Vitamin B6 nutriture during pregnancy and lactation. I. Vitamin B6 intake, levels of the vitamin in biological fluids, and condition of the infant at birth.

Vitamin B6 nutriture was assessed during pregnancy and lactation to determine possible relationships among vitamin B6 intake, levels of the vitamin in biological fluids and the condition of the infant at birth. Vitamin B6 levels were measured in maternal serum and in urine at 5 and 7 months gestation and at delivery, in cord serum and in milk at 3 and 14 days postpartum. Intake of vitamin B6, less than the Recommended Dietary Allowances (1974) for pregnancy and lactation, 2.5 mg/day, resulted in lower levels of the vitamin in maternal serum at delivery and in cord serum than higher intakes. Mothers whose infants had unsatisfactory Apgar scores at 1 min, (less than 7) had significantly low intakes of vitamin B6 and lower levels of the vitamin in both serum and milk than mothers whose infants had satisfactory scores, (greater than or equal to 7). At 5 months gestation, levels of vitamin B6 in maternal serum were significantly correlated with levels of the vitamin in cord serum and in milk at 14 days postpartum. This stage of gestation precedes the period of rapid growth of the central nervous system of the fetus, and is, therefore, a critical time for the assessment of maternal vitamin B6 nutriture.

Vitamin B6 nutriture during pregnancy and lactation. II. The effect of long-term use of oral contraceptives.

Vitamin B6 nutriture was assessed during pregnancy and lactation to determine whether previous use of oral contraceptive agents (OCA) resulted in reduced reserves of the vitamin. Vitamin B6 levels were measured in maternal serum and urine at 5 and 7 months gestation and at delivery, in cord serum and in milk at 3 and 14 days postpartum. Long-term use of OCA (greater than 30 months) resulted in low levels of vitamin B6 in maternal serum at 5 months gestation and at delivery and in milk compared with values for short-term (1 to 30 months) and nonusers of OCA. Levels of vitamin B6 were also lower in the cord serum of long-term users of OCA as compared to nonusers.

PIP: A study involving 106 women was conducted to determine whether pregnant and lactating women experienced vitamin B6 deficiency after using oral contraceptives. Maternal serum and urine were measured at 5 and 7 months gestation and at delivery, in cord serum, and in milk at 3 and 14 days postpartum to measure vitamin B6 levels. Among 13 long-term pill users (greater than 30 months), the mean vitamin B6 level in maternal serum at 5 months gestation was 8.1 ng/ml; for 44 short-term pill users (1-30 months), 13.7 ng/ml; and for 49 nonusers, 16.6 ng/ml. Long-term pill users also had significantly lower vitamin B6 levels at delivery, in cord serum, and in milk at 14 days postpartum than nonusers, and lower B6 levels at delivery and in milk at 14 days than short-term pill users.

Diurnal variations in folacin levels of human milk: use of a single sample to represent folacin concentration in milk during a 24-h period.

Studies of breast-feeding and its adequacy for the infant could be simplified if a single milk sample were representative of nutrient levels during a 24-h period, despite diurnal variation. In this study, free and total folacin levels were measured in samples collected from 27 well-nourished mothers at each infant feeding from 2 wk to 1 yr of lactation. Folacin levels were higher (p less than 0.05) in the afternoon and evening than in the morning; variations decreased as lactation progressed (greater than 8 mo) and paralleled the decreased number of daily feedings. Despite 2- to 3-fold variations in milk folacin levels occur a 24-h period during the first 10 mo of lactation, the level in a single sample obtained at 1300-1450 h was representative (r = 0.74-0.93) of mean folacin concentration in samples obtained from all feedings during a 24-h period.

Changes in specific nutrients in breast milk during extended lactation.

An increasing trend towards breast-feeding infants beyond 6 mo of age has been observed in this country. The present study was designed to examine the effect of extended lactation on the concentrations of vitamins B6 and C, free and total folacin, calcium, zinc, and magnesium. Forty mothers were studied from 7 months of lactation until they stopped breast-feeding. Subjects were requested to collect milk samples monthly at a morning feeding between 7 AM and 10 AM. Between 7 and 25 mo of lactation, levels of zinc, calcium, vitamin B6, and vitamin C tended to decrease, whereas levels of free and total folacin remained unchanged. Magnesium levels decreased only after 18 mo of lactation. The decrease in concentrations of zinc and calcium paralleled the decrease in feeding frequency. Changes observed in this study on the composition of human milk may reflect physiological changes in the mammary gland during weaning.

Influence of mineral intake and use of oral contraceptives before pregnancy on the mineral content of human colostrum and of more mature milk.

PIP: The effects of mineral intake and long-term oral contraceptive use before pregnancy on the mineral content of milk of healthy lactating women were evaluated in a study of 52 volunteers ages 18-31. Subjects reporting previous oral contraceptive use had significantly lower levels of copper in serum, perhaps reflecting reduced copper stores resulting from prolonged estrogen exposure, but concomitant changes in copper levels in their milk were not noted. Serum calcium and magnesium levels were not significantly affected by prior pill use. Pill use had no significant effect on concentrations of calcium, magnesium, zinc, copper, or iron in colostrum at day 3 or more mature milk at day 14 of lactation, while mean manganese levels were significantly lower at both times for previous oral contraceptive users (but still exceeded manganese levels recommended for infants). Mineral and vitamin supplementation significantly improved the levels of zinc and iron intake, but did not appreciably alter the mineral content of milk. Higher levels of zinc were found in colostrum compared to day 14 milk, while manganese concentrations increased significantly during the 1st 2 weeks of lactation. Calcium, magnesium, iron and copper levels did not change significantly as lactation progressed. Levels of calcium, magnesium, zinc, copper, and manganese in colostrum were significantly positively correlated with the mineral concentration on day 14. No significant diurnal or daily variation was observed in the levels of calcium, magnesium, or zinc content in milk during 2 24-hour periods.^ieng