Effects of Caffeine in Fetuses or Pregnant Rats


Caffeine has been known to cause many deleterious effects starting from addiction to effects on the neurological development, skeletal development, and behavioral system of the offspring when the mother has consumed large quantities of it.

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Having gone through the various literature on the subject, I have decided to replicate the steps taken by Daniel S. Grossier, Department of Pediatrics and Institute of Human Nutrition, College of Physicians and Surgeons, University of Columbia. I intend to draw my own conclusions on the subject of the effects of caffeinated coffee consumption on pregnant rats and the neurological development and behavioral abnormalities observed in the offspring of these pregnant rats and comparing the effects with a group of similar pregnant rats which would be given decaffeinated coffee and another group which would be consuming plain drinking water.

Caffeine has been shown to penetrate the blastocyst or developing cell of the fetus and also accumulate in the fetal liver and brain. In adult animals, caffeine influences the metabolism of various neurotransmitters. It appears possible that prenatal exposure to caffeine could affect the brain function of the offspring as the brain development is maximum in the prenatal stage. So changes in the development of the brain could have a lasting effect manifesting as long-lasting behavioral abnormalities. My intention is to report the results of my study conducted in the rat where possible behavioral changes consequent to the consumption of caffeine during Pregnancy would be seen in it and its offspring. The results could be correlated to the effects of high levels of caffeine consumption in human pregnancies.

Literary Review

Evidence has been found to suggest that caffeine could have deleterious effects on fetuses should their mothers consume large volumes of coffee during their pregnancies. Scientists at Carleton University, in their study on the subject in 1985, found that children born to mothers who consumed more than 300mg per day of coffee had a lower birth weight and smaller head circumference than those born to other mothers who did not have this habit. Large amounts of caffeine could also produce cardiac arrhythmias. (Effects on fetuses and newborn children, New World Encyclopaedia).

Another study by Lawson et al. found that women who used large amounts of coffee during their pregnancies also had the tendency to have miscarriages more than those who never used coffee in this period. The exact minimum toxic dosage of caffeine that could cause damage to the fetus has yet to be specified. Caffeine damages the DNA. It has the ability to inhibit two DNA-damage response proteins;

Ataxia-Telangiectasia Mutated (ATM) and ATM-Rad50 Related (ATR). DNA damage frequently occurs in the dividing cells of the developing fetus. The two proteins control the cells’ ability to stop the cell cycle in the presence of damage like DNA single-double strand breaks and nucleotide dimerization (Effects on fetuses and newborn children, New World Encyclopaedia).

How does caffeine produce damage? It crosses over from the maternal blood into the fetal blood through the placenta. The caffeine could affect the fetal heart rate and breathing. Studies have been done which show that caffeine can cause premature birth and low birth weight. A study in 1988 showed that female infertility could be produced by an intake of 120-300 mg. of caffeine. However, a final conclusion could not be drawn as other variables were present. Caffeine has been found in breast milk.

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Breastfeeding mothers had better leave caffeine off their diet. Neligh and Derby in 1994 conducted a study and decided that the amount of caffeine in less than 5 five-ounce cups of coffee are not a problem for breastfeeding mothers and babies. (Caffeine during Pregnancy, Iafrica.com).

In the 1983 Ottawa study at Carleton University, Canada, 286 pregnant women were studied. Researchers analyzed the total caffeine intake from all sources. In the first trimester, coffee accounted for 56%, tea 37%, while caffeinated drinks, chocolate bars, chocolate drinks, and caffeinated medications accounted for 7% of the total caffeine intake. 4% of the women consumed 100-300mg. Of coffee, while another 4% consumed more than 300mg. After statistically controlling for other potential factors, the most marked effect for the heavy caffeine users in this study was the reduced birth weight and smaller head circumference. The mean head circumferences of the babies of the heavy users were 1.1cm lesser than the head circumferences of the babies of the group, which used less than 300mg. Of coffee. The former measurements were 33.5 cm. and the latter was 34.6 cm. A decrease of 379gms.in the birth weight of the babies was seen in the heavy-user group. The birth weight reductions are more significant for preterm or small infants where thriving becomes a problem (Watson and Fried, Smaller Head Circumference, Low Birth Weight after 300mg. intake, 1985).

