10/18/2002

• Carbohydrate• Protein• Lipids• Vitamins and Minerals:

– General– Vitamins– Iron– Zinc– Calcium– Magnesium

What evidence-based medicine is:

The practice of EBM requires the integration of

• individual clinical expertise

with the

• best available external clinical evidence from systematic research.

Three solutions

Clinical performance can keep up to date:1 by learning how to practice evidence-

based medicine ourselves.2 by seeking and applying evidence-based

medical summaries generated by others.3 by accepting evidence-based practice

protocols developed by our colleagues.

The Five Strengths of Evidence Strong Evidence from at least one systematic

review of multiple well-designed RCT Strong evidence of at least one well designed

RCT of appropriate size Evidence from well designed trials without

randomization, single group pre-post, cohort, time series or matched case control

Evidence from well designed non-experimental studies from more than one research group

Opinions of respected authorities based on clinical evidence, descriptive studies or reports of expert committees

2002 DRI for Carbohydrate

• In general all DRIs for carbohydrate based on brain glucose utilization.

• DRI for adults and children = 130 g/day

• Median intake ~:– Men: 200-330 g/day– Women: 180-230 g/day

2002 DRI for Carbohydrate in Pregnancy

• Fetal brain needs a minimum of 33 g/day• EAR for pregnancy (all ages) = 135 g/day• RDA for pregnancy (all ages) = 175 g/day

– CV is 15% based on variations in brain glucose utilization

– RDA = EAR plus twice CV

EAR: Estimated Average Requirement

CV: coefficient of variation (used when insufficient data to determine standard deviation)

2002 DRI for Fiber in Pregnancy

• “There is no evidence to suggest the beneficial effects of fiber in reducing risk of CHD is different from non-pregnant adolescent girls and women.”

• AI=28 g/day (14 g/1,000 kcal x median kcal intake for group)

• AI for non-pregnant women is 25 g/day

Protein - old RDAs

• 1980: an additional 30 g for pregnancy

• 1989:– Protein RDA is 0.8 per kg for non-pregnant

woman– Additional 10 g for pregnancy

Protein - 1989 RDA

Category G proteinFemale 15-18 44Female 19-24 46Female 25-50 50Pregnant 60Lactating first 6 mos. 65Lactating second 6 mos. 62

2002 RDA

EAR for Protein in Pregnancy

• EAR = 21 g/day above protein needs at prepregnancy weight

• EAR Per kg– Increased amount on a per kg basis is 0.22

g/protein/kg/day– EAR for non-pregnant = 0.66 g protein/kg

per day– EAR per kg=0.88 g/kg/day

RDA for Protein for Pregnancy

• 1.1 g/kg/day or 25 g/day additional protein

• RDA for women aged 19-50 is 0.80 or 46 g/day

• RDA is 71g protein per day

Reference woman is 57 kg

RDA to Diet

• RDAs calculated using high quality reference proteins like egg, meat, milk or fish

• However, even with adjustments for lower quality proteins most women in the US who are meeting energy needs with reasonable food choices, will meet protein needs.

Vegan Diet & Protein Intake

Food Gprotein

#servings

Total gprotein

Totalkcal

Grains 3 11 33 880

Vegetables 4 2 8 100

Beans 15 2 cups 30 550

Total 71 1450

Protein Intakes

• Range in US is 75 to 110 g per day for women

Energy and Protein

• If energy needs are not met by diet then protein will be used for energy

• RDA calculations assume adequate energy intake

Protein Supplementation

• In developing countries protein and energy supplements may improve pregnancy outcomes when women are undernourished

• There is little evidence that protein supplementation affects outcome in developed countries

Adverse Effects of Protein Supplementation

• Several human and animal studies of protein supplementation have found adverse effects including retarded fetal growth, increase in prematurity, and increased neonatal deaths..

Cochran Collection: High protein supplementation in pregnancy

• Background and objectives: To assess the effects of providing pregnant women with high-protein nutritional supplements on gestational weight gain and on the outcome of pregnancy, including fetal growth, gestational duration, and maternal and fetal/infant morbidity and mortality.

Cochran Collection: High protein supplementation in pregnancy

• Selection criteria: All acceptably controlled comparisons of protein/energy supplementation in which the protein content of the supplement provided >25% of its total energy content.

