Inherited factors contribute to an inverse association between preeclampsia and breast cancer

Causal effects of hypertensive disorders of pregnancy on future gynecologic tumors: A two-sample Mendelian randomization study

BACKGROUND

Numerous observational studies have investigated the potential link between hypertensive disorders of pregnancy (HDPs) and the subsequent risks of gynecologic tumors, yet the findings have been inconsistent. In this study, we utilized Mendelian randomization (MR) approach to assess the influence of HDPs on the future risks of ovarian, cervical, endometrial, and breast cancer and uterine fibroids, controlling for confounding factors.

METHODS

The genome-wide association studies (GWAS) summary data relevant to HDPs was obtained from the FinnGen databases (10,736 cases and 136,325 controls). Gynecologic tumor outcomes were extracted from the IEU Open GWAS project and UK Biobank (47,690 cases and 1, 092,073 controls). The inverse variance weighted (IVW) approach was selected as the principal method for MR analysis, supplemented by MR-Egger, weighted median, weighted model, simple model methods, MR pleiotropy residual sum and outlier (MR-PRESSO) test, and leave-one-out method. Multivariate MR (MVMR) analysis was conducted after adjusting systolic blood pressure (SBP), body mass index (BMI) and type 2 diabetes mellitus (T2DM).

RESULTS

Our univariate MR analysis (UVMR) results revealed no significant relationship between HDPs and the risks of ovarian cancer (odds ratio [OR] = 0.924, p = 0.360), cervical cancer (OR = 1.230, p = 0.738), endometrial cancer (OR = 1.006, p = 0.949), uterine fibroids (OR = 1.155, p = 0.158), and breast cancer (OR = 0.792, p = 0.241) by IVW test. Similar results were observed in gestational hypertension and preeclampsia/eclampsia. Additionally, our study detected neither heterogeneity nor pleiotropy. MVMR analysis also provided no evidence of a causal association between HDPs and common gynecologic tumors after adjusting SBP, BMI, and T2DM.

CONCLUSION

We discovered no causal relationship between HDPs and ovarian, cervical, endometrial, breast cancer, and uterine fibroids in European populations. However, present analysis did not explore the effect of HDPs on the subtypes of gynecologic tumors across varied ethnic populations, which may require additional research.

Pre-pregnancy body mass index combined with peripheral blood PLGF, DCN, LDH, and UA in a risk prediction model for pre-eclampsia

Objective

This study analyzes the levels of peripheral blood placental growth factor (PLGF), body mass index (BMI), decorin (DCN), lactate dehydrogenase (LDH), uric acid (UA), and clinical indicators of patients with preeclampsia (PE), and establishes a predictive risk model of PE, which can provide a reference for early and effective prediction of PE.

Methods

81 cases of pregnant women with PE who had regular prenatal checkups and delivered in Jinshan Branch of Shanghai Sixth People's Hospital from June 2020 to December 2022 were analyzed, and 92 pregnant women with normal pregnancies who had their antenatal checkups and delivered at the hospital during the same period were selected as the control group. Clinical data and peripheral blood levels of PLGF, DCN, LDH, and UA were recorded, and the two groups were subjected to univariate screening and multifactorial logistic regression analysis. Based on the screening results, the diagnostic efficacy of PE was evaluated using the receiver operating characteristic (ROC) curve. Risk prediction nomogram model was constructed using R language. The Bootstrap method (self-sampling method) was used to validate and produce calibration plots; the decision curve analysis (DCA) was used to assess the clinical benefit rate of the model.

Results

There were statistically significant differences in age, pre-pregnancy BMI, gestational weight gain, history of PE or family history, family history of hypertension, gestational diabetes mellitus, and history of renal disease between the two groups (P < 0.05). The results of multifactorial binary logistic stepwise regression revealed that peripheral blood levels of PLGF, DCN, LDH, UA, and pre-pregnancy BMI were independent influences on the occurrence of PE (P < 0.05). The area under the curve of PLGF, DCN, LDH, UA levels and pre-pregnancy BMI in the detection of PE was 0.952, with a sensitivity of 0.901 and a specificity of 0.913, which is better than a single clinical diagnostic indicator. The results of multifactor analysis were constructed as a nomogram model, and the mean absolute error of the calibration curve of the modeling set was 0.023, suggesting that the predictive probability of the model was generally compatible with the actual value. DCA showed the predictive model had a high net benefit in the range of 5% to 85%, suggesting that the model has clinical utility value.

