Effect of reducing caffeine intake on birth weight and length of gestation: randomised controlled trial

Methylxanthines during pregnancy and early postnatal life

World-wide, many fetuses and infants are exposed to methylxanthines via maternal consumption of coffee and other beverages containing these substances. Methylxanthines (caffeine, theophylline and aminophylline) are also commonly used as a medication for apnea of prematurity.The metabolism of methylxanthines is impaired in pregnant women, fetuses and neonates, leading to accumulating levels thereof. Methylxanthines readily passes the placenta barrier and enters all tissues and thus may affect the fetus/newborn at any time during pregnancy or postnatal life, given that the effector systems are mature.At clinically relevant doses, the major effector system for methylxanthines is adenosine receptors. Animal studies suggest that adenosine receptors in the cardiovascular, respiratory and immune system are developed at birth, but that cerebral adenosine receptors are not fully functional. Furthermore animal studies have shown protective positive effects of methylxanthines in situations of hypoxia/ischemia in neonates. Similarly, a positive long-term effect on lung function and CNS development was found in human preterm infants treated with high doses of caffeine for apneas. There is now evidence that the overall benefits from methylxanthine therapy for apnea of prematurity outweigh potential short-term risks.On the other hand it is important to note that experimental studies have indicated that long-term effects of caffeine during pregnancy and postnatally may include altered behavior and altered respiratory control in the offspring, although there is currently no human data to support this.Some epidemiology studies have reported negative effects on pregnancy and perinatal outcomes related to maternal ingestion of high doses of caffeine, but the results are inconclusive. The evidence base for adverse effects of caffeine in first third of pregnancy are stronger than for later parts of pregnancy and there is currently insufficient evidence to advise women to restrict caffeine intake after the first trimester.

Caffeine consumption during pregnancy and risk of preterm birth: a meta-analysis

BACKGROUND

The effect of caffeine intake during pregnancy on the risk of preterm delivery has been studied for the past 3 decades with inconsistent results.

OBJECTIVE

We performed a meta-analysis examining the association between caffeine consumption during pregnancy and risk of preterm birth.

DESIGN

We searched MEDLINE and EMBASE articles published between 1966 and July 2010, cross-referenced reference lists of the retrieved articles, and identified 15 cohort and 7 case-control studies that met inclusion criteria for this meta-analysis.

RESULTS

The combined odds ratios (ORs) obtained by using fixed-effects models for cohort studies were 1.11 (95% CI: 0.96, 1.28), 1.10 (95% CI: 1.01, 1.19), and 1.08 (95% CI: 0.93, 1.27) for risk of preterm birth comparing the highest with the lowest level of caffeine intake (or no intake) (mg/d) during the first, second, and third trimesters, respectively. Results for the case-control studies yielded no associations for the first (OR: 1.07; 95% CI: 0.84, 1.37), second (OR: 1.17; 95% CI: 0.94, 1.45), or third (OR: 0.94; 95% CI: 0.79, 1.12) trimesters. No overall heterogeneity was found by region, publication decade, exposure and outcome assessment, caffeine sources, or adjustment for confounding, which was largely driven by individual studies.

CONCLUSION

In this meta-analysis, we observed no important association between caffeine intake during pregnancy and the risk of preterm birth for cohort and case-control studies.

A review of the epidemiologic evidence concerning the reproductive health effects of caffeine consumption: a 2000-2009 update

This review of human studies of caffeine and reproductive health published between January 2000 and December 2009 serves to update the comprehensive review published by Leviton and Cowan (2002). The adverse reproductive outcomes addressed in this review include: (1) measures of subfecundity; (2) spontaneous abortion; (3) fetal death; (4) preterm birth; (5) congenital malformations; and (6) fetal growth restriction. Methodologic challenges and considerations relevant to investigations of each reproductive endpoint are summarized, followed by a brief critical review of each study. The evidence for an effect of caffeine on reproductive health and fetal development is limited by the inability to rule out plausible alternative explanations for the observed associations, namely confounding by pregnancy symptoms and smoking, and by exposure measurement error. Because of these limitations, the weight of evidence does not support a positive relationship between caffeine consumption and adverse reproductive or perinatal outcomes.

Maternal caffeine intake from coffee and tea, fetal growth, and the risks of adverse birth outcomes: the Generation R Study

BACKGROUND

Caffeine is a widely used and accepted pharmacologically active substance. The effect of caffeine intake during pregnancy on fetal growth and development is still unclear.