Cochran Collection: High protein supplementation in pregnancy

• Main results: Two studies involving 1076 women were included. High protein supplementation was associated with a small, statistically nonsignificant increase in weekly maternal weight gain. The two available trials provide no evidence of benefit on fetal growth; indeed, the adjusted mean difference in birth weight is -58.4 g. One trial also reported a nonsignificantly increased risk of neonatal death with high-protein supplementation.

Cochrane Collection: Isocaloric balanced protein supplementation in pregnancy

• Main results: Three trials involving 966 women were included. The results suggest a decrease in maternal weight gain and mean birth weight and an increased risk of small-for-gestational-age (SGA) births with isocaloric protein supplementation, but no effect on mean gestational age or preterm birth. The data are insufficient to exclude potentially important effects on fetal or neonatal mortality, and maternal health outcomes have not been reported.

Cochrane Collection: Isocaloric balanced protein supplementation in pregnancy

• Reviewers' conclusions: Balanced protein supplementation alone (ie without energy supplementation) is unlikely to be of benefit to pregnant women or their infants.

Cochran Collection: Balanced protein/energy supplementation in pregnancy

• Background and objectives: To assess the effects of providing pregnant women with a 'balanced' protein/energy supplement (ie, a supplement in which the protein accounts for <25% of the total energy content) on gestational weight gain, the outcome of pregnancy, and postnatal infant outcomes.

• Studies were all in high risk women - mostly in developing countries

Cochran Collection: Balanced protein/energy supplementation in

pregnancy

• Main results: Fourteen studies were included. Balanced protein/energy supplementation results in modest increases in maternal weight gain and fetal growth. These increases do not appear larger in under-nourished women, although larger effects were reported in a recent trial in under-nourished women from the Gambia that provided much higher energy supplements. Beneficial effects on fetal and neonatal mortality have also been demonstrated. The available evidence is inadequate to reach conclusions

concerning effects on preterm birth or maternal health.

Cochran Collection: Balanced protein/energy supplementation in

pregnancy

• Reviewers' conclusions: Balanced energy/protein supplementation appears to reduce the risk of both fetal death (stillbirth) and neonatal death. Such supplementation also improves fetal growth, but the improvement appears modest unless the supplement provides a very large net increase in energy intake. The effect on fetal growth does not appear to be associated with long-term benefit to the offspring, and no benefit has been demonstrated on maternal health.

Lipids

• General– maternal– fetal

• LCPUFA

• Trans FA

Lipids: Maternal

• Metabolism changes to:– meet increased maternal needs for energy

and hormones precursors– to insure adequate fetal accretion

• Serum cholesterol rises 25-40%

• Triglycerides rise 200-400%

Lipids: Maternal Recommendations

• 30% of kcals from fat is a reasonable goal in pregnancy.– There is no need to try to affect the

physiological rise in blood lipids

Essential Fatty Acids in Pregnancy

• FAO recommends 4.5% of daily energy as EFA (essential fatty acids) in pregnancy and 6% in lactation– If kcals are inadequate energy based

recommendations may be misleading

2002 DRI for n-6 Fatty Acids in Pregnancy

• AI = 13 g/day linoleic acid

• Based on median linoleic acid intake of pregnant women in US where deficiency is “basically non-existent.”

• AI for non-pregnant women = 12 g/day

2002 DRI for N-3 Fatty Acids in Pregnancy

• Demand driven by:– fetus– placental tissue– secretion during lactation

• AI = 1.3 g/day of -linolenic acid – Based on median -linolenic acid intake of

pregnant women in US where deficiency is “basically non-existent.”

– non-pregnant AI=1.1 g/day -linolenic acid

– DHA and EPA can contribute toward total n-3

Lipids: Fetal

• Human brain is lipid based; ~ 60% of dry weight

• 30% of fetal CNS tissue is LCPUFA with n-3 to n-6 ratio of 2:1

• Fetal brain development starts early & experiences “growth spurt” during last trimester and 1st 6 months of life

• In 3rd trimester, storage of LCPUFA in fetal adipose tissue if adequate maternal sources

LCPUFA in Pregnancy

• Eicosanoids derived from LCPUFA (prostaglandins, thromboxanes, prostacylcins, leukotrienes) play vital roles in pregnancy

• Dietary sources of EFA - both n-3 and n-6 are important

• The ideal ratio of n-3 to n-6 remains unknown

Are n-3 fatty acids essential nutrients for fetal and infant development? (Nettleton, JADA 1993)

• Fetal and infant nutrition may be enhanced by encouraging pregnancy and lactating women to consume seafood regularly (2-3 meals per week)

• Poultry and plant sources of n-3 may be useful if seafood is impossible

• Avoid extreme dietary rations of n-6 to n-3 by using olive and canola in addition to corn and safflower oil.

