# In-utero and newborn factors and thyroid cancer incidence in adult women in the Sister Study cohort

## TL;DR

This study found that certain in-utero and newborn factors, like maternal diabetes and higher birth weight, may increase the risk of thyroid cancer in adult women.

## Contribution

The study provides new evidence that maternal metabolic conditions during pregnancy may influence thyroid cancer risk in offspring.

## Key findings

- Higher DTC incidence was associated with maternal diabetes and gestational hypertension.
- Higher birth weight was linked to increased DTC risk.
- Early births were associated with lower DTC incidence.

## Abstract

Thyroid cancer is diagnosed at relatively young ages compared to other adult cancers, for reasons that remain unclear. Our study aimed to investigate associations of in-utero and newborn characteristics with differentiated thyroid cancer (DTC) incidence in adult women.

From the U.S. nationwide Sister Study cohort, we included 47,913 cancer-free women at baseline (2003–2009). We assessed associations of participants’ in-utero and newborn characteristics and DTC during follow-up using Cox regression models adjusted for attained age (timescale) and race/ethnicity.

During follow-up (median = 13.1 years), 239 incident DTC cases were identified. Higher DTC incidence was associated with maternal pre-pregnancy or gestational diabetes (hazard ratio [HR] = 2.36, 95%CI = 0.97–5.74, 5 affected cases), gestational hypertension or hypertension-related disorders (HR = 1.99, 95%CI = 1.20–3.32, 16 affected cases), and higher birth weight (HR per kg=1.24, 95%CI = 0.95–1.60). Births occurring at least two weeks before the due date were associated with lower DTC incidence (HR = 0.47, 95%CI = 0.23–0.97, 8 affected cases). In a model simultaneously adjusted for all these factors, all exposures remained associated with DTC incidence. We observed no associations for other in-utero and newborn characteristics.

These findings contribute to a growing body of evidence that in-utero exposures related to maternal metabolic abnormalities may influence thyroid cancer risk later in life.