OBJECTIVE

We examined the associations of maternal caffeine intake, on the basis of coffee and tea consumption, with fetal growth characteristics measured in each trimester of pregnancy and the risks of adverse birth outcomes.

DESIGN

Associations were studied in 7346 pregnant women participating in a population-based prospective cohort study from early pregnancy onward in the Netherlands (2001-2005). Caffeine intake in the first, second, and third trimesters was on the basis of coffee and tea consumption and was assessed by questionnaires. Fetal growth characteristics were repeatedly measured by ultrasound. Information about birth outcomes was obtained from hospital records.

RESULTS

We observed no consistent associations of caffeine intake with fetal head circumference or estimated fetal weight in any trimester. Higher caffeine intake was associated with smaller first-trimester crown-rump length, second- and third-trimester femur length, and birth length (P for trend <0.05). Offspring of mothers who consumed > or =6 caffeine units/d tended to have increased risks of small-for-gestational-age infants at birth.

CONCLUSIONS

Our results suggest that caffeine intake of > or =6 units/d during pregnancy is associated with impaired fetal length growth. Caffeine exposure might preferentially adversely affect fetal skeletal growth. Further studies are needed to assess these associations in non-European populations and to assess the postnatal consequences.

Caffeine levels in beverages from Argentina's market: application to caffeine dietary intake assessment

The caffeine content of different beverages from Argentina's market was measured. Several brands of coffees, teas, mates, chocolate milks, soft and energy drinks were analysed by high-performance liquid chromatography (HPLC) with ultraviolet detection. The highest concentration level was found in short coffee (1.38 mg ml(-1)) and the highest amount per serving was found in instant coffee (95 mg per serving). A consumption study was also carried out among 471 people from 2 to 93 years of age to evaluate caffeine total dietary intake by age and to identify the sources of caffeine intake. The mean caffeine intake among adults was 288 mg day(-1) and mate was the main contributor to that intake. The mean caffeine intake among children of 10 years of age and under was 35 mg day(-1) and soft drinks were the major contributors to that intake. Children between 11 and 15 years old and teenagers (between 16 and 20 years) had caffeine mean intakes of 120 and 240 mg day(-1), respectively, and mate was the major contributor to those intakes. Drinking mate is a deep-rooted habit among Argentine people and it might be the reason for their elevated caffeine mean daily intake.

Caffeine intake during pregnancy, late miscarriage and stillbirth

Caffeine is a commonly consumed drug during pregnancy with the potential to affect the developing fetus. Findings from previous studies have shown inconsistent results. We recruited a cohort of 2,643 pregnant women, aged 18-45 years, attending two UK maternity units between 8 and 12 weeks gestation from September 2003 to June 2006. We used a validated tool to assess caffeine intake at different stages of pregnancy and related this to late miscarriage and stillbirth, adjusting for confounders, including salivary cotinine as a biomarker of smoking status. There was a strong association between caffeine intake in the first trimester and subsequent late miscarriage and stillbirth, adjusting for confounders. Women whose pregnancies resulted in late miscarriage or stillbirth had higher caffeine intakes (geometric mean = 145 mg/day; 95% CI: 85-249) than those with live births (103 mg/day; 95% CI: 98-108). Compared to those consuming < 100 mg/day, odds ratios increased to 2.2 (95% CI: 0.7-7.1) for 100-199 mg/day, 1.7 (0.4-7.1) for 200-299 mg/day, and 5.1 (1.6-16.4) for 300+ mg/day (P (trend) = 0.004). Greater caffeine intake is associated with increases in late miscarriage and stillbirth. Despite remaining uncertainty in the strength of association, our study strengthens the observational evidence base on which current guidance is founded.

Peripartum implications of caffeine intake in pregnancy: is there cause for concern?

Maternal use of "social drugs" such as caffeine, ethanol and tobacco in pregnancy is on increase- -worldwide. Caffeine is probably the most frequently ingested pharmacologically active substance in the world. It is found in common beverages (coffee, tea, soft drinks), in products containing cocoa or chocolate, and in medications. Because of its wide consumption at different levels by most segments of the population, the public and the scientific community have expressed interest in the potential for caffeine to produce adverse effects on human health. Reproductive-aged and pregnant women are 'at risk' subgroups of the population who may require specific advice on moderating their daily caffeine intake. This article highlights the implications of caffeine intake in pregnancy, reviews the latest evidence-based information available on this subject, and offers recommendations (practical advice) for anesthesiologists and obstetrician-gynecologists proving peripartum care to these potentially complicated pregnancies.