Conclusion

The occurrence of PE is related to the peripheral blood levels of PLGF, DCN, LDH, UA and pre-pregnancy BMI, and the combination of these indexes has a better clinical diagnostic value than a single index. The nomogram model constructed by using the above indicators can be used for the prediction of PE and has high predictive efficacy.

Women with preeclampsia may have reduced risk of breast cancer: a meta-analysis of cohort studies with 7.8 million participants

This review pooled data from the literature to examine the association between preeclampsia (PE) and subsequent risk of breast cancer in women. Cohort studies published in the databases of PubMed, Embase, Scopus, and Web of Science up to 18 July 2023 were searched. Adjusted data were pooled to obtain the risk ratio (RR). Eleven studies with 15 cohorts and a cumulative sample size of 7,838,693 women were included. Meta-analysis of all studies demonstrated a reduced risk of breast cancer in women with PE as compared to those without PE (RR: 0.89 95% CI: 0.83, 0.95 p < 0.001 I2 = 50%). Follow-up ranged from 8 to 29.2 years. Results did not change during sensitivity analysis. Outcomes varied on subgroup analysis based on location, study type, data extraction method, incidence of breast cancer, and follow-up. To conclude, women with PE may have a reduced risk of breast cancer later in life. However, the risk reduction is minimal and may not have much clinical significance. The evidence is also limited by high inter-study heterogeneity and lack of adjustment of all possible confounders.

The levels of peripheral blood TNF-α, Decorin and neutrophils MAPK1 mRNA levels of patients with preeclampsia and their clinical significance

Objective: This study analyzed the levels of peripheral blood tumor necrosis factor-α (TNF-α), Decorin (DCN) and Mitogen-activated protein kinase 1 (MAPK1) mRNA in neutrophils of patients with preeclampsia and their correlations, in order to provide more thoughts on the diagnosis and treatment of clinical patients. Methods: 81 patients with preeclampsia who had regular prenatal checkups and delivered in our hospital from June 2020 to April 2022 were analyzed, including 26 patients with early-onset and 55 patients with late-onset, and 50 pregnant women with normal pregnancy who had prenatal checkups and delivered in our hospital during the same period were selected as the control group. Record the clinical data of patients, record the expression of peripheral blood TNF-α, DCN and neutrophils MAPK1 mRNA of patients with early-onset, late-onset and the control group, and record the correlation between DCN level, MAPK1 mRNA expression and TNF-α level of patients with preeclampsia. Results: The diastolic and systolic blood pressures were significantly higher in early-onset and late-onset patients, and the gestational week of delivery was significantly lower in early-onset and late-onset patients, respectively (p < .05); there was no statistically significant difference in the average age, BMI, average pregnancy time, and average births between the three groups (p > .05). The expressions of peripheral blood TNF-α, DCN, and neutrophils MAPK1 mRNA of the early-onset and late-onset groups were all higher than those in the control group (p < .05); and the expressions of TNF-α, DCN, and MAPK1 mRNA in the peripheral blood of the early-onset group were all higher than those in the late-onset group (p < .05); Pearson correlation analysis showed that DCN level and TNF-α level in patients with preeclampsia were positively correlated (r = 0.98639, p < .05); Neutrophils MAPK1 mRNA expression and TNF-α level were positively correlated (r = 0.9611, p < .05). Conclusion: TNF-α, DCN and neutrophils MAPK1 mRNA were all highly expressed in the peripheral blood of patients with pre-eclampsia and were more significantly elevated in patients with early-onset preeclampsia, and the expression levels of DCN and MAPK1 mRNA were positively correlated with TNF-α levels. It is possible that all three factors are involved in the pathogenesis of preeclampsia, and are expected to be used as indicators for early prediction and diagnosis.

Gestational Hypertensive Disorders and Maternal Breast Cancer Risk in a Nationwide Cohort of 40,720 Parous Women

BACKGROUND

Preeclampsia and gestational hypertension are hypothesized to be associated with reduced maternal breast cancer risk, but the epidemiologic evidence is inconclusive. Our objective was to examine associations between gestational hypertensive disorders and breast cancer in a nationwide cohort of women with a family history of breast cancer.

METHODS

Women ages 35-74 years who had a sister previously diagnosed with breast cancer, but had never had breast cancer themselves, were enrolled in the Sister Study from 2003 to 2009 (N = 50,884). At enrollment, participants reported diagnoses of eclampsia, preeclampsia, or gestational hypertension in each pregnancy. We used Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between history of a gestational hypertensive disorder and incident invasive breast cancer or ductal carcinoma in situ among 40,720 parous women. We used age as the time scale and adjusted for birth cohort, race-ethnicity, and reproductive, socioeconomic, and behavioral factors. We examined effect measure modification by risk factors for gestational hypertensive disease and breast cancer and assessed possible etiologic heterogeneity across tumor characteristics.