PIH and n-3 Fatty Acids

• Possible biological pathway: – Vasoconstriction and epithelial damage of

PIH is associated with imbalance of TXA2

(vasoconstrictor) and PGI2 (vasodilator)

• If increased dietary intake of n-3:– EPA competes with Arachadonic Acid for

enzymes so may have lower production of TXA2 and higher production of PGI3 (vasodilator)

PIH and n-3 Fatty Acids

• Epidemiological Studies:– women with PIH may have lower levels of

n-3– lower incidence of PIH in fish eating

populations

• Evidence is not strong and EBM reviews only mention that more work needs to be done in this area

N-3 and Prolonged Gestation

• Faroe Islands: – high birthweights– longer gestations– diet high in marine oils

• Theory: n-3 interference with uterine prostaglandin production

N-3 and Prolonged Gestation

• Supplementation study: – increased gestational length by 4 days

– prolonged bleeding times & increased blood loss at delivery

Essential Fatty Acids in Mothers and

Their Neonates (Hornstra, AJCN, 2000)

• Maternal essential fatty acid status declines during pregnancy (absolute plasma levels in-crease, but non-essential increase more).

• Pregnancy may cause maternal DHA depletion/mobilization from maternal stores. (Implications for close pregnancy spacing)

• Essential PUFA status of newborns is restricted by that of the mother and may not be optimal.

• Maternal PUFA supplementation affects neonatal PUFAQ status.

• Maternal linoleate intake during pregnancy is negatively related to neonatal head circumference.

• In preterm infants positive relationship between DHA in umbilical artery and birth weight. Length, and OFC.

Hornstra - Implications

• Hunter-gatherer diet more rich in LCPUFA.

• Humans evolved with limited ability to elongate and desaturate EFA?

• Limitations require special consideration during increased requirements of fetal development, lactation, and neonatal development.

Trans Fatty Acids

• Side product of catalytic hydrogenation of vegetable oils and biohydrogenation in the rumen of animals

• Animal studies show discrimination against transport of trans FA across the placenta, but some are transported.

• Trans FA inhibit elongation of EFA• Trans FA in plasma of human preterm

infants was found to be inversely associated with LCPUFA

Trans Fatty Acids

• Infant formula has few trans FA, breastmilk content reflects maternal diet.

• What to recommend?

Trans Fatty Acids

“It may be prudent to reduce maternal intake of trans fatty acids as much as possible, even if negative effects of trans fatty acids on fetal development cannot yet be ascertained.”

Carlson et at. AJCN, 1997

Vitamins and Minerals

• Increased needs in pregnancy associated with:– DNA/RNA synthesis– Increased blood volume– bone mineralization & structure– Increased energy needs

Vitamins and Minerals

• Some nutrients of special concern due to low dietary levels in the population (from IOM report):– Vitamins B6, D, E– iron– calcium– zinc– magnesium

Vitamins and Minerals

• Risks for low vitamin and mineral status include:– low income– restricted energy intake– adolescence– vegan (Ca, B12, D, zinc)– Non white status (Ca)

Vitamins and Minerals

• Vitamin and mineral needs are increased by:– alcohol consumption– tobacco use– multiple fetuses– history of oral contraceptive use

Fat Soluble Vitamins

• Placental transport is by simple diffusion, so fetus is not protected against high maternal intakes

• Vitamin A is associated with multiple congenital anomalies – concerns appear to start at 8,000 IU – ACOG and AAP define excessive as >

1,600 RE (twice the RDA)– 1 IU = 0.3 RE all trans retinol

High levels of retinol intake during the first trimester of pregnancy result from use of over-the-counter vitamin/mineral supplements (Voyles et al. JADA, Sept., 2000)

• N=64 women recruited at initial prenatal visit to obstetrics office in university town.