A substantial and confusing variation exists in handling of baseline covariates in randomized controlled trials: a review of trials published in leading medical journals

OBJECTIVE

Statisticians have criticized the use of significance testing to compare the distribution of baseline covariates between treatment groups in randomized controlled trials (RCTs). Furthermore, some have advocated for the use of regression adjustment to estimate the effect of treatment after adjusting for potential imbalances in prognostically important baseline covariates between treatment groups.

STUDY DESIGN AND SETTING

We examined 114 RCTs published in the New England Journal of Medicine, the Journal of the American Medical Association, The Lancet, and the British Medical Journal between January 1, 2007 and June 30, 2007.

RESULTS

Significance testing was used to compare baseline characteristics between treatment arms in 38% of the studies. The practice was very rare in British journals and more common in the U.S. journals. In 29% of the studies, the primary outcome was continuous, whereas in 65% of the studies, the primary outcome was either dichotomous or time-to-event in nature. Adjustment for baseline covariates was reported when estimating the treatment effect in 34% of the studies.

CONCLUSIONS

Our findings suggest the need for greater editorial consistency across journals in the reporting of RCTs. Furthermore, there is a need for greater debate about the relative merits of unadjusted vs. adjusted estimates of treatment effect.

Antenatal environmental stress and maturation of the breathing control, experimental data

The nervous respiratory system undergoes postnatal maturation and yet still must be functional at birth. Any antenatal suboptimal environment could upset either its building prenatally and/or its maturation after birth. Here, we would like to briefly summarize some of the major stresses leading to clinical postnatal respiratory dysfunction that can occur during pregnancy, we then relate them to experimental models that have been developed in order to better understand the underlying mechanisms implicated in the respiratory dysfunctions observed in neonatal care units. Four sections are aimed to review our current knowledge based on experimental data. The first will deal with the metabolic factors such as oxygen and glucose, the second with consumption of psychotropic substances (nicotine, cocaine, alcohol, morphine, cannabis and caffeine), the third with psychoactive molecules commonly consumed by pregnant women within a therapeutic context and/or delivered to premature neonates in critical care units (benzodiazepine, caffeine). In the fourth section, we take into account care protocols involving extended maternal-infant separation due to isolation in incubators. The effects of this stress potentially adds to those previously described.

Effects of restricted caffeine intake by mother on fetal, neonatal and pregnancy outcome

BACKGROUND

Maternal caffeine consumption during pregnancy may have adverse effects on fetal, neonatal and maternal outcomes.

OBJECTIVES

This review investigates the effects of restricting caffeine intake by mothers on fetal, neonatal and pregnancy outcomes.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (December 2008), scanned bibliographies of published studies and corresponded with investigators.

SELECTION CRITERIA

Randomised controlled trials including quasi-randomised controlled trials (RCTs) investigating the effect of caffeine and/or supplementary caffeine versus restricted caffeine intake or placebo on pregnancy outcome.

DATA COLLECTION AND ANALYSIS

The two review authors independently assessed trial quality and extracted data.

MAIN RESULTS

One study met the inclusion criteria. Caffeinated instant coffee (568 women) was compared with decaffeinated instant coffee (629 women) and it was found that reducing the caffeine intake of regular coffee drinkers (3+ cups/day) during the second and third trimester by an average of 182 mg/day did not affect birthweight or length of gestation.

AUTHORS' CONCLUSIONS

There is insufficient evidence to confirm or refute the effectiveness of caffeine avoidance on birthweight or other pregnancy outcomes. There is a need to conduct high-quality, double-blinded RCTs to determine whether caffeine has any effect on pregnancy outcome.

Caffeine in pregnancy

Caffeine is probably the most frequently ingested pharmacologically active substance in the world. It is found in common beverages (coffee, tea, soft drinks), in products containing cocoa or chocolate, and in medications. Because of its wide consumption at different levels by most segments of the population, the public and the scientific community have expressed interest in the potential for caffeine to produce adverse effects on human health. Reproductive-aged and pregnant women are 'at risk' subgroups of the population who may require specific advice on moderating their daily caffeine intake. This article highlights the implications of caffeine intake in pregnancy, reviews the latest evidence-based information available on this subject, and offers recommendations (practical advice) for the obstetrician-gynecologists proving peripartum care to these potentially complicated pregnancies.

