Hydration in pregnancy and breastfeeding - Guidelines
During pregnancyI. Hydration and the role of water during pregnancyI.1. Changes in body water during pregnancyI.1.1. Total body water increaseI.1.2. Plasma volume expansionI.1.3. Amniotic fluid: ensuring fetal developmentI.1.4. The placenta: the organ for fluid supply to the fetus I.2. Regulation of body water in pregnant womenI.2.1. Water balance in pregnant womenI.2.2. Adaptations to ensure body water balanceI.3. Emerging science regarding water and health outcomes during pregnancyI.3.1. Maternal hydration status: influence on perinatal outcomesI.3.2. ConstipationI.3.3. Urinary tract infections During lactationII. Hydration and the role of water during breastfeedingII.1.Water in breast milkII.2. Consequences of breastfeeding for body waterII.3. Hydration and breast milk productionGuidelinesIII. TESTGuidelines for fluid intake during pregnancy and lactationConclusionReferences
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In contrast to other nutrients, water needs in pregnant and lactating women have attracted little research attention. Theoretically, adequate water intake during pregnancy should match that of a non-pregnant woman, plus the fluid required to support fetal growth, amniotic fluid accretion, and higher blood volume (Montgomery, 2002). During breastfeeding, it should compensate the physiological needs of the mother plus water contained in breast milk.
Several theoretical methods have been used to establish reference values.
In the USA and Canada, adequate water intakes are based on the median total water intake observed in NHANES III data (Third National Health and Nutrition Examination Survey) for pregnant and lactating women, respectively 3000 mL/d and 3800 mL/d (IoM, 2004).
In Australia and New-Zealand, adequate intakes are also based on median water intake. For lactating women, the adequate intake accounts for water lost through breast milk, so that water needs increase by 700 mL/d, compared to non-lactating women.
In Europe, the European Food Safety Authority (EFSA) has set the total water need in pregnant women based on a theoretical calculation. During pregnancy energy intake is estimated to increase by 300 kcal/day. When adjusted to reach an available water amount of 1 mL/kcal ingested, EFSA recommends adding 300 mL/d of water, compared to non-pregnant women of the same age. In lactating women, total water needs should be equivalent to the sum of adequate intake of the non-lactating women plus the water content of the milk produced daily during the first 6 months of lactation, i.e. an addition of 700 mL/d (EFSA, 2010).
Because of these methodological differences, guidelines for total water intake vary greatly among countries (Table 1).
Table 1. Reference values for total water intake in pregnant and lactating women.
Total water intake refers to water from fluid (water and beverages) and the water in food.
Despite large discrepancies in the recommended intake, some conclusions can be drawn by looking at the most recent recommendations. Pregnant women are advised to increase their fluid consumption by at least 300 mL, whereas it seems clear that the needs of lactating women increase by at least 700 mL per day above basic needs (IoM, 2004; NHMRC, 2006; EFSA, 2010). The needs obviously increase far above these figures, in the case of physical activity or living in hot climates (WHO, 2003).
Take home messages
Limited research has been dedicated to determinate the water needs of pregnant and lactating women.
Water intake during pregnancy should equal the adequate intake of a non-pregnant woman, plus the fluid required to support fetal growth, amniotic fluid accretion, and higher blood volume.
In lactating women, total water needs should be equivalent to the sum of the adequate intake of non-lactating women plus the amount of water lost in breast milk, during the first 6 months of lactation.
Despite different guidelines for total water intake among countries, additional amounts of water recommended during pregnancy and lactation are globally consistent, about +300 mL per day in pregnant women and +700 mL per day in breastfeeding women.