• Household income and educational levels were higher than national averages.

• Women completed questionnaires and three day food records.

• 2 physicians in office prescribed routine prenatal vitamins, the third did not.

Voyles, cont. - Adherence

• 23% who were prescribed vitamins did not take them.

• 26 % who were prescribed vitamins took OTC supplements instead.

• 58% of those who were not prescribed took over the counter supplements.

• 9 of 10 women who had excessive intakes took OTC supplements

Voyles, Retinol Intakes (n=64)

• 20 had intakes < 800 RE

• 34 had intakes between 800 and 1,600 RE

• 10 had intakes > 1,600 RE

• Mean intake of vitamin A from food sources alone was 159% of the RDA

Voyles, Applications

• Most women can meet vitamin A needs with food alone.

• Supplements need to be carefully considered:

• many women taking OTC supps before pregnancy

• IOM recommendation is to avoid supps with vitamin A in first trimester

Fat Soluble Vitamins, cont.

• Vitamin D

• toxic levels: 2000 IUs (50 micrograms) per day

• Associated with fetal hypercalcemia, aortic stenosis, abnormal skull development/premature closure of fontanel

Water Soluble Vitamins - C

• Potential for dependency in the newborn (reported with vitamin C and B6)

• Vitamin C is actively transported across placenta as well as simple diffusion so potential for high fetal levels exists

• High maternal vitamin C levels associated with false positive tests for urinary glucose as well as cramps, nausea, and diarrhea

Water Soluble Vitamins - B6

• Inconclusive studies have linked to:– depression in pregnancy– decreased apgars with low maternal status– one study found good results for women

with severe nausea who were treated with 25 mg each 8 hours

• toxicity reported at > 200mg (neuropathy)

Folic Acid - NTD

• NTD - 2,500 births per year in US.• 50-70% may be preventable with

adequate maternal folic acid status.• Etiologies and pathways remain

unknown.• Some population groups - Mexican

Americans, Native Americans - at higher risk.

Folic Acid - Recommendations

• 1992 - USPHSD: women of childbearing age consume 400 mcg folic acid per day.

• 1998 - IOM: women consume 400 mcg synthetic folic acid per day from supplements or fortified foods.

• January 1998 - USFDA: fortification of the food supply at 140 mcg/100 grams of flour.

Folic Acid: Fortification

• 0.14 mg per 100g cereal grain products• 0.035 mg per slice of bread• 0.10 mg per serving breakfast cereal• Low level consumers with intakes of

0.23-0.25 mg.• Women with low intake range of food

guide pyramid will consume 0.5 mg per day total folate.

Folic Acid Supplements

• Dietary folate is about half as absorbable as synthetic folic acid.

• Public health recommendations have focused on message to all women of childbearing age to take a supplement of synthetic folic acid.

MMWR - Knowledge and use of folic acid,

1995-1997. Random digit dialing to 2000 women, ages 18-45

1995 1997

Non-pregnant, taking daily multivitamin with FA 25% 30%

Pregnant within last 2 years, taking daily multivitamin with FA 20 23

Aware of FA 52 66

Aware of PHS recommendations 15 22

Know that FA helps prevent birth defects 5 11

Know that FA should be taken before pregnancy 2 6

Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic

Acid, Biotin, and Choline (1999)

1999 Nonpregnant

1999pregnant

1989pregnant

Thiamin,mg 1.1 1.4 1.5

Riboflavin,mg

1.1 1.4 1.6

Niacin, mg 14 18 17

B6 mg 1.3 2.0 2.2

Folate, mcg 400 600 400(180 np)

B12, mcg 2.4 2.4 2.2

Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic

Acid, Biotin, and Choline (1999)

Non-pregnant(AI)

Pregnant(AI)

Pantothenicacid, mg

5 6

Biotin, mcg 30 30

Choline, mg 425 450

Iron

• Routine Supplementation

• Screening

• Treatment for Iron Deficiency Anemia

US Preventative Services Task Force

Prevalence: Hgb < 10 g/dl is present in 20-40% of pregnant women, due largely to expansion of blood volume.

Burden: observational data confirms modest associations between severe anemia and adverse maternal and infant outcomes.

