Abstract
The idea of intrauterine or fetal factors being the cause of several prevalent noninfectious diseases in adults has recently gained the status of an axiom. One of the most thoroughly studied predictors is birth weight (BW). Although many published studies point at relations between BW and later adult morbidity or mortality, much less attention is paid to associations between baby BW and maternal morbidity. Available data suggest a sort of dichotomy in these relationships. Thus, cardiovascular risk is higher in mothers of babies with a reduced BW, while cancer risk, mainly of the breast and some other hormone-dependent cancers, is often higher among mothers of babies with a large BW (newborn macrosomia). This review addresses possible causes and endocrine mechanisms of this topic and suggests a ‘particular’ and ‘general’ solution for arising controversy. Emphasis is placed on a probable competition between chronic diseases (mainly, between female hormone-related cancer and cardiovascular pathology) within the concept of multiple causes of death. These associations should be remembered while studying the relation between offspring BW and maternal predisposition to hormone-associated cancers and other noncommunicable diseases.
Keywords
Although many chronic diseases including cardiovascular disorders and cancer are more common in older adults, their causal factors often occur during the earlier stages of ontogenesis. Therefore, deviations in the physical parameters of newborns are often viewed as the first signs of apparent or, more often, occult pathology of both the child and mother [1]. The importance of these factors to the child is partly reflected by popular concepts such as thrifty genotype, thrifty phenotype, developmental plasticity, compensatory or ‘catch-up’ growth and fetal programming [2–9]. The ‘fetal, or developmental, origin of adult diseases’ is currently in the focus of attention [3,10–12]. Its significance is confirmed by multiple published studies often based on integral indices, such as birth weight (BW) at term. The occasionally published critique of these views does not compromise the general idea of human noncommunicable diseases as a complex condition originating, at least partly, from in utero factors [13,14].
However, some of the critical arguments are quite convincing, leading to the “causal inference in this domain remains a serious challenge” and “the reported associations may be biased rather than causal” conclusions [15]. In a comment to a large Danish publication regarding U-shaped rather than linear association of BW, with later adult mortality owing to circulatory diseases and other causes [16], Basso pointed, that “we should be cautious to not focus excessively on fetal growth,” while speaking of adult outcomes [17]. In another commentary to the same paper Lawlor added that, “This area of research needs to move away from simply describing the association of BW with disease/health outcomes. Instead, we must aim to understand whether there are modifiable risk factors during the developmental period that are importantly causally related to later disease outcomes” [18]. Therefore, the discussed subject should be reviewed in all its complexity, taking in account the mechanisms and possible factors leading to the development of chronic noninfectious conditions, such as cardiovascular diseases (CVDs) and hormone-associated cancers.
Meanwhile, the ‘birth weight is forever’ concept is still popular [17], not only because BW is an important indicator of both biological traits and socioeconomic circumstances [19], but also because of its apparent relationship with distant manifestations of human pathological conditions, although its exact machinery is not yet clear [1,20]. Moreover, as the attention of ‘developmental origin of chronic noncommunicable diseases’ proponents is traditionally focused on low BW (LBW) babies, they mostly overlook the opposite side of the weight spectrum. However, recent trends suggest that high BW (HBW; more than 4000 g at birth) babies are becoming more prevalent than LBW babies [21,101]; hence, the HBW group is beginning to attract more attention.
This review is based on long-term experience of studying chronic disease-related aspects of HBW [20,22]. After a brief discussion of BW relation to later adult pathological conditions, the article will mainly concentrate on the other side of the problem: the association of babies’ BW with the morbidity of their parents, particularly their mothers. Finally, possible causes of opposite associations of newborn macrosomy with maternal morbidity rate due to hormone-associated cancer and CVDs will be discussed.
BW & liability for adult conditions including cancer & CVDs
During the late 1980s, when the first papers describing relations between BW and adult diseases were published [3,13,23–25], the total number of relevant publications exceeded several hundred. The main discussion points included the relationship between BW and subsequent all-cause mortality, diabetes prevalence (with more emphasis placed on glucose intolerance and insulin resistance than metabolic syndrome and obesity) and most of all, morbidity and mortality due to cardiovascular conditions and cancer. Although the connections between cancer and developmental issues in the beginning ‘were in the shadow’, the later studies highlighted this subject's importance [13]. Since our review is focused mainly on few quite specific aspects of the matter, the mentioned topic is illustrated by two recently published meta-analyses, chosen among many available sources [26,27].
