Nutrient needs of the pregnant adolescent

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Nutrition screening and assessment is a cornerstone for comprehensive prenatal care for all pregnant adolescents. Adolescence is a period of rapid physical growth, with heightened nutritional requirements to support growth and development. The additional energy and nutrient demands of pregnancy place adolescents at nutritional risk [13]. The physiological and psychosocial immaturity of the teen compounds the potential for obstetric risks and complications [13]. Nutrition screening and counseling should be aimed at alleviating the risks and promoting optimal maternal and fetal outcomes.

Important assessment data that need to be collected and evaluated to comprehensively develop educational approaches for pregnant adolescents can be categorized as follows: (1) determining the quality, quantity, and rate of weight gain in pregnancy; (2) evaluating current dietary intake to determine the adequacy of nutrient and energy intake during pregnancy; and (3) assessing dietary issues that may affect intake, e.g., food allergies or vegetarianism [13]. Data derived from these assessments can provide a focus for discussions with all adolescents throughout pregnancy. Adolescents, especially those younger than 15 years of age, are at high risk for inappropriate maternal weight gain, anemia, and more serious complications such as lung and renal disease. Maternal weight gain is reportedly more influential than age of mother on fetal birth weight [11, 14]. Given that fetal birth weight < 3,000 g is related to increased infant morbidity and mortality, optimizing maternal weight gain should be central to any intervention efforts for the pregnant teen and adult.

Pregnancy places the adolescent at high nutritional risk because of the increased energy and nutrient demands of pregnancy. Data regarding nutrient requirements of pregnant adolescents are extremely limited. In general, however, the closer a teen is to menarche (younger teens with incomplete growth) at conception, the greater her need is for energy and nutrients above the normal requirements for pregnancy [15, 16]. The Institute of Medicine (IOM) Dietary Reference Intakes (DRIs) provide recommendations for nutrient and energy needs during pregnancy by trimester of pregnancy. Adequate energy intake should be a primary consideration for adolescent pregnancy; if energy needs are not met, then available protein, vitamins, and minerals cannot be used effectively in various metabolic functions [17]. Energy requirements may be greater for adolescents who begin pregnancy underweight, are still growing, or who are physically active [13]. The additional energy needs during the second and third trimesters of pregnancy are approximately 300 kcal per day in adults and older adolescents and 500 kcal per day in younger adolescents (aged 14 years and younger) [18, 19].

Protein needs are increased during pregnancy. The additional 25 g of protein required each day during pregnancy are generally not a problem to obtain for most adolescents in industrialized countries, given that many teens consume twice their recommended daily protein intake [20]. Routine ingestion of high-protein powders and specially formulated high-protein supplements and beverages are not routinely needed and may be potentially harmful (increasing risk of preterm birth) during pregnancy [17, 21]. These supplements should be avoided during pregnancy. Rather, increased use of food sources of protein is recommended, such as milk and flesh (meat) foods, as part of a well-balanced diet, especially because these foods are also rich sources of vitamins and minerals [21]. A careful assessment of dietary protein intake of a pregnant adolescent is important. About two thirds of total protein should be of high biologic quality, such as the protein that comes from eggs, milk, meat, or other animal sources [17].

Iron deficiency is one of the most common nutritional problems among both pregnant and nonpregnant adolescent females and occurs in all socioeconomic groups [17]. The need for iron increases during adolescence due to increased deposition of lean body mass, heightened synthesis of red blood cells, and onset of menses [17]. Iron requirements are further increased during pregnancy due to the rapidly expanding blood volume, which far exceeds the expansion of red blood cells, and results in decreased hemoglobin concentration [13]. The DRI for pregnant women is 27 mg per day, a level almost twice that for nonpregnant adolescents. The CDC recommends a routine low-dose iron supplement (30 mg per day) beginning at the first prenatal visit [22]. Although conclusive evidence for the benefits of universal supplementation is lacking, the CDC advocates this position because many women have difficulty maintaining iron stores during pregnancy [23]. Given the typically low intake of iron in most adolescent diets [17], supplemental sources of iron may be even more important for pregnant teens. Liquid and chewable forms of iron are available if teenagers have trouble swallowing tablets or capsules. To ensure adequate absorption, iron supplements should be taken at bedtime or between meals with water or juice; milk, tea, or coffee should be avoided, as these block iron absorption [24]. Pregnant adolescents should be encouraged to consume iron-rich foods such as lean red meat, fish, poultry, dried fruits, and iron-fortified cereals. Iron from animal sources is well absorbed. Iron from plant sources is poorly absorbed, but absorption is enhanced by simultaneous intake of vitamin C, meat, fish, and poultry [17]. If iron deficiency anemia develops, then iron supplementation is typically increased to 60 to 120 mg per day until the anemia is resolved. A multivitamin-mineral supplement supplying 15 mg of zinc and 2 mg of copper is also recommended because the therapeutic dosage of iron may impair the absorption or utilization of these nutrients [20].