Efficacy: Trials find improved hematological indices not improved clinical outcomes

US Preventative Services Task Force: Iron Supplementation in

PregnancySafety: Unintentional overdosing,

hemochromatosis, GI symptoms

Compliance: Prescribed Fe supps taken correctly by 70%, not at all by 10%

Recommendation: Evidence is insufficient to recommend for or against routine iron supplementation during pregnancy.

IOM

• Pregnancy requires an additional 6 mg Fe/day in T2 and T3

• Fe deficiency is common in pregnancy• Fe supps maintain Hgb levels during pregnancy.• Percentage of iron absorbed declines as the amount

given increases.• High does increase side effects and decrease

compliance.• Recommendation: Small dose (30mg) after 12

weeks for all pregnant women.

Cochrane Review of 20 Trials- 1999

• “Iron supplementation appears to prevent low haemoglobin at birth or at six weeks post-partum.”

• “Iron supplementation had no detectable effect on any substantial measures of either maternal or fetal outcome.”

Yes No Maybe Not enoughevidence

IOM - NAS(1990)

Nat'l PerinatalEpi Proj. -Oxford

US SurgeonGeneral(1988)

US preventiveServices TaskForce (1993)

FASEB(1991)

USPHS Ex.Panel onPrenatal care(1989)

CochranReview(1999)

Recommendations for Routine Iron Supplementation in Pregnancy

Iron: US Preventative Health Services Task Force (1997):

Screening• Screening for iron deficiency anemia using hemoglobin

or hematocrit is recommended for pregnant women and for high-risk infants

• The exact prevalence of iron deficiency anemia among pregnant women is uncertain:

– <2% of nonpregnant women aged 20-44 years may have iron deficiency anemia.

– low-income, pregnant U.S. populations: a low hemoglobin level and/or low hematocrit is present in 6% of white women and 17% of black women during the first trimester and in 25% of white women and 46% of black women during the third trimester.7

Iron: US Preventative Health Services Task Force (1997):

Screening• The high rates of anemia in pregnant women may not

be attributable to iron deficiency, however. In a large cohort of urban, low-income, mostly minority pregnant women, only 12.5% of anemic women were iron deficient

• Screening criteria for pregnancy:

– WHO: menstruating women, <12 g/dL; pregnant women, <11 g/dL

– CDC: <11 g/dL during the first and third trimesters and <10.5 g/dL in the second trimester

Iron: US Preventative Health Services Task Force (1997):

Screening• There is little evidence evaluating adverse effects from the

mild degree of anemia that is most often detected by screening asymptomatic persons in developed countries.

– In a Swedish cohort, anemic women (Hgb <12 g/dL) reported no increase in reported infections, fatigue, or other symptoms, but they were significantly more likely to report low work productivity compared to nonanemic women.

– In a small, randomized placebo-controlled trial of Welsh women with anemia (hemoglobin <10.5 g/dL) detected by population-based screening, iron therapy did not result in clinically or statistically significant improvements in psychomotor function tests, symptoms, or subjective well-being, despite increased hemoglobin concentrations.

Iron: US Preventative Health Services Task Force: Screening

• A hemoglobin analysis or hematocrit is recommended for pregnant women at their first prenatal visit

• There is insufficient evidence to recommend for or against repeated prenatal testing for anemia in asymptomatic pregnant women lacking evidence of

medical or obstetrical complications • Compared to other diagnostic tests, serum ferritin

has the best sensitivity and specificity for detecting

iron deficiency in patients found to be anemic.

Iron Deficiency Anemia: Recommended Guidelines for the Prevention, Detection, and Management

Among U.S. Children and Women of Childbearing Age (1994)

Institute of Medicine (IOM)

A. Screen for anemia at the first prenatal visit and treat as appropriate

1. If T1, Hgb & ferritin: Future eval if Hgb < 9.0 g/dl or between 9.0 and 10.9 with ferritin > 30

2. Do not treat with Fe when Hgb > 11.0 g.dl and serum ferritin is > 20 mcg/l

3. 30 mg Fe supp. If Hgb between 9.0-10.9 and ferritin 12-20 or Hgb > 11.0 and ferritin , 20 < 20

