Table of Contents
In the last lesson I discussed various aspects of the preconception time period that pertain to childhood weight outcomes. In this and the next lesson I will do the same with the pregnancy period.
During pregnancy there are several factors that can impact a child’s health, both during the pregnancy and then throughout life. In this lesson I will more specifically discuss the influences of maternal nutrition, weight status, and weight gain during pregnancy. I will discuss other aspects of pregnancy in the next lesson.
I want to make this very clear; I am trained as a pediatrician, not as an obstetrician-gynecologist, and I do not have the appropriate training needed to confidently tell you what lifestyle choices to make to have the “best” pregnancy possible. I am providing information in these lessons that pertain to child health outcomes, and more particularly child weight management. You should not make any significant changes based on what you read here without first speaking with your own OB-GYN provider.
Note: I will discuss several aspects of pregnancy in this and the next lesson, and it is interesting to consider the underlying mechanisms by which maternal health and lifestyle factors can influence long-term child health and weight outcomes.
A 2021 review detailed the various brain networks that influence the interaction between satiety, reward, visceral, and salience signals in the body.(Rasmussen, 2021) The authors describe various animal model and human literature that discuss how these brain networks can be influenced prenatally, leading to long-term implications related to obesity and other health risks. This “fetal programming”, or general response to “suboptimal” conditions leading to maladaptive changes in the long run, can occur secondary to maternal stress, unhealthy or excessive maternal nutrition, poor maternal metabolic health, and maternal inflammation. The resulting structural and functional brain adaptations can promote changes to the appetite-regulating networks, energy balance pathways, and executive functioning.
While not fully comprehensive, it seems at least some of the pregnancy effect is due to inducing changes within the brain itself. This may seem unfortunate, but there may be a glimmer of hope here. While speculative on my part, as the brain is more “plastic” (meaning able to adapt and change) earlier than later in life, this indicates to me it may be even more important to help enforce good health habits in young children, not only to establish good patterns for later in life but to potentially help reverse any negative influence of the prenatal period on brain development. We will need to await more studies to determine if any other concrete steps can be taken to reverse any negative fetal programming effects that occur during pregnancy.
The saying goes “you are what you eat”; whatever a pregnant woman eats will have a significant impact on the embryo and fetus as this is what will provide energy and building blocks for growth.
Interaction of maternal diet with child food preferences
During pregnancy the embryo and fetus are constantly exposed to amniotic fluid and a part of growth is dependent on actually swallowing this fluid. It turns out that several of the flavors that are consumed in food during pregnancy are transferred to the amniotic fluid. Therefore, the growing child is constantly exposed to a variety of flavors based on which foods and drinks are consumed by Mom. By the 3rd trimester a fetus will increase or decrease swallowing based on chemosensory changes of amniotic fluid.(Ventura, 2021) As recently reviewed, many studies show this can actually influence infant and child taste preferences, though studies show variable impacts based on the time point and duration of exposure.(Spahn, 2019; Ventura, 2021; Ustun, 2023) Thus, it may be helpful for pregnant individuals to consume a variety of healthy foods, not just for their own health but to also aid the child in accepting these flavors during the early childhood years.
However, this may work both ways. For example, a recent review included a handful of studies showing that when pregnant women regularly consume non-nutritive sweeteners this may increase the risk of the child developing overweight and obesity.(Sylvetsky, 2018) It is not clear yet if this is due to increasing a child’s preference for sweet tasting food or if this has some sort of developmental programming influence on body weight regulation, and more studies are needed to confirm this is a true effect, but it may be prudent to avoid excess exposure to non-nutritive sweeteners while pregnant.
Tip: While not explicitly shown in the above literature, it may also be a good idea to avoid too much added sugar while pregnant. Regardless if this helps to decrease child preferences for sweet substances, this may help prevent the onset of gestational diabetes mellitus (“GDM”). In a 2021 study, maternal sugar-sweetened beverage consumption during pregnancy was one of six risk factors found to significantly increase the risk of early adolescence overweight & obesity as well as metabolic syndrome.(Hu, 2021) If curious, the other risk factors were maternal prenatal smoking, excess gestational weight gain (“GWG”), breastfeeding duration, the timing of complementary food introduction in infancy and infant sleep duration.
Interaction of food intake with child health outcomes
A 2018 study assessed the influence of “loss of control” (“LOC”) with eating during pregnancy (measured by self-report) on various weight outcomes.(Micali, 2018) 5.2% of the women reported frequent LOC (“fLOC”) while 31.1% reported occasional LOC (“oLOC”). Those with fLOC had 3.74 kg greater GWG than those with no LOC while those with oLOC were in between. Children of those with fLOC had 2.02 higher odds of developing overweight/obesity in adolescence. Having oLOC did not lead to increased child weight relative to not having any LOC with eating. Importantly, when only examining women without preconception obesity the results were similar (fLOC had 1.92 higher odds in this setting); thus preconception obesity was not a factor in the association of fLOC with child overweight/obesity.
