions, even without an embryo present 2
- Active management (medical or surgical) is preferred over expectant management due to risks of infection, hemorrhage, and coagulopathy from retained chorionic tissue 1, 2