Iron Deficiency Anemia: Recommended Guidelines for the Prevention, Detection, and Management

Among U.S. Children and Women of Childbearing Age (1994)

Institute of Medicine (IOM)

4. 60-120 mg Fe if Hgb 9.0-10.9 and ferritin is < 12

5. If no response to Fe supp. Refer for additional eval.

Note: Blacks Hgb 0.80 less, also adjust for high altitude and cigarette smoking

Iron Deficiency Anemia: Recommended Guidelines for the Prevention, Detection, and Management

Among U.S. Children and Women of Childbearing Age (1994)

Institute of Medicine (IOM)

B. Screen for anemia at the second trimester visit and treat as appropriate

• Recommendation for supplement and referral are similar to first trimester, but upper Hgb cutoffs are 10.4 for upper level of supplementation and 10.5 for lower

Iron Deficiency Anemia: Recommended Guidelines for the Prevention, Detection, and Management

Among U.S. Children and Women of Childbearing Age (1994)

Institute of Medicine (IOM)

C. Screen for anemia at the third trimester visit and treat as appropriate

D. Screen high-risk women for anemia at the 4-6 week postpartum visit

• E. Advise on diet at each prenatal visit

• 1. Eat a varied diet of iron

Iron Deficiency Anemia: Recommended Guidelines for the Prevention, Detection, and Management

Among U.S. Children and Women of Childbearing Age (1994)

Institute of Medicine (IOM)

E. Advise on diet at each prenatal visit1. Eat a varied diet of iron rich foods

2. Items that inhibit absorption of iron (tea, coffee, whole-grain cereals[particularly bran], unleavened whole-grain breads and dried beans) should be consumer separately from iron rich foods.

Zinc - Adapted from Janet King 1999

• Severe maternal zinc deficiency is teratogenic in rats

• Zinc is available to the fetus from maternal tissues

• Both survey and experimental research on zinc in human pregnancy have inconclusive results due to issues of study design

Zinc - cont.

• Kirksey et al. AJCN, 1994: – Low income Egyptian women– Only 2 mg zinc available when look at

phytate-zinc molar ratio– 20% of variance of birthweight attributed to

plasma Zn in second trimester– 39% of variance of birthweight attributed to

maternal weight at 3 mos. gest.... and plasma Zn in second trimester

Zinc

• Poor maternal zinc status:

• limits fetal growth

• influences length of gestation

• increases risk of maternal complications

Zinc Absorption in Pregnancy(Fung et al, AJCN, 1997)

Dietary Znmg/day

%absorbed

Amountabsorbedmg/d

Pre-pregnancy

9.7 14.6 1.4

24-36weeks

11.8 18.9 2.2

34-36weeks

12.4 19.4 2.4

Zinc Absorption

• Reduced by:– phytate– supplemental iron

• GI diseases– Crohn’s– diarrhea disease– intestinal by-pass

Zinc metabolism

• Needs increased by hepatic sequestering and increased urinary losses:– trauma– infection– smoking– alcoholism– chronic strenuous exercise

Cochran Collection: Zinc, May 1997

• Background and objectives: It has been suggested that low serum zinc levels may be associated with abnormalities of labor, although this has not yet been established. The objective of this review was to assess the effect of zinc supplementation in pregnancy on maternal and fetal mortality and morbidity.

Cochran Collection: Zinc

• Main results: Five trials were included. Apart from possible reduction in induction of labor in the supplemented group, no differences were detected between routine supplementation of zinc and placebo or no zinc in pregnancy.

Cochran Collection: Zinc

• Reviewers' conclusions: There is not enough evidence to evaluate the use of routine zinc supplementation in pregnancy

Calcium

• Fetus requires 25 to 30 g calcium

• Most fetal calcium accretion in third trimester

• Maternal absorption, increases early in pregnancy and maternal Ca stores increases in preparation for third trimester demands

• 1,25(OH)2D concentrations increase in pregnancy

Calcium Absorption

Stage Absorption

Non- pregnant 27%

5-6 months ofpregnancy

54%

Term 42%

A longitudinal study of calcium homeostasis during human pregnancy

and lactation (Ritchie et al, AJCN, 1998) • N=14, white, middle-upper income well

nourished women who consumed ~1200 g Ca daily

• Exams:• prepregnancy• T1 (8-10 weeks of pregnancy• T2 (23-26 weeks)• T3 (34-36 weeks)• EL (6-10 weeks postpartum)• 5-2 months post menses

Total BodyBMD (g/cm2)

TrabecularBMD (mg/ cm3)

Prepregnancy 1.156 162.9

Postdelivery 1.162 163.7

EL 1.153 147.7

Postmenses 1.143 164.3

Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and

Fluoride (1999)Institute of Medicine (IOM

• Dietary calcium intake does not appear to influence changes in maternal bone mass during pregnancy

• There is a lack of a relationship between the number of previous pregnancies and BMD.