RESULTS

The prevalence of gestational hypertensive disease was 12%. During follow-up (mean = 10.9 years), 3,198 eligible women self-reported a breast cancer diagnosis. History of a gestational hypertensive disorder was not associated with breast cancer risk (HR = 1.0; 95% CI = 0.90, 1.1). We did not observe clear evidence of effect measure modification or etiologic heterogeneity.

CONCLUSIONS

History of a gestational hypertensive disorder was not associated with breast cancer risk in a cohort of women with a first-degree family history of breast cancer.

Hypertensive diseases of pregnancy and risk of breast cancer in the Black Women's Health Study

PURPOSE

Compared to white women, Black women have increased risk of developing hypertensive diseases of pregnancy (HDOP) and have a higher incidence of aggressive breast cancer subtypes. Few studies of HDOP and breast cancer risk have included large numbers of Black women. This study examined the relation of HDOP to incidence of breast cancer overall and by estrogen receptor (ER) status in Black women.

METHODS

We followed 42,982 parous women in the Black Women's Health Study, a nationwide prospective study of Black women. Multivariable Cox proportional hazards regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) to assess associations of self-reported HDOP, including preeclampsia and gestational hypertension, with breast cancer incidence overall and by ER subtype, adjusted for age and established breast cancer risk factors.

RESULTS

Over 20 years of follow-up, we identified 2376 incident breast cancer cases. History of HDOP (11.7%) was not associated with breast cancer risk overall (HR 0.98; 95% CI 0.87, 1.11). HRs for invasive ER+ and ER- breast cancer were 1.11 (95% CI 0.93, 1.34) and 0.81 (95% CI 0.61, 1.07), respectively.

CONCLUSIONS

HDOP was not associated with risk of overall breast cancer in Black women. A suggestive inverse association with ER- breast cancer may reflect an anti-tumorigenic hormone profile in HDOP, but those results require confirmation in other studies.

Preeclampsia and cancer risk in women in later life: a systematic review and meta-analysis of cohort studies

IMPORTANCE

Results of this work may provide some guidance for subsequent ovarian cancer screening in women with preeclampsia and provide new directions for future studies.

OBJECTIVE

This study investigated the difference in cancer risk between women with preeclampsia and women with a normal pregnancy.

EVIDENCE REVIEW

Electronic databases, namely PubMed, Embase, and the Cochrane Library, were searched for relevant studies from database inception to February 4, 2021. The results are expressed as risk ratios (RRs).

FINDINGS

The study included 13 cohort studies comprising 5,254,150 participants. The difference in the total cancer risk between the control and preeclampsia groups was statistically nonsignificant. However, breast cancer (BC) risk was lower in the preeclampsia group (RR = 0.88, 95% confidence interval (CI) = 0.83-0.93; I2 = 57.2%). A subgroup analysis stratified by reproductive factors demonstrated that BC risk in the preeclampsia population decreased in parous women (RR = 0.79, 95% CI = 0.72-0.87; I2 = 0%), women with full-term pregnancies (RR = 0.79, 95% CI = 0.75-0.84; I2 = 0%), and women with increasing parity. Furthermore, BC risk reduced in women with preeclampsia regardless of their menopausal status and the sex of their offspring.

CONCLUSIONS AND RELEVANCE

Overall, women with preeclampsia have a decreased BC risk and increased ovarian cancer risk compared with the normal population. A subgroup analysis stratified by reproductive factors demonstrated that BC risk decreased in the preeclampsia population in parous women, women with full-term pregnancies, and women with increasing parity regardless of their menopausal status and the sex of their offspring.

Assessment of All-Cause Cancer Incidence Among Individuals With Preeclampsia or Eclampsia During First Pregnancy

IMPORTANCE

Preeclampsia or eclampsia (preeclampsia/eclampsia) during pregnancy induces major physiological changes and may be associated with specific cancer occurrences in later life. The current data regarding the association between preeclampsia/eclampsia and cancer are heterogeneous, and cancer risk after preeclampsia/eclampsia could be different depending on the organ. These uncertainties warrant reexamination of the association between preeclampsia/eclampsia and the risk of cancer overall and by specific cancer type.