One meta-analysis is based on data presented in 22 publications on the associations between BW and adult all-cause mortality due to CVDs, and cancer [27]. The analysis only included studies of the relationship between hazard ratios (HRs) and 95% CIs per BW increase measured in kilograms. BW associations with all-cause mortality were established based on ten studies (12,995 deaths among women and 23,839 deaths among men), CVD mortality association analysis included nine studies (2796 cardiovascular deaths in women and 8570 in men), while BW and cancer-related mortality association was assessed using data from five studies (4208 cancer deaths in women and 4176 in men). The observations revealed a decrease of all-cause death risk with an increase in BW (HR: 0.93 for females and HR: 0.95 for male population). Higher all-cause mortality was discovered in a population with a relatively LBW (i.e., less than 3000 g; sex-adjusted HR: 1.11), while there was no evidence of an association between HBW (more than 4000 g) and all-cause mortality changes when compared to the reference group of 3000–4000 g (HR: 1.02). Meta-analysis of cardiovascular mortality showed a reduction of risk per kg increase in BW in both women and men (HR: 0.88). On the contrary, a higher BW in men was positively associated with cancer mortality (HR: 1.13 per BW kg), while in women there was no strong evidence of such a connection (HR: 1.04) [27]. Although these results pointed at the possible gender-based differences in cancer morbidity, it should be noted that the analysis performed by Risnes et al. did not include the connection between BW and breast cancer incidence in females, reviewed in detail later [27].
Indeed, in the other meta-analysis, the authors focused on adult breast cancer incidence and birth parameter relationships, including weight (kg), length (cm), head circumference (cm), and ponderal index (defined as weight [kg]/height [m3]). The data on over 22,000 females with breast cancer and 604,854 noncases from 32 epidemiological studies was analyzed [26]. The analysis was restricted to singletons divided into several BW groups of <2500, 2500–2999, 3000–3499, 3500–3999 and >4000 g. A 0.5-kg increase in BW was associated with a statistically significant increase of breast cancer risk in studies based on birth records (pooled relative risk: 1.06; p = 0.002). Higher breast cancer risk was also associated with increased newborn length values (17% higher in women with newborn length of more than 51 cm) and birth head circumference (11% higher in women with birth head circumference of more than 35 cm), while it had no connection to ponderal index value (relative risk: 1.01). The association with BW became insignificant after adjustment for birth length and head circumference, while the association with birth length persisted after adjustment for BW and head circumference. These findings were consistent with positive associations at both pre- and post-menopausal ages, and did not appear to be confounded or modified by known breast cancer risk factors. As a whole, these facts gave evidence of the independent role of newborn macrosomy in breast cancer development [26]. Assuming causality, the authors came to the conclusion of a possible connection between high birth parameter (i.e., a BW more than 3.5 kg) values and approximately 5% of all breast cancer cases in developed countries, in contrast to previously stated inverse associations between BW and adult all-cause mortality, especially due to circulatory diseases [16,27].
Associations between BW and other adult cancers were addressed in several studies. In a cohort of more than 200,000 women and men, born between 1936 and 1975, a total of 12,540 primary invasive cancers were diagnosed during 6,975,553 person-years of follow-up. Analyses of site-specific cancers showed a positive linear association between most cancers (e.g., liver and kidney cancer, among others) and BW increase, although for testicular cancer this association was inverse, while pancreas and bladder cancer demonstrated a U-shaped connection. For breast cancer, relative risk was 1.07 in the group with BW >4500 g compared with 3000–3499 g in the reference group [28]. The results of this [28] and another study [29], while suggestive of a general trend toward a positive association between BW increase and adult cancer risk, pointed out some site-specific features compatible with differences between tissue targets, as well as between involved mediating factors, such as gender. Some of these factors are discussed in the following sections.
Opposite associations of HBW with maternal morbidity owing to cancer & CVDs
The aforementioned patterns are partly true not only for adults with a history of HBW, but also for their parents. Data on CVD and cancer incidence in both mothers and fathers are summarized in
Relationships between cardiovascular mortality/morbidity in parents and babies’ birth weight.
