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Research investigates the consequences of maternal caffeine intake for children's development

Study reveals correlation between caffeine intake levels and anthropometric measurements of babies aged six months and under
Research investigates the consequences of maternal caffeine intake for children's development

During pregnancy, caffeine easily crosses the placental barrier - Picture by Christian Glatz/Flickr CC-BY-NC-ND-2

Author: Amanda Hamermüller

Some people prefer coffee, others tea. There are those who opt for soda. Plenty is the number of methods to keep focus on a routine that becomes more and  more troublesome  and tiring. What, however, do these products have in common? Caffeine.

When we ingest products with a considerable amount of caffeine, we become more attentive and we can work better - an achievement to anyone who needs to have high performance for a long period. This happens because in less than 20 minutes, caffeine reaches our cells, increasing the influence of a neurotransmitter called dopamine, which is a natural stimulant for the nervous system. Lack of dopamine might cause depression, while the excess of it may cause agitation.

If people in general must be  careful with their daily intake of caffeine, the restriction for pregnant women are even greater. According to Michele Drehmer, a nutritionist specialized in maternal and infant nutrition,  coffee, soda, tea, mate, energy drinks, and even chocolate should be cautiously consumed up to a maximum daily amount. “The National Academy of Medicine suggests a 300mg intake of caffeine for pregnant women, which we follow here in Brazil”, Drehmer explains. The nutritionist made a intake simulation. “For you to have an idea of how much 300mg represents, we can say that four small coffee cups (50ml), a Coca-Cola can (335ml), an a piece of milk chocolate (60g) add up to 297 mg of caffeine”.

She explains that experimental studies on animals showed that caffeine crosses the placental barrier and it might rise the risk of congenital abnormalities, leading to miscarriage. Derhmer stresses that interventional studies of caffeine intake and its effects cannot be done in humans due to ethics, since a pregnant woman would never be exposed to caffeine. Existing evidence comes from observational studies, which prove that the risks for the baby are higher when the mother consumes caffeine in excess  while pregnant. “A systematic literature review shows that a higher caffeine intake is associated with higher frequency of miscarriages, fetal death, low birth weight, and small for gestational age babies”.

Thamíris Santos de Medeiros, a nutritionist, presents in her thesis a study about the impact of maternal caffeine intake during pregnancy on the anthropometric measurements - such as weight, body length, and skinfold thickness - of a child’s first months of life. She stresses that there are only a few studies researching children this young. “My aim was to investigate this initial period of life”, she says. She tells she has always been interested in maternal and infant nutrition: “During college, I always would do internships in which I could work with children, and my graduation project also focused on this area”.

From gestation, the body composition of a newborn reveals his or her health quality. Another indicator is the nutritional evaluation during first infancy, which is essential for diagnosing babies’ health state, that includes their growth and development. This diagnosis is also composed by certain anthropometric parameters of the newborn’s early months of life, mainly weight and full body length. Subcutaneous adiposity index is another criterion for the evaluation, as the body fat is measured through the skinfold thickness.

In her research Medeiros shows that caffeine easily crosses the placental barrier during pregnancy and neither the fetus nor the placenta has  the main enzyme that metabolizes the substance, which leads to exposition to caffeine and its deposition in fetal tissue. Furthermore, caffeine is highly soluble in fat and  it can also be absorbed by the fetus through the digestive system, since fetal glomerular filtration - the first stage in urine production - is still developing.

High levels of caffeine may interfere with the necessary amount of nutrients needed by the  fetus, the researcher explains. “Caffeine may lower  blood flow, causing the fetus to receive less blood and less nutrients, consequently leading to underdevelopment”. Observational studies show an association between maternal caffeine intake during pregnancy and birth weight reduction. For each additional 100 mg of caffeine (equivalent to one cup of coffee or two cups of tea) in daily intake, there is an increase of 3% in  low birth weight risk, especially when associated with smoking.  According to Mendes, smoking speeds caffeine metabolization, compared to the metabolism of a non-smoking woman.  (smokers metabolize caffeine faster than non-smokers, which deprives  the fetus of important nutrients, making the baby’s development more difficult.

Maternal metabolic diseases, such as diabetes and hypertension, may intensify the effects of caffeine on the fetus. Medeiros calls attention to the risk of caffeine interfering in the cell development process.  Experimental studies using rats have proved that caffeine intake during prenatal period leads to alterations in the glycemic metabolism and increases insulin resistance, which may contribute to the development of metabolic syndrome after birth.

The study also unveils how common it is for pregnant or childbearing-aged women to eat food containing caffeine. According to the research, the last Brazilian census appointed that the average caffeine intake was around 120 ml per day among adult and teenager women.  Drehmer attentively observes caffeine intake before pregnancy: “A study conducted by American nurses, one of most the important observational studies in the area, evaluated  more than 15 thousand women  for eighteen years. They observed that those who drank more than four cups of coffee per day before pregnancy faced higher risk of miscarriage, especially between the eighth and the nineteenth weeks”, she explains.