OBJECTIVE

To evaluate the risk of cancer, overall and by type, after preeclampsia/eclampsia during a first pregnancy.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study used data from the French hospital discharge database to identify all female individuals who had a pregnancy-associated hospitalization between January 1, 2010, and December 31, 2019. To allow a minimum of 2 years for the detection of medical history, individuals with a first detected pregnancy before January 1, 2012, were excluded, as were those with a cancer-associated hospitalization before or during their first detected pregnancy. Exposures, comorbidities, and occurrences of cancer were evaluated using data from the medico-administrative registers of hospitalizations in private and public French hospitals. Cox proportional hazards models were used to analyze cancer risk according to the occurrence of preeclampsia/eclampsia during first pregnancy.

EXPOSURES

Preeclampsia/eclampsia-associated hospitalization during the first detected pregnancy.

MAIN OUTCOMES AND MEASURES

The primary outcome was the incidence of cancer, including myelodysplastic or myeloproliferative diseases, after a first pregnancy with and without preeclampsia/eclampsia.

RESULTS

After exclusions, a total of 4 322 970 female individuals (mean [SD] age at first detected pregnancy, 29.6 [6.2] years) with and without preeclampsia/eclampsia during their first pregnancy were included. Of those, 45 523 individuals (1.1%) were diagnosed with preeclampsia/eclampsia during their first detected pregnancy. The maximum follow-up was 8 years, during which 29 173 individuals (0.7%) were diagnosed with cancer. No significant difference in overall cancer incidence was found between those with and without preeclampsia/eclampsia during their first pregnancy (adjusted hazard ratio [AHR], 0.94; 95% CI, 0.84-1.05). Preeclampsia/eclampsia was associated with an increase in the risk of myelodysplastic syndromes or myeloproliferative diseases (AHR, 2.43; 95% CI, 1.46-4.06) and kidney cancer (AHR, 2.19; 95% CI, 1.09-4.42) and a decrease in the risk of breast cancer (AHR, 0.79; 95% CI, 0.62-0.99) and cervical cancer (AHR, 0.75; 95% CI, 0.58-0.96).

CONCLUSIONS AND RELEVANCE

In this study, a history of preeclampsia/eclampsia during first pregnancy was associated with an increase in the incidence of myelodysplastic or myeloproliferative diseases and kidney cancer and a decrease in the incidence of cervical and breast cancers. These associations might reflect an underlying common factor among preeclampsia/eclampsia and these pathologies and/or an association between preeclampsia/eclampsia and the development of these cancers.

Long intergenic ncRNA 00473 improves the invasion of trophoblastic cells via miR-16-5p

Preeclampsia (PE) is a common disease among pregnant women and is characterized by high blood pressure, edemas, proteinuria, etc. However, the underlying mechanism of PE is still not clear. Our results may provide a new understanding of the pathogenesis of PE and a therapeutical target for the treatment of the disease. Levels of long intergenic ncRNA 00473 (LINC00473), miR-16-5p, MMP2, MMP9, Bcl-2, Bax, and C caspase-3 in placental tissues or human trophoblastic cells were assessed. HTR8/SVneo and JEG-3 cells were transfected with LINC00473, miR-16-5p mimic, LINC00473 siRNA, or miR-16-5p inhibitor alone, or co-transfected with LINC00473 and miR-16-5p mimic or LINC00473 siRNA and miR-16-5p inhibitor. Viability, apoptosis, migration and invasion of cells were assessed by Cell Counting Kit-8, flow cytometry, wound healing assay and Transwell assay, respectively. The target gene of LINC00473 was analyzed using Starbase and dual-luciferase reporter assay. LINC00473 level was down-regulated in placental tissues of PE patients. LINC00473 overexpression increased cell viability, migration, invasion, and MMP2, MMP9 and Bcl-2 levels, yet decreased the apoptosis rates and Bax and C caspase-3 levels in cells; however, LINC00473 silencing had the opposite effect. LINC00473 targeted miR-16-5p and miR-16-5p level was negatively related to LINC00473 level. MiR-16-5p mimic reversed the promoting effect of LINC00473 overexpression on the invasion of HTR8/SVneo and JEG-3 cells, while miR-16-5p inhibitor reversed the inhibitory effect of LINC00473 silencing on the invasion of these cells. In conclusion, LINC00473 improved the invasion of human trophoblastic cells via miR-16-5p.

