C-Section Raises Placental Cancer Risk by 45%

What is gestational trophoblastic neoplasia and how common is it in Brazil?

Gestational trophoblastic neoplasia (GTN) is a rare cancer that develops from placental cells and grows inside the uterus. It is the most serious complication of a molar pregnancy — an abnormal fertilisation that produces an abnormal placental structure, sometimes without a foetus (complete mole) or with a non-viable foetus (partial mole). In Brazil, molar pregnancy affects roughly 1 in every 200–400 pregnancies, with about 2,900 new GTN cases recorded every year.

What did the new Brazilian study find?

Researchers at the Maternidade Escola of the Universidade Federal do Rio de Janeiro (UFRJ) found that people who had previously undergone a caesarean section have a 45% higher risk of developing GTN after a molar pregnancy. The study analysed data from 2,904 patients treated at UFRJ and the New England Trophoblastic Disease Center (affiliated with Harvard University) between 2002 and 2022.

Among women with a prior caesarean, 26.5% developed the cancer, compared with 20.8% of those without that history. Researchers controlled for all other known risk factors, confirming that a previous caesarean independently raises the risk.

Who led the research and why Brazil?

The study was led by Dr Gabriela Paiva, an obstetrician at the UFRJ clinic. The idea emerged after a similar but smaller Korean study was published. Brazil was the ideal setting: the UFRJ clinic is the third-largest molar pregnancy treatment and research centre in the world, attending roughly 80 patients every week. Brazil also has one of the world's highest caesarean rates, making the sample uniquely large and precise.

What risk factors were already known?

Before this study, higher GTN risk was already linked to: complete molar pregnancy (vs partial), age over 40, very high HCG hormone levels, previous complete mole, and ovarian cysts. The caesarean history now adds to this list as an independent factor.