With regard to weight gain, the nutritionist explains that maternal caffeine intake might be related to weight gain as the child grows older: “Caffeine interferes in the brain activity that commands  appetite control and satiation. It could drive  the child to gain weight  throughout life.”


The study

This study is  associated with The impact of perinatal environment variation on the health of the newborn's first six months project [Impacto das Variações do Ambiente Perinatal Sobre a Saúde do Recém-Nascido nos Primeiros Seis Meses de Vida (IVAPSA)]. In the project, Medeiros worked in collaboration with a team of UFRGS professors and postgraduate students, and graduate students with a scientific initiation scholarship from other universities.

Medeiros and the research team chose to have only coffee as the source of caffeine intake. They based their decision on studies that show that the effects of caffeine are stronger when only this source is considered in the experiment.

They invited mothers with different medical background to participate in the study. The invitation was made to those who attended the following hospitals in Porto Alegre (Southern Brazil): Hospital das Clínicas, Hospital Nossa Senhora da Conceição, and  Hospital Fêmina Hospital. HIV positive women, women less than 37 week pregnant, and mothers whose newborns suffered from  congenital disorders  or needed hospitalization were not included in the study.  The study was carried out with 272 mother-newborn pairs, which were divided into  5 categories:

  1. Diabetic patients - 41 people;
  2. Hypertensive patients - 26 people;
  3. Smokers - 68 people;
  4. Mothers whose children were born small for the gestational age with no apparent reason (25 people); and
  5. Control group composed by women that did not have any of the above mentioned characteristics - 112 people.

The variability in the figures for each group was due to difficulties to find pairs for certain groups, refusal  of the invitation, and losses for not conducting interviews within the planned period. By the end of the study, there were  263 pairs.

In a period of 24 to 48 hours after birth, they collected the mother’s prenatal data, such as weight before pregnancy, height, weight after nine months of pregnancy, and information about the children’s birth. Seven days later, the research team interviewed the mothers at their homes, in order to collect data about their eating habit while pregnant; they were mainly concerned about caffeine intake during pregnancy. In the children’s third month of life, the researchers got in touch with the families to measure the babies’ weight, length, and skinfold. When the children reached six months of age, the same measurements were taken again.



There was a significant difference among the groups in relation to caffeine intake. The study confirmed that tobacco smoking is associated with higher caffeine intake, as the smokers group consumed up to 150 mg day, which was the highest rate among all the groups. High caffeine intake was also observed in the group composed by small-for-gestational- age children, with 128,2 mg/day, which shows the correlation between  low birth weight and caffeine intake during pregnancy.  While the group composed by diabetic mothers consumed 96,4 mg, the hypertensive mothers group consumed 136,6 mg, and the control consumed ;  91,3 mg  of caffeine per day.

With regard to anthropometric measurements, the average birth weight was 3,1kg and average body length was 48,5 cm. This study proved that children from diabetic mothers have birth weight significantly higher in comparison with that of children from other groups. It does not mean they are more prone to develop  macrosomia - excess of birth weight. Their case is different from children with intrauterine growth restriction (IUGR), who have lower weight and  shorter body length at birth. This research presented the significant difference of birth weight and length among children born small for-gestational age: up to 1kg lighter and 1.9 cm shorter than children from other groups.

An interesting fact emerged from the smokers group. Tobacco smoking during pregnancy is normally associated with low birth weight; however,  this assumption was not confirmed in this study. Despite the fact that children presented lower birth weight, the difference was not significant. Medeiros believes this is due to the limited number of participants in the smokers’ group.

Results  confirm the effects of maternal caffeine intake on the anthropometric measurements only in the control group.The researcher explains that the growth speed is higher in the first quarter than in the second quarter of the baby’s life,  which might affect skinfold measure since this is only visible in the baby’s first months of life. She reinforces that these results contribute to investigate whether infant weight excess is influenced by high caffeine intake.

In the diabetic mothers group, there was no significant difference between weight, body length, skinfold, and anthropometric measures when comparing children whose mothers took caffeine with hose who did not.

Medeiros stresses that the first thousand days of life are crucial for human development;  therefore further research analyzing the impact of certain habits on the child’s life is required. “It is a period in which the newborn’s body is still developing”, she says.

The researcher expects that the study may bring  social contribution: “I expect to call the attention of those who work in this field”. Medeiros says it is important to  raise awareness  to this type of research, and she believes that one day it will have an impact on pregnant women’s health treatment. “Consuming caffeine could become a behavior to be watched in the clinical practice, leading to similar warning as that of smoking or consuming alcohol during pregnancy”.


Master's Thesis

Title: Consumo materno de cafeína durante a gestação em diferentes ambientes intrauterinos e sua relação com medidas antropométricas de crianças nos primeiros meses de vida

Author: Thamíris Santos de Medeiros

Advisor: Clécio Homrich da Silva

Department:  Postgraduate Program in Children and Adolescents’ Health


Original text in Portuguese is available at < >.


Translated by Ana Cristina N. Nachtigall under the supervision and revision of Professor Márcia Moura da Silva (UFRGS).

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