• Some studies find a positive relationship between number of children born and radial BMD, total body calcium, and risk of hip fracture.

Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and

Fluoride (1999)Institute of Medicine (IOM

“Adaptive maternal responses to fetal calcium needs include an enhanced efficiency of absorption, which is modulated through changes in calciotropic hormones. Thus, provided that dietary calcium intake is sufficient for maximizing bone accretion rates in the nonpregnant state, the AI does not have to be increased during pregnancy.”

Dietary calcium and pregnancy-induced

hypertension: is there a relation?

Ritchie LD, King, JC. Am J Clin Nutr. 2000:71(suppl):1371S-4S

Effect of routine calcium supplementation during pregnancy on relative risk (RR) of preeclampsia

Subgroup Typical RR (95% CI)

Low-risk (n = 6 trials) 0.79 (0.65, 0.94)

High-risk2 (n = 4 trials) 0.22 (0.11, 0.43)

Adequate-calcium diet 0.86 (0.71, 1.05)(900 mg/d)(n = 4 trials)

Low-calcium diet (<900 mg/d) (n = 6 trials) 0.32 (0.21, 0.49)

Those at high risk: teenagers, had had preeclampsia previously, had increased sensitivity to angiotension II, or had preexisting hypertension.

Effect of routine calcium supplementation during pregnancy on relative risk (RR) of high blood pressure

Subgroup Typical RR (95% CI)

Low-risk (n = 6 trials) 0.84 (0.76, 0.92)

High-risk2 (n = 3 trials) 0.35 (0.21, 0.57)

Adequate-calcium diet (900 mg/d) (n = 4 trials) 0.90 (0.81, 0.99)

Low-calcium diet 0.49 (0.38, 0.62) (<900 mg/d) (n = 5 trials)

.

Review Conclusions

• “Ca supplementation during pregnancy for women with deficient calcium intake is a promising preventive strategy for preeclampsia.”

Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and

Fluoride (1999)Institute of Medicine (IOM)

1999 non-pregnant(19-31)

1999pregnant

1989RDA(25-50)

Calcium(mg)

1000 (AI) 1000 (AI) 1200

Phosphorus(mg)

700 (RDA) 700 (RDA) 1200

Magnesium(mg)

310 (RDA) 350 (RDA) 320

Vitamin D(mcg)

5 (AI) 5 (AI) 10

Fluoride(mg)

3 (AI) 3 (AI) none

Calcium: IOM Recommendations

• If intake is < 600 mg:– Encourage increased dietary sources– Consider supplemental calcium

Cochran Collection: Magnesium

• Background and objectives: Many women, especially those from disadvantaged backgrounds, have intakes of magnesium below recommended levels. Magnesium supplementation during pregnancy may be able to reduce fetal growth retardation and pre-eclampsia, and increase birthweight. The objective of this review was to assess the effects of magnesium supplementation during pregnancy on maternal, neonatal and pediatric outcomes.

Cochran Collection: Magnesium

• Main results: Six trials involving 2637 women were included. Only one of these trials was judged to be of high quality. Compared with placebo, oral magnesium treatment from before the 25th week of gestation was associated with a lower incidence of preterm birth (odds ratio 0.71, 95% confidence interval 0.52 to 0.95). There was also less maternal hospitalization during pregnancy, fewer cases of antepartum hemorrhage, a lower incidence of low birthweight and small for gestational age infants. Poor quality trials are likely to have resulted in a bias favoring magnesium supplementation.

Cochran Collection: Magnesium

• Reviewers' conclusions: There is not enough high quality evidence to show that dietary magnesium supplementation during pregnancy is beneficial.