BW: Birth weight; CVD: Cardiovascular disease; HR: Hazard ratio; LBW: Low birth weight; RR: Relative risk; SD: Standard deviation.
Relationships between cancer mortality/morbidity in mothers and weight at birth of their babies.
BC: Breast cancer; BW: Birth weight; CVD: Cardiovascular disease; EC: Endometrial cancer; HBW: High birth weight; HR: Hazard ratio; LBW: Low birth weight; OR: Odds ratio; SD: Standard deviation; SE: Standard error.
The data presented in
These data are not clearly uniform, yet nine out of 14 studies report a positive correlation between cancer incidence in mothers and BW or other anthropometric values of their offspring. Several of the research groups also included fathers of the babies in the study, and in these cases no correlations were found. The variability of certain results in the population of mothers may be caused by differences in data input (e.g., in different publications the data could date back to the first or subsequent births). The studies also use different end points, such as cancer site or potential role of environmental factors (smoking-related vs smoking-unrelated cancers). The data on tumor localization seems most important, as among the nine studies showing evidence of BW and cancer incidence, positive correlations of most of the tumors were hormone-associated (breast cancer in eight studies, endometrial and ovarian cancer in two studies) with only one study mentioning hormone-independent cancer (leukemia) [42]. In some cases, the breast cancer morbidity association with baby BW was more evident in women older than 50 years [20,44]. This may drive one to conclude that the limited evidence for an overall connection between fetal growth and maternal breast cancer risk described in some of the papers may be explained, at least partly, by restriction of the study population to women younger than 50 years [43]. Such age-dependent differences in breast cancer incidence between mothers of babies with high BW can be most likely be attributed to disparities in the hormonal and metabolic background of pre- and post-menopausal breast cancer [20,36,44].
On the whole, the available data suggest that there is a positive correlation between cancers in mothers (predominantly breast cancer) and large BW in their babies. While this correlation contradicts the data on cardiovascular mortality in mothers (
Newborn macrosomy & cancer/cardiovascular morbidity: the endocrine & other mechanisms of dichotomy
The child's own life
The biological mechanisms connecting prenatal factors with adult diseases are still poorly understood [10,15,16,31,32]. Attempts to find causes for the inverse relationship between newborn BW and subsequent cardiovascular mortality in their adult life are based on intrauterine undernutrition, developmental plasticity and compensatory growth concepts [3,11,23]. In particular, potential roles of the key factors (e.g., neuroendocrine, immunological, inflammatory, oxidative and DNA-damaging) involved in chronic diseases are considered. Environmental factors, apart from nutritional ones, are gaining more recognition [12]. In addition, more attention has recently been given to the genetic and epigenetic factors influencing mortality trends among women with a history of LBW [31,34,46], as well as to the genetics of BW itself [47,48]. There have also been attempts to find a common base for impaired insulin-mediated growth of the fetus and insulin resistance in adulthood [49].
The prevalence of CVDs among the causes of death in adult women with LBW history compared with cancer deaths warrants the search for some additional explanations [13,27,50,51]. In particular, the increased risk of breast cancer in women with HBW may be influenced by the number and properties of stem cells during the intrauterine period, this factor relates to mammographic density in later life, the effects of excess estrogen levels on stem cells or the shift in the MAPK/estrogen receptor-α ratio in the mammary gland tissue [13,52–56]. However, these factors cannot be the cause of the positive association between BW and adult cancer mortality in men [27]. On the other hand, taking into consideration other hormone-like and growth factors (including IGF-1), epigenetic and genetic variations, ethnic differences, role of secular trend (acceleration) and some other assumptions, this research field looks increasingly important for understanding the relations between intrauterine factors and adult cancer morbidity [26,51–55,57,58].
Diseases in mothers
The aforementioned trends may partly refer to the relationship between BW in babies and mortality caused by the main noninfectious conditions in their parents, mainly mothers. Clearly, the degree of parental (mothers and fathers) involvement in intrauterine life of their children is different. Therefore, the effect of birth characteristics on newborns and each of the two parents cannot be the same (see [27] and data presented in

Health perspectives of high birth weight female babies and their mothers.