A 2020 meta-analysis (“MA”) of 15 cohort studies examining caffeine intake during pregnancy found that for every 100 milligrams/day intake there was a relative risk of 1.07 for low birth weight and 1.31 for childhood overweight/obesity.(Jin, 2020) Thus, avoiding excess caffeine intake during pregnancy may be wise, and a general recommendation is to keep intake at <200 milligrams daily.
A 2022 SR found an increase in BMI z-score of offspring at age 1 year, in early childhood, and in mid-childhood with greater amounts of non-nutritive sweetener intake during pregnancy.(Li, 2022) However, only 2 or 3 studies contributed to each of these analyses, so it is unclear how robust these findings will be as more research is conducted.
A 2019 review highlighting various aspects that influence the development of offspring adipose tissue (this is the medical term for body fat) noted that low protein consumption during pregnancy correlates with intrauterine growth restriction in humans and may ultimately increase the risk of obesity later in life.(Rodgers, 2021) A separate 2019 review noted that balanced energy protein supplements for underweight pregnant women were helpful to prevent infants being born small for gestational age (“SGA”) while they were helpful in underweight and normal weight women to prevent low birth weight.(Grobler, 2019) On the other hand, high-protein supplement intake in normal weight women led to an increased risk of SGA.
Tip: The above guidance indicates eating a variety of different foods and flavors with balanced protein intake is overall beneficial. Couple this with the general nutritional advice in the Nutrition and Weight Management course and it seems that eating a variety of healthy food group items with a relatively balanced macronutrient intake is desirable. Importantly, this advice may seem like common sense, and if it does that is likely a good thing as it would be surprising if completely altering typical healthy eating habits proved increasingly beneficial for child health outcomes.
Consuming a balanced diet may also help stave off loss of control with eating; anecdotally, loss of control seems to occur more frequently in individuals who are restricting intake in some way. Eating a wide variety of foods and not placing complete restrictions on anything in particular may decrease the urge to eat large amounts of food at once.
Maternal weight status throughout pregnancy
In the last lesson I indicated that parental obesity prior to conception can increase the risk of offspring obesity. Here I’ll summarize some of the recent literature describing how maternal weight status and weight gain throughout pregnancy can influence offspring health risks.
Impact of maternal obesity on child health
A 2020 review of human studies evaluated the impact of overweight/obesity during pregnancy and its influence on offspring health.(Dow, 2020) With maternal obesity there are increased offspring risks of:
- a variety of congenital anomalies (ie, orofacial clefts)
- metabolic abnormalities (obesity, insulin resistance, elevated leptin and inflammatory markers, type 1 & type 2 diabetes, nonalcoholic fatty liver disease, and alterations in the microbiome)
- early menarche (even after adjusting for prepubertal body mass index (“BMI”))
- allergy/immunologic issues such as asthma and eczema
- cognitive & behavioral issues such as depression, learning disabilities, and attention deficit hyperactivity disorder
- other conditions such as cerebral palsy, epilepsy, and leukemia
A 2021 Guideline from the International Federation of Gynecology and Obstetrics on the management of preconception, pregnancy, and postpartum obesity noted that(McAuliffe, 2020):
- Similar to above, maternal obesity can increase the risk of the offspring developing obesity, type 2 diabetes mellitus, and neurodevelopmental disorders.
- Maternal obesity can increase the risk of stillbirth and other pregnancy complications leading to more frequent c-sections and is also associated with decreased breastfeeding.
- The authors note many of these health risks likely start with maternal overweight.
A 2020 review on the cardiometabolic impact of perinatal exposure to maternal obesity noted the following(Kislal, 2020):
- Maternal obesity increases the risk of childhood obesity independently of separate genetic, familial, and environmental effects as seen in paired-sibling studies.
- Maternal obesity associates with neonatal adiposity at birth and subsequently with childhood adiposity but not with neonatal lean body mass.
- Two studies have found that newborns of mothers with obesity have increased intrahepatocellular lipid deposition (meaning increased fat in the liver).
- A couple longer-term studies have found that maternal obesity confers an increased risk of coronary heart disease as well as all-cause mortality in offspring when they reach adulthood.
- While there are associations of maternal obesity, excess GWG, and maternal metabolic syndrome on child cardiometabolic risk factors, these associations seem to be mediated by child adiposity.