Cancer and Cardiovascular Risk in Women With Hypertensive Disorders of Pregnancy Carrying a Common IGF1R Variant

OBJECTIVE

To evaluate the impact of insulin-like growth factor 1 receptor variant rs2016347 on the risk for breast and nonbreast cancers and cardiovascular disease in women with a history of hypertensive disorders of pregnancy (HDP).

PATIENTS AND METHODS

This retrospective cohort study included all parous women in the UK Biobank with prior rs2016347 genotyping (N=204,155), with enrollment taking place from March 2006 to July 2010. History of HDP was self-reported, and outcomes included breast and all nonbreast cancers, hospital diagnoses of hypertension and cardiovascular disease, and direct blood pressure measurements.

RESULTS

Women with previous HDP had a higher risk for future hypertension and cardiovascular diagnoses, increased blood pressures, and lower risk for breast cancer compared with women without HDP, consistent with prior studies. Hazard ratios for all nonbreast cancers were unchanged. However, when taking genotype into account, HDP-positive women carrying at least 1 thymine (T) allele of rs2016347 had a lower risk for nonbreast cancer (hazard ratio, 0.59; 95% CI, 0.37 to 0.92; P=.02) and lower systolic blood pressure (-2.08±0.98 mm Hg; P=.03) compared with women with the guanine/guanine (GG) genotype with positive evidence of interaction (HDP:T allele) for both outcomes; P=.04 and P=.03, respectively.

CONCLUSION

Women who experience HDP and carry a T allele of rs2016347 have 41% lower risk for developing nonbreast cancer and a lower systolic blood pressure of 2.08 mm Hg when compared with those with the GG genotype, suggesting a possible role of the insulin-like growth factor 1 axis for both cardiovascular and cancer risk in women with HDP.

Hypertensive Disorders of Pregnancy (HDP) and the Risk of Common Cancers in Women: Evidence from the European Prospective Investigation into Cancer (EPIC)-Norfolk Prospective Population-Based Study

Simple Summary

One in ten pregnancies is complicated with high blood pressure. Whilst the association between high blood pressure during pregnancy and cardiovascular disease in later life is well-established, its association with cancer is less so. We aimed to determine the association between hypertensive disorders of pregnancy (HDP) and common cancers in a UK population-based longitudinal study. No statistically significant association was found between HDP and the odds of future cancer, and independent site-specific cancers of breast, colorectal, lung, ovarian and endometrial cancers in a UK-based general practice-derived population. Current research underlining HDP and cancer risk is limited to specific populations only. Future work in different populations is required, focusing on complex genetic and hormonal factors involved in these conditions.

Abstract

Purpose: The purpose was to determine the association between HDP and cancer in a UK cohort. Methods: Between 1993 and 1997, participants from the EPIC-Norfolk cohort attended baseline health-checks and completed questionnaires, where a history of HDP was collected. Incident cancer cases were identified through NHS record linkage until March 2016. Univariable and multivariable logistic regression analyses were employed to determine the association between HDP and odds of cancer, with adjustment for potential confounders including co-morbidities, sociodemographic, lifestyle and reproductive factors. Results: 13,562 women were included after excluding prevalent cancer cases and women with no pregnancies. 2919 (21.5%) reported HDP and 2615 incident cancers occurred during mean follow up of 19 years. Median age (IQR) at baseline for incident cancer was 60.8 (±14.8) years. Among incident cancer cases, 578 (22.1%) had HDP. In multivariable analyses, HDP had odds ratio (OR) 1.06; 95% CI 0.95–1.18 for incident cancer. The ORs (95% CIs) for common site-specific cancers including breast, colorectal, lung, ovarian and endometrial cancers were 1.06 (0.88–1.28), 1.15 (0.92–1.45), 0.96 (0.68–1.35), 1.30 (0.93–1.83) and 1.16 (0.80–1.67). Conclusion: We found no association between HDP and cancer risk. Further studies are required to confirm and account for any underlying genetic factors involved in pregnancy-related exposures and cancer risk.

Mother's age at delivery and daughters' risk of preeclampsia

BACKGROUND

Some cardiovascular disease risk factors are associated with both risk of preeclampsia and having been born to a younger or older mother. We examined whether mother's age at delivery predicts a primiparous daughter's risk of preeclampsia.

METHODS

The analysis included 39 803 Sister Study participants (designated as "daughters") born between 1930 and 1974. Using log-binomial regression, we estimated relative risks (RR) of preeclampsia in the first pregnancy ending in birth ("primiparous preeclampsia") associated with mother's age at the daughter's birth. Models included: number of older full and maternal half-siblings, income level growing up, daughter's age at delivery, race/ethnicity, and 5-year birth cohort. We examined self-reported relative weight at age 10 (heavier than peers versus not) as a potential effect measure modifier.