Calcium is another nutrient of concern during pregnancy, especially among adolescents. The DRI for calcium for adolescents is 1,300 mg per day, yet 12- to 19-year-old females in the United States have average calcium intakes of about 800 mg per day [25]. Consumption of low-calcium beverages like soft drinks and fruit drinks displace milk and likely accounts for the suboptimal intakes reported [26]. The DRI for calcium does not increase during pregnancy, but adolescents may potentially have increased needs secondary to continued skeletal growth and consolidation of bone mass during the adolescent years [13]. Health professionals should counsel pregnant teens on good dietary sources of calcium and ways to meet the recommended intake. Dairy products and fortified foods including orange juice are high-quality calcium sources to recommend during counseling [17]. For pregnant teens that do not consume milk products (due to milk allergy or other reason) or calcium-fortified foods, a calcium and vitamin D supplement may be needed [23]. The IOM recommends taking a separate calcium supplement supplying 600 mg of elemental calcium per day. Most calcium supplements have comparable absorption rates, and two common forms include calcium citrate and calcium carbonate. Pregnant teens should be advised not to take supplements from bone meal calcium, dolomite, and calcium carbonate made from oyster shells, as these may contain lead [13]. For optimal absorption, supplements should be taken with meals and in doses no greater than 600 mg at a time [13].

Folate, essential for nucleic acid synthesis, is required in greater amounts during pregnancy, because of maternal and fetal tissue growth and red blood cell formation [15]. Folate deficiency during pregnancy may result in intrauterine growth restriction, congenital anomalies, neural tube defects, or spontaneous abortion [21, 23, 29]. The DRI for folate during pregnancy is 600 mcg per day [28]. The major natural sources of dietary folate are legumes, green leafy vegetables, liver, citrus fruits and juices, and whole wheat bread. Compared to naturally occurring folate in foods, the folic acid contained in fortified foods and supplements is almost twice as well absorbed, so that 1 mcg from these sources is equivalent to 1.7 mcg of dietary folate equivalents [23]. Because an adolescent's diet tends to be low in foods naturally high in folate, such as fruits and vegetables, nutrition counseling should focus on ways to incorporate both fortified foods and fruits and vegetables on a daily basis [13]. Most women are not able to meet the recommended intake of folate without supplements, and the general recommendation is to supplement with 400 mcg of folic acid per day both prior to and during pregnancy [13].

Fluid needs increase during pregnancy because of increased blood volume [17]. Adequate water helps the body maintain proper temperature, transports nutrients and waste products, moistens the digestive tract and tissues, and cushions and protects the developing fetus [17]. At least eight 8-oz cups of noncaffeinated fluids should be consumed each day. Water is the best choice, as the body absorbs it rapidly. Adolescents may obtain appreciable amounts of caffeine through consumption of soft drinks and coffee or tea beverages. Caffeinated beverages can increase urinary output, contributing to fluid depletion, and should be consumed in limited amounts [17]. High-caffeine intakes have been linked to low birth weight and increased risk of spontaneous abortion [23]. Prudent advice would be to discourage caffeine intake above 300 mg/day [23]. To translate that level into servings, this equates to the amount of caffeine in about two 8-oz cups of brewed coffee (135 mg/cup), three 8-oz cups of instant coffee (95 mg/cup), and six 8-oz cups of leaf/bag tea (50 mg/cup). The caffeine in a 12-oz soft drink ranges from 23 to 71 mg [17]. Newer "energy drinks" are often higher in caffeine and reading the labels is important.

Weight gain during pregnancy is a good assessment of the adequacy of an adolescent's dietary intake. How much should she gain? The IOM recommendations are 28-40 lb (12.5-18 kg) for women with body mass index (BMI) < 19.8, 25-35 lb (11.5-16 kg) for BMI = 19.8-26, 15-25 lb (7-11.5 kg) for BMI = 26-29, and at least 15 lbs (7 kg) for BMI > 29. Adolescents should gain at the upper end of these ranges. These recommendations were established in 1990, and several authors have suggested that they be revisited to evaluate long-term effects on infant and child health. [11] There is agreement, however, that weight gain should be based on prepregnancy BMI (kg/m2) to promote healthy outcomes, avoid postpartum weight retention, and reduce risk of chronic diseases in childhood and beyond [11, 13, 23]. The current recommendations by IOM are supported by the American College of Obstetricians and Gynecologists (ACOG). Maternal weight gain strongly influences fetal growth, infant birth weight, and length of gestation [21].

The recommendation for obese women to gain at least 15 lb is to reduce risk for delivering small for gestational age infants [13]. The American Dietetic Association (ADA) suggests that efforts should also be focused on assisting the postpartum adolescent to return to a healthy weight to reduce risk to future pregnancies [23]. There is no benefit in weight gain above the range suggested, and some indication of harm to mother and baby has been reported (see Chap. 5, "Obesity in Pregnancy"). Very young teens may be the exception to this for reasons discussed earlier regarding difficulties meeting nutrient recommendations. However, more studies are needed to determine whether changes to the IOM recommendations are warranted for the adolescent.

The overall issue of weight gain may be problematic for teens responding to the "skinny" image presented in pervasive media. Croll in Guidelines for Adolescent Nutrition Services [30] presents an entire chapter dedicated to body image issues and tools to assist teens to establish a healthy appreciation for their unique appearance. She suggests that routine patient counseling should include assessment for body image concerns, and if present, teens should be provided with appropriate resources to address these issues. In her book, Croll provides specific questions to use in assessing body image, and suggests several strategies and tools to use with teens and their parents on body distortion, dieting, and media literacy. The same source [30] also has a chapter by Alton on eating disorders and offers diagnostic criteria and treatment information for these psychiatric syndromes with disturbed body images.

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