Two rough measures of fetal growth are the duration of pregnancy and the weight of the newborn baby for its gestational age. Once the placenta is fully established, fetal growth and development are dependent on the integrity of the maternal-placental unit and are strongly influenced by maternal stress, workload, metabolic energy and general health.
Introduction
Current research suggests that a woman's ability to meet the needs for fetal development is not related in any simple way to her current or immediate past dietary intake, but rather is more dependent on her general state of health. For example, a mother who becomes pregnant at an early age, before she has completed her own growth, has a limited ability to nourish her fetus.
Shifting the focus: from birth weight to fetal development
Optimal fetal development requires the potential mother to be in a good state of physical and emotional health, both before and during her pregnancy. It therefore follows that factors other than patterns of dietary consumption at conception and during pregnancy determine a mother's ability to nourish her fetus and it is these factors that are the determinants of pregnancy outcomes. Although the concept of low birth weight has been useful as a single criterion for identifying problems of public health concern, it has nevertheless been considered too non-specific and too narrow when used as an indicator of wider aspects of biological function and health. .
For this reason it was agreed that it would be more appropriate to work towards a strategy aimed at optimizing fetal development in the broadest sense of the term. According to this paradigm, birth is viewed as a single event in a continuum of development and change that begins at or before conception and extends into adulthood, and in which prior experience can have effects on subsequent function at all stages of the life cycle. .
Indicators of fetal development
Limitations of birth weight as an indicator of optimal fetal development
Despite its undeniable value as a public health indicator, birth weight does not cover all aspects of fetal growth and development (11). The following apparent paradox highlights some of the problems associated with using birth weight alone as an indicator of improved perinatal health. Thus, in cases where infant mortality rates are declining without concomitant changes in birth weight, use of birth weight alone would fail to detect improvements in perinatal health (12).
The picture is further complicated by the fact that in some situations adverse effects on fetal development are associated with increased birth weight: for example, the infant of a mother who is prediabetic is likely to be larger than normal, but with an increased risk. of poor health (13). In such circumstances, the use of birth weight as the sole indicator of perinatal health may lead to erroneous conclusions.
What constitutes optimal fetal development from a public health perspective?
Although collecting data on a broad spectrum of indicators may not be feasible in all situations, every effort should be made to monitor as broad a set of indicators as possible in sentinel populations in order to demonstrate their value at the level population. Birth weight should be seen as the minimum amount of information that should be collected for all births. In addition, gestational age (maturity) should be measured using early ultrasound (ie at < 20 weeks) in sentinel populations whenever possible.
Where direct measurements are not possible, estimates based on the date of the last menstrual period should be used to indicate the length of pregnancy. If the only measure available is birth weight, residual distributions must be calculated (see Appendix 1).
Effects of sub-optimal fetal development
For many populations, optimal birth weight is greater than average birth weight for many outcomes. For infant mortality, the optimal birth weight may be 350 g more than the average birth weight. This has important policy implications, as it suggests that a small upward shift in the birth weight distribution is likely to have a much larger benefit for the entire population, not just for the relatively few at the extremes of birth weight (22).
For example, if the relationships between cognitive function and birth weight are similar to those between infant mortality and birth weight (ie the optimal birth weight for cognitive function is greater than the mean), then any improvement in birth weight it will bring a significant benefit in terms of better cognitive function in the population, and in turn in terms of reducing poverty.
Causes of sub-optimal fetal development
Nutritional status
Its ability to meet this demand will be determined in part by the extent to which there are other concurrent demands competing for the same resource. Various stresses can also have a negative effect on a woman's nutritional status and ability to maintain a healthy pregnancy. All of the aforementioned risk factors, acting directly or indirectly, have been shown to impair the chance for the fetus to grow and develop normally.
On the other hand are women who are in better health and have a better nutritional status when they conceive. For example, improving the environment, reducing infection risk and reducing workload can all achieve significant improvements in nutritional status for the same dietary intake (28) and should be seen as an integral part of nutrition intervention strategies where appropriate.