RESULTS

Overall, 6.2% of daughters reported preeclampsia. Compared with those who had been born to 20-24-year old mothers, daughters of teenage mothers had a relative risk of 1.20 (95% confidence interval (CI) 1.01, 1.43) and daughters of mothers ≥25 had a ~10% lower risk. Relative weight at age 10 modified the association, with an inverse association between mother's age at delivery and preeclampsia seen only among daughters with low/normal childhood relative weight. In this subset, results were consistent across strata of daughter's age at menarche and age at first birth.

CONCLUSIONS

These findings, based on self-reported data, require replication. Nevertheless, as women increasingly delay childbearing, they provide some reassurance that having been born to an older mother is not, per se, a risk factor for primiparous preeclampsia.

Long Noncoding RNA 00473 Is Involved in Preeclampsia by LSD1 Binding-Regulated TFPI2 Transcription in Trophoblast Cells

Preeclampsia (PE) is a syndrome manifested by high blood pressure that could develop in the latter half of pregnancy; however, the underlying mechanisms are not understood. Recent evidence points to the function of noncoding RNAs (ncRNAs) as novel regulators of the invasion, migration, proliferation, and apoptosis of trophoblasts involved in the development of placental vasculature. Here, we investigated the role of long intergenic ncRNA 00473 (linc00473) in PE and the associated molecular mechanisms. The expression of linc00473 was downregulated in the placenta of patients with severe PE as revealed by qRT-PCR analysis. In vitro, linc00473 knockdown in trophoblast cell lines HTR-8/SVneo, JAR, and JEG3 significantly inhibited cell proliferation and promoted apoptosis, whereas linc00473 overexpression stimulated trophoblast proliferation. The mechanistic insights were provided by RNA-seq and qRT-PCR, which revealed that linc00473 could regulate the transcription of genes relevant to cell growth, migration, and apoptosis. In particular, linc00473 inhibited the expression of tissue factor pathway inhibitor 2 (TFPI2) through binding to lysine-specific demethylase 1 (LSD1). These results indicate that linc00473 could be involved in the pathogenesis and development of PE and may be a candidate biomarker as well as therapeutic target for this disease.

Breast cancer risk in relation to history of preeclampsia and hyperemesis gravidarum: Prospective analysis in the Generations Study

Preeclampsia and hyperemesis gravidarum are pregnancy complications associated with altered sex hormone levels. Previous studies suggest preeclampsia may be associated with a decreased risk of subsequent breast cancer and hyperemesis with an increased risk, but the evidence remains unclear. We used data from the Generations Study, a large prospective study of women in the United Kingdom, to estimate relative risks of breast cancer in relation to a history of preeclampsia and hyperemesis using Cox regression adjusting for known breast cancer risk factors. During 7.5 years average follow‐up of 82,053 parous women, 1,969 were diagnosed with invasive or in situ breast cancer. Women who had experienced preeclampsia during pregnancy had a significantly decreased risk of premenopausal breast cancer (hazard ratio (HR) =0.67, 95% confidence interval (CI): 0.49–0.90) and of HER2‐enriched tumours (HR = 0.33, 95% CI: 0.12–0.91), but there was no association with overall (HR = 0.90, 95% CI: 0.80–1.02) or postmenopausal (HR = 0.97, 95% CI: 0.85–1.12) breast cancer risk. Risk reductions among premenopausal women were strongest within 20 years since the last pregnancy with preeclampsia. Hyperemesis was associated with a significantly increased risk of HER2‐enriched tumours (HR = 1.76, 95% CI: 1.07–2.87), but not with other intrinsic subtypes or breast cancer risk overall. These results provide evidence that preeclampsia is associated with a decreased risk of premenopausal and HER2‐enriched breast cancer and that hyperemesis, although not associated with breast cancer risk overall, may be associated with raised risk of HER2‐enriched tumours.

What's new?

Although the link of preeclampsia and hyperemesis gravidarum with altered sex hormone levels is well established, relatively little is known about the association of these pregnancy complications with breast cancer risk. Here, the authors found that a history of preeclampsia decreased the risk of premenopausal breast cancer and tumors enriched for the receptor tyrosine‐protein kinase HER2. In contrast, hyperemesis gravidarum increased the risk to develop HER2‐enriched tumors, pointing to nuanced differences of sex hormone alterations during pregnancy with respect to breast cancer subtypes and menopausal status.