Interesting findings of Dr. Nehligh (Coffee and Caffeine During Pregnancy)ю

Dr. Astrid Nehligh summarized over 200 articles on the subject of coffee/caffeine and presented his findings in the 1994 Journal of Neurotoxicology and Teratology. His assumptions are interesting. He stated that world coffee consumption was increasing.

A mean cup size of caffeinated coffee has about 90mg of caffeine and 65 mg for soluble instant coffee. Decaffeinated coffee only had 3mg. Of caffeine. 150ml. Of tea had 32-42mg.

Cola drinks had 16mg. The daily consumption ranges from 202-283 mg. in males and females between 20 and 75 years.

The half-life of caffeine ranges from 0.7-1.2 hours in rats and mice, 3-5 hours in the monkeys, and 2.5-6 hours in humans. In both humans and animals, during the neonatal period, due to the immaturity of liver enzymes, the half-life of the caffeine is increased. Half-lives of 40-130 hours are recorded from premature and newborn infants. They decrease rapidly to 14.4 hours in 3-5 month infants and 2.6 hours in 5-6 month infants.

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Breastfed infants show a longer half-life than formula-fed.

Comparing results of drug administration, taking metabolic body weight as a correlating factor, he chalked up a few details. 20mg/kg body weight in the rat was found equivalent to 17 cups of coffee (at 100mg/cup) in a 70kg. Man. but only 4-6 cups when corrections are made.

In the monkey, spontaneous abortions and stillbirths have been recorded at two dosage levels. In humans, coffee and caffeine from other sources have caused abortions.

Caffeine or coffee intake has almost no association with prematurity; 11% may be attributed to smoking, 5% to alcohol, and only 2 % to coffee.

Absorption of caffeine has a vasoconstrictive effect on placental circulation.

Blood flow in the fetal vein is not affected, but the intervillous flow becomes less due to caffeine intake. The decreased blood flow with the increased concentration of noradrenaline released due to caffeine in the maternal blood can cause harmful risks to the fetus.

Studies have shown that caffeine accumulates in the brain of the fetus. Caffeine concentration in the fetal rat is found to be higher in the brain than in the placenta.

Some studies indicate that exposure of female rats to caffeine (0.04% in drinking water) in Pregnancy produces a greater loss in brain weight than body weight. This point has been indicated in the study by Tanaka et al. (1987) also.

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When rats absorb 10-20mg/kg day of caffeine, cerebral concentrations are lower at birth. Modifications are seen in the cerebral concentrations of catecholamines, tyrosine, tryptophan, serotonin, 5-hydroxy indole acetic acid, and cyclic nucleotides in the brain of 1-35 day old rats. These result in behavioral abnormalities like hypoactivity during the development period.

Early caffeine exposure, even if in low doses, tend to produce neurochemical changes causing deficits involving the constructive material like the DNA and RNA and the functional material like the neurotransmitters and ions.

Offspring of female rats exposed to 60-100mg/kg caffeine in their drinking water all through gestation have deficits in learning capacities. Their learning capacity is reduced in a new environment. These affected offspring spend less time playing and touching in an open field.

A study by Yakoubi et al. (2000) indicated that the stimulant effect of caffeine on the locomotor function in mice was attributed to the antagonism of the adenosine A1 and A2A receptors.

Caffeine has a biphasic effect. At low doses, stimulation, and at high doses, depression is seen. The results of the study suggested that the stimulant action took place at the receptor A2A and the depressive action at the A1 (Yakoubi et al., 2000).