Some additional factors may be as specific, while having a distinct nature. In particular, giving birth to children who are small for their gestational age is associated with decreased placenta-derived angiogenic growth factors levels in maternal circulation and, thus, decreased angiogenesis and coronary circulation repair later resulting in ischemic heart disease [61]. This can also relate to cancers (including mammary cancer) as higher levels of angiogenic factors may stimulate tumor initiation or promotion in mothers of macrosomic children (the assumption could be checked experimentally).
Four decades ago, as we initiated our studies of HBW in babies as an early marker of hormone-associated cancer risk for their mothers [20,22,64], we were motivated by the concept of maternal hyperglycemia leading to fetal hyperglycemia and, consequently, to insulin hypersecretion in fetuses [65]. This complex cause–effect relationship may lead to a fetal weight increase due to increased fat accumulation [65] and metabolic predisposition to cancer, which was termed ‘cancrophilia’ [66,67]. We hypothesized that a history of giving birth to macrosomic baby (>4000 g) may be, at least partly, associated in female cancer patients with latent carbohydrate metabolism disturbances, since there was no evident increase in overt diabetes rate observed for cancer patients, including patients with breast or endometrial cancer, in comparison to female cancer patients, who had not delivered a large baby [20].
The significance of glucose intolerance as a stimulating factor for both macrosomy of newborns and predisposition of their mothers to cancer can hardly be denied, especially owing to the well-known association between diabetes and certain types of cancer [68]. However, considering the U-shaped (rather than the linear) relationship between weight at birth and diabetes-related maternal mortality [69], we later started looking for other explanations for dichotomy (here, the opposite type of correlation) between mother cancer and CVDs risks in relation to baby BW. Clearly, this controversy contradicted the belief, that insulin resistance, metabolic syndrome, glucose intolerance and body mass excess are common causal factors for the main noninfectious conditions (i.e., CVDs) and, at least, some cancers (breast, endometrial and colorectal) [70–72].
This dilemma may have a ‘particular’ and a ‘general’ solution. The particular solution concerns, for example, the potential role of excessive of estrogenic stimulation during the birth of HBW babies. Of note, although estriol is believed to be the main pregnancy-associated estrogen, the amount of more biologically active estradiol produced during pregnancy is also high, reaching 10,000 pg/ml by week 33 [73]. This may leave behind long-term ‘imprints’ manifested as initiation and promotion of occult breast tumors in mothers [40,44] and, also, as decreased maternal CVD risk [74].
The general solution may be reduced to the following reasoning [75]. In cases with multiple death causes (when the main cause is supplemented by additional ones with possible influence on lethal outcome [76]), ischemic heart disease as the main death cause is most often associated with diabetes mellitus and atherosclerosis, whereas cancers, including hormone-associated ones, are much more rare as comorbidity, located, in particular in females, behind stroke, asthma, tuberculosis and Alzheimer's disease [77]. The inverse relationship between mortality rates related to cancer and CVDs may be explained by gradual changes in morbidity structure and, more importantly, by competition and interaction between different diseases [78]. Thus, although the incidence of the main noncommunicable conditions increases with age, the rate of increase and disease combinations may have individual variations [75]. Since one of the crucial and integral intrauterine development markers, BW, has a positive correlation with cancer incidence (mainly breast and endometrial cancer) and a negative correlation with ischemic heart disease and hypertension in mothers, it mostly illustrates the general trend [77,78]. This general trend may be modified by endocrine-related ontogenetic features characteristic of separate individuals [5,10,12,20,64], and also by factors associated with heredity, ethnicity and different environmental effects [28,34,48,79]. However, speaking of breast cancer, one should note the fact that, as in many hormone-associated cancers, the pathogenesis of breast cancer concerns hormonal mechanisms, but also pathways based on DNA damage [80–82]. Nevertheless, as the genotoxic damage often needs hormonal backing to cause cancer (and it is, in particular, evident in patients with genetic predisposition to malignant growth [83,84]), this factor should be acknowledged as a legitimate additional answer to the question on how offspring macrosomy at birth can be predominantly related to maternal inclination for tumor development in hormone-dependent tissues; at the same time, the role of DNA damage in the initiation and progression of CVDs remains highly debated [85].