Note: I want to emphasize a key point that I placed in bold from the last review above; a lot of the negative health associations from maternal obesity during pregnancy seem mediated by child adiposity. Thus, instead of the risk being from maternal obesity during pregnancy directly, what seems to occur is:
Maternal obesity during pregnancy -> increased body fat in childhood -> longer-term health issues
This is very important, because it implies that maternal obesity during pregnancy does not mean the negative health effects are inevitable. Rather, it makes the negative health effects more likely by increasing the risks of childhood obesity and excess body fat. This is further supported by a 2023 SR/MA that found offspring of fathers with overweight or obesity had similar BMIs to offspring of mothers with overweight or obesity, implying the intrauterine environment is less relevant.(Zhang, 2023) Thus, if we can prevent or successfully treat childhood obesity then there may not be many long-term negative health effects at all. In Lesson 8 I further discuss the impact of childhood obesity on future health and the benefit of treating this to reduce adult health risks.
Physiologic changes in pregnancy and in the offspring due to maternal obesity
As recently reviewed, there are several physiological aspects that may contribute to the above health associations(Reichetzeder, 2021):
- Normally in early pregnancy there is an increase in insulin sensitivity that promotes the uptake of glucose into adipose tissue; this promotes an increase in energy intake which is needed to support the pregnancy. Later in pregnancy relative insulin resistance develops to increase blood glucose transfer to the fetus.
- However, obesity-related preconception insulin resistance increases the risk of developing GDM and can lead to an increase in blood cholesterol and triglyceride levels later during the pregnancy.
- Pregnant women with normal weight have net lipogenesis (synthesis of fatty tissue) early in pregnancy (to store energy for the pregnancy) but net lipolysis (breakdown of fatty tissue) late in pregnancy. However, pregnant women with obesity may have net lipolysis in all stages of the pregnancy. This can lead to lipid accumulation in the placenta, alterations in placental metabolism and function, and can continuously expose the fetus to high levels of free fatty acids.
- Separately, maternal obesity also leads to mitochondrial dysfunction which can cause a deficiency in placental hormonal output.
- In animal studies there is also a lot of evidence that epigenetic alterations occur; this can influence child health risks by distinct pathways from the physical changes noted above.
In a 2019 review of intrauterine programming of obesity and type 2 diabetes mellitus the authors noted that in animal studies diet-induced maternal obesity can alter offspring dopamine and opioid-related gene expression in the brain (in particular within the mesocorticolimbic reward pathways & the hypothalamus) to aberrantly program feeding behavior.(Fernandez-Twinn, 2019) This may cause people to perceive greater joy with food intake, particularly with highly palatable food, and may make them more prone to overeating. A separate review examining animal models collectively found that maternal obesity leads to differences in hyperphagia & reward-based pathways associated with eating, malprogramming of the hypothalamic satiety set-points, and alterations of skeletal muscle, adipose tissue, the liver, and the pancreas to more pro-inflammatory and insulin-resistant phenotypes.(Kislal, 2020)
A 2021 review describing the influences of metabolic programming of offspring adipose tissue noted that maternal obesity has been shown to alter the composition of offspring lipids, myocytes, gene expression, and oxidative stress levels.(Rodgers, 2021) Thus, it seems that infants of mothers with obesity not only may have an increased quantity of adipose tissue but the quality itself of their adipose and other tissues may differ as well.
Note: It seems much of the excess risk of adiposity and health issues in children born to mothers with obesity may stem from alterations in feeding behavior as well as potential alterations in the quality of various organ systems. However, there is no indication that these alterations are permanent and cannot be changed. In Lesson 8 I will show literature demonstrating that appropriately treating childhood obesity will largely mitigate adult health risks. While it may be more difficult to achieve and maintain a healthy weight with aberrant fetal programming, that does not mean it is impossible; it just may require more conscious effort for some individuals than others.
Impact of excess gestational weight gain (“GWG”)
Besides obesity, another consideration is the degree of weight gain during the pregnancy itself. A 2020 study examined the relationship between elevated GWG and birth weight as well as 3-year obesity outcomes when including sibling analysis (to help identify the impact of the GWG vs. shared environmental contributions).(Badon, 2020) The authors used the 2009 Institute of Medicine (“IOM”) GWG recommendations to classify women as gaining an appropriate amount, too much, or too little weight. That guideline suggests to aim for:
- GWG of 28-40 pounds for pregnant women with underweight.
- GWG of 25-35 pounds for pregnant women with normal weight.
- GWG of 15-25 pounds for pregnant women with overweight.
- GWG of 11-20 pounds for pregnant women with obesity.