Research Methodology

Sixty healthy rats of the Sprague-Dawley variety (Holtzman strain, Holtzman Co., Madison) would be selected for the study. Rats are weighing 240-260gms. Would be kept at standard laboratory conditions and fed a standard diet (Ralston Purina Co., St. Louis, MO). The animals would be mated just after being brought to the laboratory. The period of gestation would be counted from the day spermatozoa appear in the vaginal smears.

Twenty pregnant rats would be fed caffeinated coffee instead of drinking water from day one of gestation. Twenty would be fed decaffeinated coffee only. 20 would be the control group to be fed on drinking water only. No other fluids would be provided for these rats.

All would be fed unrestricted quantities of the same diet. The animals would be kept in separate cages. Body weight gain, fluid intake, and food intake would be measured daily.

The caffeinated and decaffeinated coffees would be prepared fresh daily using a Dripolator. The caffeine content of several samples would be determined on different days to recognize the caffeine content in the caffeinated coffee and decaffeinated one.

(Literature has shown that the caffeine content in caffeinated coffee drunk normally is 0.85mg/ml. while decaffeinated coffee has only 0.03mg/ml.)

Delivery of the rats would be watched out for. About 2-3 hours after delivery, their drink would be replaced by normal water. The newborns would be weighed, and each litter would be left with ten pups each. The extra pups would be randomly selected and killed. The brain and liver weights would be recorded. For the first 21 days of lactation, the other pups would not be separated from the dams. All would be feeding on drinking water and no coffee. The litters would not be disturbed. After 21 days, the pups would be separated and caged in groups of 4 animals, two males and two females, until they were 30 days of age. The cages would be placed in the behavioral test room on the 31st day. The animals would be weighed, and behavior in an open field would be observed.

For the two days of the test, they would be in separate cages and fed a standard laboratory diet.


The results are to be derived and presented to complete the thesis. The parameters for achieving the results would be based on the following data: fluid intake, food intake, maternal weight gain, litter size of the pups, neonatal mortality, postnatal mortality, birth weight of pups, a ratio of liver weight to birth weight of the killed ones and ratio of brain weight to body weight. Gross congenital anomalies would be looked out for. The comparisons of the weights of the dams at different stages of their laboratory life would be studied. The behavior of the pups in the open field regarding locomotion, grooming time, and time spent with a novel object (the table) would be studied. Comparison among the three groups would help me draw appropriate conclusions about the effect of caffeine on pregnant rats and their offspring, and hopefully, the results may be interpreted for human beings. I would be using comparison charts derived from my data.


I hope to make appropriate inferences from the comparison between the three groups of pregnant rats. How much and if the caffeine has interfered with the outcome of pregnancies and the behavior of the offspring would be decided towards the end of the study. Whether it was the caffeine or some other factors which caused the outcome would form part of the discussion.


Caffeine During Pregnancy, Web.

Effects on fetuses and newborn children. Web.

Glossier, Daniel S.; “Coffee Consumption During Pregnancy: Subsequent behavioral abnormalities”, Journal of Nutrition, 1982, Vol. 112, Pgs 829-832.

Neligh, Astrid; Coffee and Caffeine during Pregnancy, Journal of Neurotoxicology and Teratology, 1994. Web.

Tanaka H. et al., “ Effects of Maternal Caffeine Ingestion on the perinatal cerebrum”, Biology Neonate, 1987, Vol 51(6), pgs 332-339, Department of Health and Human Studies.

Yakubu, Malika el; “The stimulant effects of caffeine on locomotor behaviour of mice are mediated through its blockade of adenosine A2A receptors”, British Journal of Pharmacology , 2000, Vol 129 , pgs 1465-1473.

Watkinson, B and Fried, P.A.; Smaller Head Circumference, Low Birth Weight after 300mg.intake in “Maternal Caffeine Use Before, During and After Pregnancy and Effects Upon Offspring”, Neurobehavioral Toxicology and Teratology, Vol. 7:9-17.

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