Smoking cessation early in pregnancy and birth weight, length, head circumference, and endothelial nitric oxide synthase activity in umbilical and chorionic vessels: an observational study of healthy singleton pregnancies

BACKGROUND

Reduced production of the vasodilator nitric oxide (NO) in fetal vessels in pregnant smokers may lower the blood flow to the fetus and result in lower birth weight, length, and head circumference. The present study measured endothelial NO synthase (eNOS) activity in fetal umbilical and chorionic vessels from nonsmokers, smokers, and ex-smokers and related the findings to the fetal outcome.

METHODS AND RESULTS

Of 266 healthy, singleton pregnancies, 182 women were nonsmokers, 43 were smokers, and 41 stopped smoking early in pregnancy. eNOS activity and concentration were quantified in endothelial cells of the fetal vessels. Cotinine, lipid profiles, estradiol, l-arginine, and dimethylarginines that may affect NO production were determined in maternal and fetal blood. Serum cotinine verified self-reported smoking. Newborns of smokers had a lower weight (P< or =0.001) and a smaller head circumference (P< or =0.041) and were shorter (P< or =0.001) than newborns of nonsmokers and ex-smokers. eNOS activity in umbilical veins of smokers was 36% lower (P<0.001), eNOS concentration was 47% lower (P<0.001), and the fetal plasma level of high-density lipoprotein was 18% lower (P<0.001) than those of nonsmokers, whereas the same levels were found in umbilical veins from ex-smokers and nonsmokers. The same patterns in eNOS activity and concentration were found in umbilical arteries and chorionic vessels. Fetal plasma levels of estradiol, l-arginine, dimethylarginines, total cholesterol, and triglycerides were similar for nonsmokers, smokers, and ex-smokers.

CONCLUSIONS

The findings suggest that maternal smoking reduces eNOS activity in the fetal vascular bed, contributing to retarded fetal growth caused by the reduction of vasodilatory capacity, and suggest that smoking cessation early in pregnancy prevents these effects in newborns.

Coffee consumption during pregnancy and the risk of hyperkinetic disorder and ADHD: a prospective cohort study

AIM

Based on hypotheses from experimental studies, we studied the association between intrauterine exposure to coffee and the risk of clinically verified hyperkinetic disorder and attention-deficit hyperactivity disorder (ADHD).

METHODS

A cohort study with prospectively collected data from the Aarhus Birth Cohort, Denmark. We included 24 068 singletons delivered between 1990 and 1998. Linkage was performed with three Danish longitudinal registers: The Danish Psychiatric Central Register, The Integrated Database for Labour Market Research and The Danish Civil Registration System. We identified 88 children with hyperkinetic disorder and ADHD. Information about coffee consumption during pregnancy was obtained at 16 weeks of gestation from self-administrated questionnaires. Potential confounding factors were evaluated using Cox regression analyses.

RESULTS

We found that intrauterine exposure to 10 or more cups of coffee per day was associated with a threefold increased risk of hyperkinetic disorder and ADHD. After adjustments for a number of confounding factors, the risk decreased and became statistically insignificant (RR 2.3, 95% CI 0.9-5.9).

CONCLUSION

Prenatal exposure to high levels of coffee did not significantly increase the risk of clinically verified hyperkinetic disorder and ADHD in childhood.

Optimizing natural fertility

This Committee Opinion provides practitioners with suggestions for optimizing the likelihood of achieving pregnancy in couples attempting conception who have no evidence of infertility.

Maternal caffeine intake during pregnancy and risk of fetal growth restriction: a large prospective observational study

OBJECTIVE

To examine the association of maternal caffeine intake with fetal growth restriction.

DESIGN

Prospective longitudinal observational study.

SETTING

Two large UK hospital maternity units.

PARTICIPANTS

2635 low risk pregnant women recruited between 8-12 weeks of pregnancy. Investigations Quantification of total caffeine intake from 4 weeks before conception and throughout pregnancy was undertaken with a validated caffeine assessment tool. Caffeine half life (proxy for clearance) was determined by measuring caffeine in saliva after a caffeine challenge. Smoking and alcohol were assessed by self reported status and by measuring salivary cotinine concentrations.

MAIN OUTCOME MEASURES

Fetal growth restriction, as defined by customised birth weight centile, adjusted for alcohol intake and salivary cotinine concentrations.

RESULTS

Caffeine consumption throughout pregnancy was associated with an increased risk of fetal growth restriction (odds ratios 1.2 (95% CI 0.9 to 1.6) for 100-199 mg/day, 1.5 (1.1 to 2.1) for 200-299 mg/day, and 1.4 (1.0 to 2.0) for >300 mg/day compared with <100 mg/day; test for trend P<0.001). Mean caffeine consumption decreased in the first trimester and increased in the third. The association between caffeine and fetal growth restriction was stronger in women with a faster compared to a slower caffeine clearance (test for interaction, P=0.06).