In this study, 24% of women gained less than the IOM recommendations, 33% met the recommendations, and 43% exceeded the recommendations. The authors found:
- Those who gained less than the recommendations (compared to those who met the recommendations) had infants who were generally smaller with 59% greater odds of being born SGA and 43% lower odds of being born large for gestational age (“LGA”).
- In contrast, those who exceeded the recommendations relative to those who met them had infants who were generally larger with 35% lower odds of being born SGA, and 88% greater odds of being born LGA.
- When examining outcomes at 3 years of life, looking at the children in isolation there was an association between GWG and obesity outcomes, but when accounting for the sibling analyses these associations disappeared.
- Thus, it seems that excess GWG alone does not influence long-term obesity outcomes and any association is likely due to shared environmental factors.
- As an example, if the family typically eats a lot of fast food and this contributed to excess GWG, and the family continues to eat a lot of fast food after the child is born, then it may be the excessive consumption of fast food rather than the excessive weight gain during pregnancy that would lead to the child developing obesity.
Even though excess GWG may not impact the future obesity risk of the child very much, it can still impact the pregnancy and birthing process significantly, which can have significant health implications. A 2021 systematic review (“SR”) noted that prior research indicates every 1 kg excess in GWG is linked to a ~10% increased risk of adverse pregnancy outcomes; this risk is exacerbated in individuals with preconception obesity.(Harrison, 2021) Additionally, the authors note that women typically retain ~2-5 kg per pregnancy; if this number is increased with excess GWG then this will make them more prone to having obesity for a subsequent pregnancy. In the actual SR the authors analyzed 22 clinical practice guidelines regarding weight management across the preconception, pregnancy, and postpartum periods, finding the guidelines were quite variable and many did not provide explicit advice regarding steps to take to help ensure appropriate weight gain.
A 2021 Guideline from the International Federation of Gynecology and Obstetrics on the management of preconception, pregnancy, and postpartum obesity noted that the IOM GWG guideline is widely followed but there is some indication of reduced risk of pregnancy complications when women with obesity gain <5 kg (<11 pounds, the lowest point of the IOM recommended weight gain range for pregnant women with obesity).(McAuliffe, 2020) The authors note one guideline in Japan recommends gaining <5 kg for pregnant women with obesity.
Tip: Even if excess GWG does not contribute significantly to future child obesity risks, as indicated above it is still a good idea to avoid this to help decrease the risk of pregnancy complications (ie, developing GDM or preeclampsia) and also to make it easier to lose the excess body weight postpartum.
Additionally a 2020 SR/MA found that interpregnancy BMI gain increased the rate of GDM, gestational hypertension, c-section, preeclampsia, and LGA, with a bigger increase in risk for the first 3 outcomes in women who started as underweight or normal weight prior to weight gain.(Timmermans, 2020) An interpregnancy BMI decrease lowered the risk of LGA and in women with overweight/obesity it also decreased the risk of GDM. Weight loss increased the risk of SGA in women who initially were underweight or normal weight. Regardless of initial BMI, weight loss increased the risk of preterm birth.
Thus, several pregnancy outcomes which can influence child health are negatively impacted by interpregnancy weight gain, and GWG is included in interpregnancy weight gain assuming it is not lost after delivery. Therefore, there are several health benefits towards the current pregnancy for avoiding excess GWG and these benefits can extend to future pregnancies as well.
In this lesson I presented literature discussing the various implications of maternal food intake and weight status (as well as weight changes) during pregnancy on childhood obesity risk. The key takeaways are:
- Eating a variety of healthy foods and flavors with a balanced macronutrient profile should promote positive child health outcomes and expand the child’s flavor preferences. For the same reason it may be best to avoid high amounts of sugar (additionally, this may help prevent gestational diabetes).
- Gaining gestational weight within the guidelines will help prevent gestational diabetes, decrease the risk of birth complications, and help prevent excessive weight gain prior to a subsequent pregnancy.
- Much of the negative health impact seen from the risk factors described above seems to be mediated by an alteration of appetite regulation and childhood adiposity; thus, when the child is born if good habits are established and childhood obesity can be prevented from an early age there is little reason to think any negative prenatal influences will carry forward into adulthood.
In the next lesson I will discuss additional pregnancy considerations, including medical conditions, pregnancy number, delivery method, birth size, environmental exposures, and pregnancy interventions regarding healthy lifestyle changes.
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- Zhang J, Clayton GL, Overvad K, Olsen A, Lawlor DA, Dahm CC. Body mass index in parents and their adult offspring: A systematic review and meta-analysis. Obes Rev. 2023 Oct 2:e13644. doi: 10.1111/obr.13644. Epub ahead of print. PMID: 37783229.