Amsterdam Born Children and their Development
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Results

The ABCD study aims to investigate and determine risk factors in early life (during pregnancy and infancy) that might explain later health and development of the child. Although ethnicity is known to be an important determinant of differences in health and development in children, it remains unclear by which mechanisms these differences are mediated. For this reason, the ABCD study is designed to examine and explain health inequalities in children from different ethnic groups. For an outline of the main research areas within the ABCD study follow this link. In the next paragraphs you will find a short overview of results that were published in international peer reviewed scientific journals. A complete list of publications can be found here.

Nutrition

An important area of research within the ABCD project focuses on ‘nutrition’. This term encompasses primarily the maternal nutritional status in pregnancy, i.e. her blood levels of vitamins, minerals and omega-3 and omega-6 fatty acids.

Nutrition and birth outcomes
Our research shows that low folic acid intake, low vitamin D levels and an unfavourable fatty acid profile (relatively high levels of omega-6 fatty acids and low levels of omega-3 fatty acids) increase the risk of delivering an infant with a low birth weight. Non-Dutch ethnic women more often show an adverse nutrient status: a more unfavourable fatty acid profile, lower vitamin D status en lower folic acid intake. These differences explain ethnic differences in birth outcomes to a small extent.

Nutrition and infant health
Examining maternal nutritional status in pregnancy in relation to offspring health in infancy, provides insight in the potential long-term effects. A low maternal vitamin D status was associated with accelerated growth in infancy. Of course, a baby should grow adequately. However, evidence suggests that growing too fast (accelerated growth) increases the risk of later cardiovascular disease. Mothers who had low vitamin B12 levels in pregnancy more often gave birth to an excessively crying infant. This could be the result of the maternal vitamin B12 status affecting the development of the sleep-wake rhythm which in turn affects crying behaviour.

Nutrition and maternal health
Naturally, the maternal nutritional status will affect maternal health as well. Within the ABCD study we have investigated the relation between maternal vitamin D status and depressive symptoms. Vitamin D has many physiologic functions in the human body, including functions in the brain and consequently mental health. Our research showed that mothers with low vitamin D status more often report depressive symptoms than mothers with normal vitamin D levels. Whether an increase in vitamin D intake can effectively diminish or prevent depressive symptoms remains to be established in future research.

Ethnic disparities in health

The ABCD study investigates disparities between ethnic groups in the Netherlands. For example, we have examined ethnic disparities in maternal lifestyle during pregnancy, in birth outcomes, and in child growth and health.

Pregnancy and birth outcomes
So far, results have shown that women of Surinamese, Antillean and Ghanaian ethnic background more often give birth to a premature infant or an infant with low birth weight. We also observed ethnic differences in the timing of prenatal care, the use of folic acid supplements and in thyroid functioning. The ethnic disparities in birth outcomes were partly explained by these differences, but other well known risk factors, such as smoking, are also relevant. Obesity before pregnancy leads to an increased risk for preterm birth as well as large for gestational age babies. This increased risk applies to all pregnant women, however, the prevalence of obesity is much higher in non-Dutch women which makes the contribution of this problem to adverse pregnancy outcomes in this group much larger. Other results show that there is a strong association between obesity and maternal lipid levels (e.g. cholesterol), this association is different between ethnic groups. Ghanaian pregnant women have a favourable profile despite their excessive weight, while Moroccan pregnant women show unfavourable profiles already with small increase in adiposity.

Ethnic differences child growth and health
Ethnic differences in overweight are already seen in very young children at the age of 2-3 years. The percentage of Turkish and Moroccan children that are overweight is 2-3 times higher compared to children of ethnic Dutch origin. Important factors that partially explain these differences are maternal pre-pregnancy BMI and the infant’s weight gain in the first 6 months of life.
We found ethnic differences in infant feeding patterns, Turkish mothers breastfed more often and with a longer duration compared to Dutch mothers and Moroccan mothers introduced bottle feeding earlier which resulted in a longer period of mixed feeding as opposed to exclusive breastfeeding. Children from African origin were breastfed for a shorter period and had an earlier introduction of formula and complementary feeding. In contrast to our expectations, growth in the first 6 months of life was not explained by differences in these feeding patterns during infancy. Overall, we found that breastfeeding, irrespective of ethnicity, results in slower gain in weight and length during the first 6 months of life in all ethnic groups.
Our results show that mothers frequently underestimate the actual weight status of their child, especially mothers from Turkish or Moroccan ethnic origin. Maternal level of education and culture are found to be important determinants in explaining these differences. These findings emphasize that recognition of overweight in children by their parents is of critical importance in the early identification of childhood overweight. If overweight is recognized early in life, prevention and treatment strategies are more likely to be successful.

Psychosocial stress

Psychosocial stress and negative emotions during pregnancy are known to be important risk factors for the physical health and neurobehavioural development of the foetus and child in later life. Hence, these determinants are studied extensively within the ABCD study.

Physical health
Maternal depressive symptoms during pregnancy were associated with a shorter pregnancy duration and related lower birth weight. The combination of depressive symptoms and low folate (vitamin B9) in the blood (present in 7.6% of the pregnant women) was associated with a shorter pregnancy duration of 2.8 days on average. Depression and low vitamin intake often go hand in hand, but the effects they have on birth outcomes are independent of one another.
Job strain (also known as work stress) during pregnancy, was not associated with more overweight/obesity or fat mass in the child at age five-six. It also appears that multiple forms of psychosocial stress in the mother during pregnancy are not associated with measures of the child’s autonomic nervous system (e.g. a decreased variation in heart frequency, a known risk factor for ischaemic disease in later life) in 5-6 year olds at rest. Results show that workstress, a combination of high work load with low control leads to lower birth weight. Pregnant women who reported high work stress in combination with a long workweek have a two times higher risk for giving birth to a small for gestational age child.

Cognition and behaviour
Five to six year old children of mothers who felt very anxious during their pregnancy performed less well on a response speed task, especially when this task became more complex, and required inhibitory control. Boys of women who were highly anxious during pregnancy also showed impairments in performance in simple task conditions. In addition, we found that elevated levels of anxiety during pregnancy were related to behaviour problems in their children. Children of highly anxious mothers were more often hyperactive and had problems to focus or keep their attention, showed more emotional problems and peer relationship problems. Furthermore, boys of women who were highly anxious during pregnancy showed more hyperactivity/inattention problems and overall problem behaviour compared to girls.

Growth
Earlier studies have shown that faster growth in infants possibly can lead to overweight and cardiovascular disease in later life. Infants of women with a high blood pressure during pregnancy more frequently have growth acceleration in weight. We would advice to monitor the growth of these children attentively after birth.