Environmental and intergenerational factors
In particular, there is a need to better understand how access to maternal nutrient reserves can be modulated by an adverse environment, thereby leading to constraints on fetal development. For many groups, greatly improved social conditions and access to better diets can thus occur within a single generation, but the biological ability to cope with, and adapt to, the richer environment takes more than a single generation. Upstream” policies are not specified as they are not directly under WHO influence, but will be country/region specific.
Malaria control (i.e. intermittent preventive treatment, insecticide-treated bed nets, case Mx) Access to appropriate healthcare. The “Upstream” policy for all ages is not specified as it is not directly under the influence of WHO but will be country/region specific.
Potential interventions
A life-cycle approach to intervention
The pregnancy outcome is strongly influenced by the mother's age and whether she is fully grown when she becomes pregnant (24). Some data suggest that the growth and development of the fetus is influenced by the nutritional and health status of the mother in the period before she becomes pregnant and her health status at the time of conception. Once the placenta is fully established, fetal development is dependent on the integrity of the maternal-placental unit.
The newborn's health is greatly influenced by its maturity and size, and also by the quality of intrapartum care, the establishment of breastfeeding and the quality of the parents' investment in the infant. The importance of the health of the mother-infant dyad, a concept that extends from conception to well into childhood, was a recurring theme throughout the consultation.
Nutrition as an intervention
Knowledge gaps and priorities for future research
The potential of this approach as a means of identifying a mechanism by which to establish an informative measure of optimal fetal development also warrants further investigation. Therefore, there is an urgent need for advocacy that highlights the functional benefits that can be gained by improving fetal development. The consultation considered that it would be instructive to use the data available to estimate population attributable costs for various fetal development outcomes.
A detailed analysis of how specific health policies have affected programs and outcomes related to optimal fetal development was also proposed as a priority area for future research efforts. It was also recommended that the knowledge base regarding body composition and optimal fetal development be increased, and that the potential to do so be explored using sentinel populations and prospective longitudinal studies of populations, particularly if such studies can be conducted. in transition populations. , and/or in diaspora or migrant populations.
Recommendations
Many of the required components of a strategy to promote optimal fetal development already exist as single packages. Optimal fetal development should be seen as an integral aspect of social development and the achievement of health for all. The Millennium Development Goals (MDGs) provide a timely opportunity to advocate for a strategy to promote optimal fetal development.
A list of interventions – with a description of how each can contribute to achieving optimal fetal development – should also be prepared for policy makers. A major effort should be devoted to monitoring and evaluating ongoing activities aimed at achieving optimal fetal development.
Intrauterine exposure to diabetes mediates risks for type-2 diabetes and obesity: a study of discordant siblings. Dietary protein restriction in pregnant rats induces and folic acid supplementation prevents epigenetic modification of hepatic gene expression in the offspring. Maternal care, gene expression, and the transgenerational transmission of individual differences in stress reactivity.
Effects on birth weight and perinatal mortality of maternal nutritional supplementation in rural Gambia: a 5-year randomized controlled trial. The Washington State Intergenerational Birth Outcomes Study: Methodology and Some Comparisons of Maternal Birth Weight and Infant Birth Weight and Pregnancy in Four Ethnic Groups.
Summaries of the background papers
- Maternal nutrition and low birth weight
- The developmental origins of adult disease
- Paper 3: Optimal fetal growth and size at birth
- Determinants of fetal growth
Perinatal mortality is usually higher at the lower extremes of birth weight and gestational age. Furthermore, the optimal birth weight in the population generally increases as the average birth weight increases. In many populations, the birth weight distribution tends to be toward lower birth weight.
There is no universal reference for birth weight or fetal growth that applies to all fetuses regardless of environment. Although references to birth weight are often referred to as fetal growth curves, they are in fact not the same.
Objectives and expected outcomes
Agenda
To determine current knowledge about what is the optimal size at term from a public health perspective. To review the causes of suboptimal size at term birth and low birth weight as a population-level proxy indicator. To review the effects that suboptimal size at birth has on morbidity, disability and mortality across the life course.
To review (cost-effective) interventions to ensure optimal size in long-term delivery by type of interventions. To advise WHO on the next steps towards the development of the optimal size strategy in long-term birth.
