Table 2.

Characteristics of included studies

Author & Country	Participants		Methods	Results
	Age/number	Eligibility criteria	Nutrient assessed	Participants	Nutritional status
Jackson & Mathur (1991) USA	98 black & 28 non‐ black pregnant adolescents aged 13–19 years (mean 17 years)	None specified	Iron status	All participated in the Special Supplementary Nutrition Program for Women, Infants and Children	Black adolescents: mean 33.4 (+2.6)%; 71% had haematocrit values ≤ 34%Non‐black adolescents: mean 34.5 (+2.8)%; 54% had haematocrit values ≤ 34%
Wolfe et al. (1994) Canada	66 pregnant adolescents aged 14–19 years (17.1 + 0.15 years, mean + SEM)	None specified	Zinc	92% Caucasian; 85% primigravida; 32.0–38.4 weeks’ gestation (35.9 + 0.2, mean + SEM); GA 4.9 + 0.20 years (mean + SEM); none married; 65% transient; 83% consumed prenatal vitamin and/or mineral supplement	None had plasma 1 or hair zinc 2 levels below cut‐off values; none exhibited alkaline phosphatase activity less than lower limit of normal range, but 36% had activities greater than the upper limit 3
Gadowsky et al. (1995) Canada	58 pregnant adolescents aged 14–19 years (17.0 + 0.17 years, mean + SEM)	None specified	FolateIron statusVitamin B12 Zinc	88% Caucasian; 84% primigravida; 32.0–38.4 weeks’ gestation (35.9 + 0.2, mean + SEM); 98% had GA ≥ 2 years; none married; 67% transient; 61% smoked; 82% consumed prenatal vitamin and/or mineral supplement	Plasma folate: 7%/17.5% of adolescents had deficient/marginal status 4 Erythrocyte folate: 1%/7% of adolescents had deficient/marginal status 5 Vitamin B12: 20%/26% of adolescents had indeterminate/deficient status 6 Plasma ferritin: 78% had depleted iron stores 7 Haemoglobin: 22% were anaemic 8
Chang et al. (2003a) USA	918 pregnant adolescents aged 12–17 years (16.1 + 1.1, mean + SD)	African American adolescents who received prenatal care at an inner‐city maternity clinic; singleton pregnancy	Iron status	82.2% primiparous; 99.7% unmarried; 10% were smokers; 6% had pre‐ eclampsia; measurements taken in 1st, 2nd and 3rd trimesters	As pregnancy progressed the prevalence of anaemia increased, as assessed by Hb and haematocrit levels: 10–13% in 1st trimester; 20–33% in 2nd trimester; 57–66% in 3rd trimester 9
O’Brien et al. (2003) USA	23 pregnant adolescents aged 13–18 years (16.5 + 1.4, mean + SD)	Healthy primiparous adolescents with uncomplicated singleton pregnancies. No medical problems, no medications known to influence Ca metabolism, no reported history of drug or alcohol abuse, non‐smokers	Calcium status	32–36 weeks’ gestation (34.7 + 1.0, mean + SD); 20 African American, 3 white; 39% took prenatal supplements	Percentage calcium absorption averaged 53% during pregnancy. Calcium absorption was not significantly affected by age across the range of 13–18 years
Iannotti et al. (2005) USA	80 pregnant adolescents aged 13–18 years (16.5 + 1.1, mean + SD)	African American adolescents attending an inner‐city maternity clinic with singleton pregnancy	Iron statusFolateVitamin B12	73% primigravida; 31% <16 years old; GA 4.9 + 1.8 years; prior to pregnancy 53% overweight (BMI > 26.1 kg m– 2) & 9% underweight (BMI < 19.8 kg m– 2; high prevalence of genitourinary infections; 23 participants were studied longitudinally for iron status in the 2nd and 3rd trimesters. Unclear at what stage of pregnancy folate and vitamin B12 was assessed	Iron status: rise in prevalence of compromised iron status from 2nd to 3rd trimester reflected by all indicators of iron status 10 Folate: 88% had levels indicative of positive folate balance; 1 adolescent showed early folate depletion 11 Vitamin B12: none had depleted or deficient status 12

BMI, body mass index; CDC, Centers for Disease Control and Prevention; GA, gynaecological age (i.e. age in years past onset of menarche); Hb, haemoglobin; sTfR, serum soluble transferrin receptors; WHO, World Health Organization. ¹Based on 36‐week gestation cut‐off value (6.12 µmol L⁻¹) (Hambidge et al. 1983). ²Based on cut‐off value of 1.07 µmol g⁻¹. ³Based on lower and upper limits of normal range of <13 and >50 U L⁻¹, respectively. ⁴Based on cut‐off values of 7.0 nmol L⁻¹ indicating deficiency and 13.0 nmol L⁻¹ indicating marginal status (Bailey et al. 1980). ⁵Based on cut‐off values of <317 nmol L⁻¹ indicating deficiency and <362 nmol L⁻¹ indicating marginal status (Bailey et al. 1980). ⁶Based on ranges of 118–148 pmol L⁻¹ indicating indeterminate status and <118 pmol L⁻¹ indicating deficient status. ⁷Based on cut‐off values of 26.6 pmol L⁻¹. ⁸Based on the WHO classification system for anaemia in pregnancy (Hb < 110 g L⁻¹) (Stolzfus & Dreyfuss 1998). ⁹Based on CDC criteria for anaemia in pregnancy, i.e. Hb cut‐off values of 110 g L⁻¹ in first and third trimesters and 105 g L⁻¹ during second trimester. Corresponding haematocrit cut‐off points were 0.33 during first and third trimesters and 0.32 during second trimester (CDC 1989). Hb concentrations were adjusted for smoking status using CDC criteria (1989). ¹⁰Adolescents classified as having iron‐deficiency anaemia if serum ferritin concentration was ≤15 µg L⁻¹ and Hb concentration was<110 g L⁻¹ (1st & 3rd trimesters) or<105 g L⁻¹ (2nd trimester) (CDC 1989). CDC criteria (1989) were used to adjust for smoking status. Depleted iron stores were also indicated by serum ferritin concentrations ≤15 µg L⁻¹ (Perry et al. 1995) and a sTfR : serum ferritin ratio >300 (van den Broek et al. 1998). Tissue iron deficiency was defined when sTfR concentrations exceeded 8.5 mg L⁻¹ (Akesson et al. 1998). ¹¹Serum folate concentrations <6.80 nmol L⁻¹ were used to classify any of the stages of folate depletion or deficiency (Herbert 1967). ¹²Based on cut‐off values of <111 pmol L⁻¹ for B₁₂ depletion and <74 pmol L⁻¹ for B₁₂ deficiency (Herbert 1999).