Conclusion
The concept of intrauterine or fetal origins of prevalent adult noninfectious conditions has recently gained the status of an axiom. This idea was strongly influenced by the discovery of a relationship between BW and subsequent ‘medical events’ in adult life [24,27,30]. There is also an association between a baby's BW and morbidity/mortality rates of their mothers due to cardiovascular conditions and some types of cancer (mostly hormone-associated). Moreover, these associations are different, are even the opposite [20,36,37,44,61]. These may have a distinct hormonal and metabolic background starting rather early (the initiation time may vary) and influencing both child and mother (Figure 1).
Thus, what conclusions can we draw from the abovementioned facts, taking into consideration the topic of this report? The founder of the currently accepted approach to the ‘fetal origin of adult disease’ and his coauthors have long believed that measures promoting pre- and post-natal growth are able to decrease mortality from ischemic heart disease [23]. As this approach was mostly focused on small newborns, it somewhat missed potential cancer-related threats associated with increased BW, revealed by other authors [15,17,86,87] and the authors of this article [22,88]. As time passed the approach gradually tended to become more balanced [12,57].
Therefore, while assuming the existence of associations between fetal development and later chronic noninfectious diseases emerging both in babies reaching adulthood and, as was expressly pointed in this article, in their mothers, we should have two objectives in mind. The first is achieving an optimal weight at birth (approximately 3400 g at 40 weeks in Caucasians [1]). The second is working out a reasonable approach to prevent hormone-associated cancers (mainly, breast and endometrial cancer) in mothers of macrosomic babies and cardiovascular conditions in women whose newborn babies are on the contrary often relatively small [12,18,20,52,53]. The question of whether such preventive measures are to be taken during pregnancy or in other periods has already been discussed (see, for example, [20,89,90]), although this is yet to be studied in full.
Future perspective
The peculiar point in babies’ BW association with distant/delayed pathological conditions is its relation to both baby's adult life and his or her mother's health.
In either case, those concerned in this specific area of women's health have to face, at present and in the future, not only biomedical, but ethical problems as well.
Since body weight at birth is, in a sense, recognized as a resultant and starting parameter, we should expect the prevalence of two research lines in the near future. The first will be focused, as one may foresee, on the identification of the most effective markers, mainly molecular and genetic ones, of HBW association with real cancer risk in mothers and causes of these associations. The second line will apparently be centered on finding the period of a mother's life when preventive interventions against potentially adverse events, possibly associated with high body weight of newborn babies, are most optimal and reasonable. The same is true for mothers in the opposite (LBW/CVDs) situation, while the change in trend in markers and preventive measures will obviously be needed.
Financial & competing interests disclosure
The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
No writing assistance was utilized in the production of this manuscript.
Executive summary
Many chronic diseases (e.g., cardiovascular diseases and cancer) are more common in older adults, but their causal factors often occur at earlier stages of ontogenesis.
One of the most thoroughly studied predictors in this area is birth weight (BW), which is considered an integral parameter for the evaluation of fetus–mother relations. Lately, a great deal of attention has been focused on groups of newborns with low and high BW.
Although there are many studies highlighting the relationship between BW and later adult morbidity or mortality, much less attention is paid to associations between baby BW and maternal morbidity.
The available data suggest a sort of dichotomy in these relationships. Thus, cardiovascular risk is higher in mothers of babies with low BWs, while cancer risk, mainly of the breast and some other hormone-dependent cancers, is often higher among mothers of babies with high BWs (newborn macrosomia).
This controversy contradicts the belief that insulin resistance, metabolic syndrome, glucose intolerance and body mass excess are common causal factors of the main noninfectious conditions (i.e., cardiovascular disease) and, at least, some cancers (breast, endometrial and colorectal).
While explaining this dilemma, the emphasis can be made on ‘particular’ (mother-specific) and more ‘general’ factors, namely on a probable competition between chronic diseases (first of all, between hormone-related cancer and cardiovascular conditions) in view of the multiple causes of death concept.
The general trend may be modified by endocrine-related ontogenetic features characteristic for separate individuals, and also by factors associated with heredity, ethnicity and different environmental effects.
