Prevalence of preterm, low birthweight, and small for gestational age delivery after breast cancer diagnosis: a population-based study

Kristin Zeneé Black, Hazel B. Nichols, Eugenia Eng, Diane Louise Rowley

Black-white disparities in breast cancer incidence rates and birth outcomes raise concerns about potential disparities in the reproductive health of premenopausal breast cancer survivors. We examined the prevalence of preterm birth (PTB), low birthweight (LBW), and small for gestational age (SGA) by breast cancer history and effect modification by race. We analyzed linked North Carolina birth records and Central Cancer Registry files from 1990 to 2009 (n = 2,325,229). We used multivariable negative log-binomial regression to calculate prevalence ratios (PRs) and 95% confidence intervals (CIs) for the association between breast cancer history and PTB, LBW, and SGA. Of 1,912,269 eligible births, 512 births were to mothers with a previous breast cancer diagnosis history. Average age at breast cancer diagnosis was 31.8 years (SD = 4.7). Mean time from diagnosis to delivery was 3.3 years (SD = 2.8). After multivariable adjustment, the PR was 1.67 (95% CI, 1.42-1.97) for PTB, 1.50 (95% CI, 1.23-1.84) for LBW, and 1.30 (95% CI, 1.05-1.61) for SGA comparing women with a breast cancer history to the general population. Among black mothers, the PRs associated with breast cancer history for PTB, LBW, and SGA were 1.31 (95% CI, 1.00-1.72), 1.49 (95% CI, 1.14-1.94), and 1.44 (95% CI, 1.11-1.87), respectively. The corresponding PRs among white mothers were 2.06 (95% CI, 1.67-2.54), 1.53 (95% CI, 1.12-2.08), and 1.10 (95% CI, 0.77-1.58), respectively. The interaction between breast cancer history and race was statistically significant for associations with PTB, but not for LBW or SGA. In our data, women with a breast cancer history were at higher risk of delivering a PTB, LBW, or SGA infant, especially if they received chemotherapy or gave birth within 2 years of their breast cancer diagnosis date.