CONCLUSIONS

Caffeine consumption during pregnancy was associated with an increased risk of fetal growth restriction and this association continued throughout pregnancy. Sensible advice would be to reduce caffeine intake before conception and throughout pregnancy.

Position of the American Dietetic Association: nutrition and lifestyle for a healthy pregnancy outcome

It is the position of the American Dietetic Association that women of child-bearing ages should maintain good nutritional status through a lifestyle that optimizes maternal health and reduces the risk of birth defects, suboptimal fetal growth and development, and chronic health problems in their children. The key components of a health-promoting lifestyle during pregnancy include appropriate weight gain; appropriate physical activity; consumption of a variety of foods in accordance with the Dietary Guidelines for Americans 2005; appropriate and timely vitamin and mineral supplementation; avoidance of alcohol, tobacco, and other harmful substances; and safe food handling. Pregnant women with inappropriate weight gain, hyperemesis, poor dietary patterns, phenylketonuria, certain chronic health problems, or a history of substance abuse should be referred to a registered dietitian for medical nutrition therapy. Prenatal weight gain within the Institute of Medicine recommended ranges has been associated with better pregnancy outcomes. Most pregnant women need 2,200 to 2,900 kcal a day, but prepregnancy body mass index, rate of weight gain, maternal age, and appetite must be considered when tailoring this recommendation to the individual. The consumption of more food to meet energy needs, and the increased absorption and efficiency of nutrient utilization that occurs in pregnancy, are generally adequate to meet the needs for most nutrients. However, vitamin and mineral supplementation is appropriate for some nutrients and situations. This position paper also includes recommendations pertaining to use of alcohol, tobacco, caffeine, and illicit drugs.

Dietary effects on fertility treatment and pregnancy outcomes

PURPOSE OF REVIEW

We summarize the dietary modifications that optimize fertility treatment outcomes.

RECENT FINDINGS

Body weight and nutritional status are closely related to reproductive function. However, few studies have investigated the direct effects of dietary modification on fertility treatment outcomes. Research on nutrition in pregnancy suggests that reduction in glycemic load and micronutrient supplementation may improve pregnancy outcomes.

SUMMARY

Body weight and specific dietary factors may affect fertility but evidence regarding dietary effects on fertility treatment outcomes is lacking. Research suggests that diets with a low glycemic load during pregnancy may reduce the risk of gestational diabetes or large-for-gestational-age births after adjusting for body mass index and total energy intake, but the effect of protein modification remains controversial. There is also lack of information on the impact of energy restriction during pregnancy on maternal and infant outcomes. Folate supplementation is recommended for prevention of birth defects but further research is required to determine the optimal dose to reduce the risks of multiple gestations. Further information on the upper limits of caffeine and alcohol intake during pregnancy would also be useful.

Parental characteristics as predictors of birthweight

BACKGROUND

Previous studies provided conflicting results on the relevance of parental characteristics for offspring's size at birth. The objective of this study was to investigate parental predictors of birthweight.

METHODS

In this cross-sectional study, 34,063 women in the Nurses' Mother's Cohort were queried about parental characteristics during the pregnancy with and birthweight of their nurse daughter.

RESULTS

The predictive linear regression model of birthweight included 13 factors and the majority of the predictive power came from parental anthropometric factors. In the adjusted analysis, daily consumption of each additional glass of milk was associated with an increase of approximately 6 g in birthweight (P for trend = 0.01) and daily consumption of each additional cup of coffee was associated with a decrease of approximately 10 g in birthweight (P for trend < 0.0001). Drinking 1-2, 3-4 and 5+ cups of coffee daily was associated with a 28% [95% confidence interval (CI) 0.12, 0.47], 30% (95% CI 0.10, 0.55) and 63% (95% CI 0.25, 1.12) increase, respectively, in the odds of intrauterine growth restriction when compared with non-drinkers.

CONCLUSIONS

The present study confirmed several previously reported determinants of birthweight. Maternal dietary intake of milk and coffee during pregnancy may influence fetal growth.

Subgroup analyses: how to avoid being misled

Three simple examples from recent BMJ papers illustrate how to understand subgroup analyses and why they may be misleading

Coffee and pregnancy

A moderate reduction in caffeine intake in the second half of pregnancy has no effect on birth weight or length of gestation