Elsevier

The Lancet

Volume 391, Issue 10132, 5–11 May 2018, Pages 1830-1841
The Lancet

Series
Before the beginning: nutrition and lifestyle in the preconception period and its importance for future health

https://doi.org/10.1016/S0140-6736(18)30311-8Get rights and content

Summary

A woman who is healthy at the time of conception is more likely to have a successful pregnancy and a healthy child. We reviewed published evidence and present new data from low-income, middle-income, and high-income countries on the timing and importance of preconception health for subsequent maternal and child health. We describe the extent to which pregnancy is planned, and whether planning is linked to preconception health behaviours. Observational studies show strong links between health before pregnancy and maternal and child health outcomes, with consequences that can extend across generations, but awareness of these links is not widespread. Poor nutrition and obesity are rife among women of reproductive age, and differences between high-income and low-income countries have become less distinct, with typical diets falling far short of nutritional recommendations in both settings and especially among adolescents. Several studies show that micronutrient supplementation starting in pregnancy can correct important maternal nutrient deficiencies, but effects on child health outcomes are disappointing. Other interventions to improve diet during pregnancy have had little effect on maternal and newborn health outcomes. Comparatively few interventions have been made for preconception diet and lifestyle. Improvements in the measurement of pregnancy planning have quantified the degree of pregnancy planning and suggest that it is more common than previously recognised. Planning for pregnancy is associated with a mixed pattern of health behaviours before conception. We propose novel definitions of the preconception period relating to embryo development and actions at individual or population level. A sharper focus on intervention before conception is needed to improve maternal and child health and reduce the growing burden of non-communicable diseases. Alongside continued efforts to reduce smoking, alcohol consumption, and obesity in the population, we call for heightened awareness of preconception health, particularly regarding diet and nutrition. Importantly, health professionals should be alerted to ways of identifying women who are planning a pregnancy.

Introduction

Health of women around the time of conception, once a neglected topic, is now a focus of increasing interest, reflected in several reports from national1, 2 and international health agencies.3, 4 This Series on preconception health makes the case for preconception health as a key determinant of pregnancy success and next generation health, drawing on evidence across clinical, biological, social, and policy fields. In this report, we follow three lines of enquiry. First, we review the evidence linking preconception health, particularly nutritional status, to pregnancy and birth outcomes, including analysis of the few cohort studies to have recruited women before pregnancy in low, middle, and high-income countries (appendix),5, 6, 7, 8 and we survey data on the nutrition of a nationally representative sample of women in a high-income country (the UK).9 Using these data, we assess how well women are prepared, in health terms, for pregnancy. Second, we assess the extent to which intervention during pregnancy can mitigate the effect of preconception risk behaviours by reviewing systematic reviews of dietary and lifestyle interventions that started in pregnancy (appendix). Third, efforts to improve preconception health can be aimed at a population level, irrespective of any pregnancy planning, and can be targeted more specifically at women who are planning for pregnancy. We therefore review what is known about the extent of planning for pregnancy, including new data from a low-income country (Malawi) on how to measure pregnancy planning.10 A host of social, medical, and environmental conditions can influence pregnancy outcomes, including genetic disorders, pre-existing physical and mental health conditions, teratogens, and domestic abuse to name a few. We recognise their importance, but review of these conditions is outside the scope of this paper. The importance of the father's preconception health is addressed in the second Series paper whereas the third Series paper reviews the targeting of intervention strategies to improve preconception health.

Key messages

  • Health before conception is strongly linked to the outcome of pregnancy; life-course research pin-points the preconception period as crucial for health across generations.

  • The preconception period should be redefined according to (1) the biological perspective—days to weeks before embryo development, (2) the individual perspective—a conscious intention to conceive, typically weeks to months before pregnancy occurs, and (3) the public health perspective—longer periods of months or years to address preconception risk factors, such as diet and obesity.

  • Many women of reproductive age in low, middle, and high-income countries will not be prepared nutritionally for pregnancy.

  • Micronutrient supplementation started in pregnancy can correct important maternal nutrient deficiencies, but it is not sufficient to fundamentally improve child health; dietary interventions in pregnancy can limit weight gain, but they are also insufficient in improving pregnancy outcomes.

  • The preconception period presents a period of special opportunity for intervention; the rationale is based on lifecourse epidemiology, developmental (embryo) programming around the time of conception, maternal motivation, and disappointment with interventions starting in pregnancy.

  • Improved measurement shows that pregnancy planning is more common than previously recognised in low, middle, and high-income countries.

  • Identification of people contemplating pregnancy provides a window of opportunity to improve health before conception, while population-level initiatives to reduce the determinants of preconception risks, such as obesity and smoking, irrespective of pregnancy planning, are essential to improve outcomes.

Section snippets

Preconception risk factors in perspective

Life-course epidemiology provides a useful perspective for examination of preconception factors and their effects on maternal, fetal, and child health by consideration of the timing and duration of exposures and their potential long-term or latent effects.11 The relationship of exposures to outcomes can be considered in terms of critical periods, sensitive periods, and cumulative effects. For example, 2–3 months before and after conception is a critical period for optimising gamete function and

Defining the preconception period

The preconception period is often defined as the 3 months before conception, probably because this is the average time to conception for fertile couples.80, 81 However, a time period before conception can only be identified after a woman has become pregnant. Some definitions avoid this problem, for instance “a minimum of one year prior to the initiation of any unprotected sexual intercourse that could possibly result in a pregnancy”,82 but cannot be applied practically.

We therefore propose

Pregnancy planning for preconception health

Compelling evidence for early developmental programming, along with the disappointment from micronutrient supplements and dietary interventions in pregnancy, is shifting attention to the challenge of intervening before conception. Awareness of the importance of health before pregnancy, some level of pregnancy planning, and uptake of interventions before conception are distinct but related requirements for improving preconception health. Qualitative research84 has identified three groups: women

Summary

A consistent picture is emerging of the importance of maternal health before conception and the key risk factors for adverse birth outcomes, one that blurs previous distinctions between low, middle, and high-income countries. A life-course model of critical periods, sensitive periods, and cumulative effects fits well with data linking preconception exposures to birth outcomes and risk of disease in later life. The adverse consequences of poor nutrition combined with obesity, rife in women of

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