What causes a molar pregnancy?

This is a chance biological event. It is not caused by exercise, sex, stress, travel, work, or anything the pregnant person did. A molar pregnancy belongs to a group of conditions called gestational trophoblastic disease.

In a complete mole, the fertilised egg has no working maternal chromosomes and the genetic material comes from the sperm. Abnormal placental tissue develops, but an embryo does not.

In a partial mole, an egg is fertilised with an extra set of paternal chromosomes. Some fetal tissue may begin to form, but the pregnancy cannot develop normally. Both types can produce high levels of the pregnancy hormone hCG and require specialist follow-up after removal.

Diagnosis may involve ultrasound, hCG blood tests, and examination of pregnancy tissue. Treatment usually removes the abnormal tissue from the uterus. Your team then measures hCG until it reaches the expected level and follows it for the recommended period.

Use the contraception method agreed with your clinical team and wait for their advice before trying for another pregnancy, because a new pregnancy also raises hCG and can make monitoring difficult to interpret. Attend every scheduled blood or urine test even when you feel physically well.

Contact a pregnancy assessment service promptly for vaginal bleeding, severe or persistent nausea and vomiting, pelvic pressure, or pain during a suspected or confirmed pregnancy. Molar pregnancy often presents with vaginal bleeding, but bleeding also occurs for many other reasons and needs clinical assessment rather than assumptions.

Go to emergency care for heavy bleeding, fainting, severe abdominal pain, breathlessness, chest pain, or feeling acutely unwell. After treatment, tell the specialist team about renewed bleeding or symptoms between planned hCG checks.

Ask whether the findings show a complete or partial mole, how the tissue will be removed, where hCG tests will be done, and which contraception suits you during monitoring. Also ask whom to contact for urgent symptoms and when another pregnancy can be planned.