This is called a decidual cast. It occurs when the lining of a woman's uterus sheds as one massive solid piece of tissue during her period. : r/MakeMeSuffer

Look at the weird creature that came out of my vagina (endometrial

What Is A Decidual Cast? OB-GYNs Explain Why The Menstrual Anomaly

Decidual Cast: What Is It, Symptoms, and When to Seek Help

What is a decidual cast? See photos and learn the cause behind it

Non-Painful Out of Pill Membranous Dysmenorrhoea

Decidual Cast: What Is It, Symptoms, and When to Seek Help

Decidual Cast (TW: uterine lining) : r/endometriosis

Decidual Cast: Structure, Symptoms, Causes

meowr_11 (u/meowrii_) - Reddit

Decidual Cast: What It Looks Like, Causes, Risks

Woman Goes Viral for Detailing Rare Experience of Decidual Cast

Woman Goes Viral for Detailing Rare Experience of Decidual Cast

Decidual cast: What it is, causes, risks, and more