Nutrition in Pregnancy and Lactation

Nutrition in pregnancy and lactation concerns the additional and shifted nutrient demands created by carrying and then feeding a child. Pregnancy raises requirements for energy and for several micronutrients to support expansion of maternal tissues and blood volume, the growth of the placenta and fetus, and preparation for lactation; lactation then adds the energy and nutrient cost of milk production. Maternal nutritional status before and during pregnancy is also linked to offspring outcomes.

Definition

Nutrition in pregnancy and lactation is the study of how energy and nutrient requirements change to support gestation and milk production, and of how maternal nutritional status relates to maternal health and to fetal and infant outcomes.

Scope

The topic covers the physiological basis of increased requirements in pregnancy and lactation, key micronutrients of particular importance (such as folate, iron, and iodine), and the relationship between maternal nutrition and pregnancy and offspring outcomes. It is a reference and public-health entry and does not provide individualized prenatal dietary or supplementation prescriptions.

Core questions

• How and why do nutrient requirements change in pregnancy and lactation?
• Which micronutrients are of particular importance before and during pregnancy, and why?
• How does maternal nutritional status relate to fetal growth and offspring health?
• What is the additional nutritional cost of producing breast milk during lactation?

Key concepts

• Increased energy and nutrient requirements
• Periconceptional folate and neural tube defects
• Iron requirements and anaemia in pregnancy
• Iodine and other micronutrients
• Gestational weight gain
• Energy and nutrient cost of lactation
• Maternal nutritional status and fetal growth

Key theories

Developmental origins of health and disease (DOHaD)

The framework holding that the intrauterine and early-life nutritional environment can permanently shape offspring physiology and later disease risk, originating in Barker's work linking fetal and infant conditions to adult disease.

Mechanisms

Pregnancy expands maternal plasma volume and red-cell mass, builds the placenta and fetus, and lays down maternal reserves, increasing requirements for energy and for nutrients including iron, folate, and iodine. Adequate periconceptional folate supports neural tube closure, the basis for the well-established reduction in neural tube defects with folic acid; iron supports the enlarged red-cell mass and fetal needs. During lactation, synthesis of milk imposes an additional energy and nutrient cost. The developmental-origins framework links maternal undernutrition and altered fetal growth with longer-term offspring metabolic risk.

Clinical relevance

Maternal nutrition is a focus of antenatal care because it relates to pregnancy outcomes such as anaemia, fetal growth, and specific birth defects, and to the mother's own reserves during lactation. This entry describes the physiology and population-level evidence; specific supplementation and dietary decisions in pregnancy and lactation should be made with a qualified clinician.

Epidemiology

Iron-deficiency anaemia is common in pregnancy worldwide, and inadequate maternal nutrition contributes to fetal growth restriction and adverse outcomes, especially in low- and middle-income settings, as documented in the Lancet maternal and child nutrition series. Folic acid fortification and supplementation programmes have been associated with reductions in neural tube defects in many populations.

History

The role of maternal diet in pregnancy gained rigorous footing in the twentieth century. A landmark step was the Medical Research Council Vitamin Study (1991), a randomised trial showing that folic acid supplementation prevents neural tube defect recurrence, which underpinned folic-acid policy. In parallel, Barker's work on fetal and infant origins reframed maternal nutrition as a determinant of long-term offspring health, and global syntheses later quantified maternal undernutrition's consequences.

Debates

How broadly should pregnant women be supplemented, and with what?

While folic acid for neural tube defect prevention is well established, the balance of benefits and harms of routine versus targeted iron and of multiple-micronutrient supplements is debated and depends on baseline status and setting, as reviewed in systematic evidence.

Key figures

• David Barker
• Peter Gluckman
• Nicholas Wald
• Robert Black

Seminal works

• mrc-1991
• barker-1990
• gluckman-2008
• black-2013

Frequently asked questions

Why is folic acid emphasised around the time of conception?

Adequate folate during early pregnancy supports closure of the neural tube; a randomised trial and subsequent evidence showed that folic acid supplementation reduces the risk of neural tube defects, which is why it is emphasised periconceptionally rather than later in pregnancy.

Does lactation increase a mother's nutritional needs?

Yes. Producing breast milk has an energy and nutrient cost, so requirements during lactation are higher than at baseline; the magnitude depends on the volume of milk produced and the mother's reserves.