Study: Maternal caffeine intake during pregnancy affects birth, childhood weight

A recent study in BMJ Open shows that mothers exposed to moderate to high levels of caffeine during pregnancy may give birth to infants that gain excess weight in early childhood. The findings from the large observational study reinforce prior recommendations to limit caffeine intake during pregnancy to less than 200 mg per day.

The Norwegian study, which included 50943 mother-child pairs recruited from 2002 to 2008, recorded mothers’ caffeine intake during pregnancy and tracked their children’s growth at 11 age points from 6 weeks to 8 years. At 22 weeks of pregnancy, the expectant mothers were given an adapted 225-question Food Frequency Questionnaire, which included questions about daily caffeine intake and the sources of the caffeine (coffee, black tea, soft drinks, energy drinks, etc.).

The researchers categorized the mothers’ caffeine intake as low (0-49 mg/day), average (50-100 mg/day), high (200-299 mg/day), and very high (> 300 mg/day). The 11 age points at which the children’s weight and length were measured were 6 weeks; 3, 6 and 8 months; and 1, 1.5, 2, 3, 5, 7, and 8 years. Excess infant weight gain was assessed by calculating the difference in gender-adjusted World Health Organization weight-for-age z-scores between birth and 1 year. A z-score > 0.67 represents excess growth.

In the study population, 7.13% (n=3633) and 3.21% (n=1634) of women reported caffeine intake higher than 200 mg/day and 300 mg/day, respectively. The higher the caffeine intake, the higher the likelihood that a mother was older than age 30, multiparous, had a daily energy intake in the upper tertile, smoked during pregnancy, and did not suffer nausea and/or vomiting during pregnancy.

The prevalence of excess growth in infancy also increased from 23% to 29% as prenatal caffeine intake increased from low to very high. After adjusting for confounders, the researchers found that, compared to children born to women who were low consumers of caffeine, those born to women who consumed average, high, and very high amounts of caffeine had progressively higher odds of excess growth: 1.15 (95% CI: 1.09 – 1.22), 1.30 (95% CI: 1.16 – 1.45), and 1.66 (95% CI: 1.42 – 1.93), respectively.

As the participating infants aged, rates of overweight increased by 5% at age 3 years, 6% at age 5 years, and 3% at age 8 years in association with caffeine exposure from low to high to very high, respectively. Children born to average, high, and very high consumers of caffeine had adjusted odds for being overweight at age 3 years of 1.05 (95% CI: 0.99 – 1.12), 1.17 (95% CI: 1.05 – 1.30) and 1.44 (95% CI: 1.24 – 1.67), respectively. Children prenatally exposed to very high rates of caffeine weighed 67 to 83 g more in infancy (age 3-12 months), 110 to 136 g more in toddlerhood (age 1-3 years), 213 to 320 g more at preschool age (3-5 years), and 480 g more at 8 years than did children who were prenatally exposed to low caffeine levels.

The researchers noted that findings from this study reinforce those from previous studies on the associations between prenatal caffeine exposure and birthweight. However, this study also tracked weight gain velocities after birth, following the participating children for 8 years. Some of the strengths of the study were the large number of participants, frequency of the measurements, and assessment of caffeine intake from different sources. Identified weaknesses include the self-reported diet from the mothers and the inability to establish causation because the study was observational.

How does ART affect risk of stillbirth?

A study by researchers from the Centers for Disease Control and Prevention shows that use of assisted reproductive technology (ART) is associated with a reduced risk of stillbirth prior to 28 weeks’ gestation. The findings, based on data from births in Connecticut, Florida, Massachusetts and Michigan, were presented at the 66^th Annual Clinical and Scientific Meeting of the American College of Obstetricians and Gynecologists.

The authors analyzed information from linked ART surveillance and vital records from the four states to examine trends in stillbirth rates and estimated adjusted risk ratios (aRRs) for associations between ART and stillbirth. Adjustments were made for maternal characteristics, pregnancy history, and pre-pregnancy medical conditions. The data also were stratified by plurality and gestational age < 28 and > 28 weeks. ICD-10 codes were used to examine causes of stillbirth.

Outcomes from a total of 15,822 stillbirths between 2006 and 2011 were examined (282 with ART; 15,540 without ART). For both singletons and multifetal pregnancies, rates of stillbirth with ART were lower than when the technology was not used (3.1 versus 6.0 and 9.4 versus 18.3, respectively). At < 28 weeks, the risk of stillbirth among ART pregnancies was significantly lower than for non-ART pregnancies (aRR 0.38, 95% confidence interval [CI] 0.22- 0.65 for singletons and aRR 0.63, 95% CI 0.42-0.94 for multiples).

For ART and non-ART pregnancies, leading causes of stillbirth were similar: maternal conditions such as hypertension, infection, respiratory disease, periodontal disease. incompetent cervix (16.6%); and fetal issues such as placental abnormalities (9.8%); umbilical cord conditions (9.2%); chorioamnionitis (3.8%); and low birth weight (2.7%).

The authors believe that in the ART group, the lower rates of stillbirth seen at < 28 weeks may be because of earlier detection and management of fetal and maternal conditions. Slower calorie burn for obese black mothers during pregnancy

A study published in The FASEB Journal found that obese African-American women have significantly lower energy expenditure  per kilogram of mass compared to obese white women with similar energy intake and physical activity levels. The researchers believe the findings illustrate a need for updated weight gain recommendations for obese women with a more individualized focus.

In the study, 34 black and 32 white women (n=66) with obesity were included. The women had a similar body mass index (BMI) (36.9±0.7 kg/m_­²), body fat percentage (55.1±1.1 kg, P = 0.009) and age (27.7±0.6 years). A BMI of 30 or above at the start of pregnancy is considered obese. Metabolic and behavioral phenotyping for the study took place between 14 and 16 weeks’ gestation. Energy expenditure was measured in free-living conditions over 1 week using stable isotopes and a room calorimeter during sleep. Body composition was measured using air displacement plethysmography. Physical activity was measured using accelerometers.

The researchers found that the African-American participants had more fat-free mass than the white participants (56.9±1.6 vs 51.6±1.1 kg, P = 0.06). In addition, total daily energy intake was significantly lower in the African-American participants than in the white participants (2633±88 vs 2901±76 kcal/d, P = 0.03). Initial results showed that food intake and total daily energy expenditure (TDEE) were not different between the two groups (2590±77 vs 2711±56 kcal/d, P = 0.21). But after correction for individual differences in body composition, the researchers found that TDEE was significantly lower in African-American women (-231±74 kcal/d, P = 0.003). African-American women also had lower energy expenditure during sleep after adjusting for body composition (-81±37 kcal/d, P = 0.03).  Daily activity levels and composition of diet in the two groups were similar.

The researchers believe their findings could have an impact on the current non-race-specific caloric intake guidelines for pregnant women, specifically for energy intake during pregnancy.  Because the findings show that African-American mothers expend a lower amount of energy, the current guidelines may lead to unintentional overeating and contribute to the increasing prevalence of excessive gestational weight gain in this population.