Adequacy of vitamin B6 supplementation during pregnancy: a prospective study. Effect of maternal pyridoxine X HCl supplementation on the vitamin B-6 status of mother and infant and on pregnancy outcome. Vitamin B-6 status of breast-fed neonates: influence of pyridoxine supplementation on mothers and neonates. Assessment of vitamin B-6 status in young women consuming a controlled diet containing four levels of vitamin B-6 provides an estimated average requirement and recommended dietary allowance. Preconception homocysteine and B vitamin status and birth outcomes in Chinese women.
This prospect i ve study assesses the effect of 2.5 , 4 , and 10 mg of pyridoxine supplementation during pregnancy  on  maternal and fetal plasma levels of pyridoxal 5'-phosphate ( PLP ) and on the degree of coenzyme saturation ( activation factor ) of aspartate aminotransferase and alanine aminotransferase ( alphaEGOT and alphaEGPT ) in maternal erythrocytes . More than 4 mg of pyridoxine supplementation daily was required for most pregnancies to maintain maternal plasma PLP levels within the range observed during the first trimester and in the nonpregnant state . The plasma PLP concentrations in maternal and cord blood were highly correlated and indicated a dependence of fetal vitamin B6 nutrition on maternal circulating PLP . Measurements of alphaEGOT and alphaEGPT were not as reproducible as plasma PLP assays and were less sensitive and quantitative indicators . In the majority of subjects , the changes in alphaEGOT and alphaEGPT with time correlated poorly with the changes in plasma PLP . However , when the data were analyzed without regard for their dependence on time , they demonstrated a negative , linear correlation between alphaEGOT and log plasma PLP and between alphaEGPT and log plasma PLP for the group on 2.5 mg of pyridoxine and for all the subjects combined . Finally , the dietary records showed that most of the subjects consumed less than 2 mg of vitamin B6 daily from their food . The results indicate that the current Recommended Dietary Allowance for vitamin B6 during pregnancy ( 2.5 mg ) is too low and that supplementation of this vitamin in an amount more than 4 mg daily is recommended The effect of maternal pyridoxine X HCl ( PN-HCl ) supplementation on the vitamin B-6 status of pregnant women and their infants at birth and on pregnancy outcome was investigated . Volunteer subjects were r and omly assigned a daily vitamin B-6 supplement containing 0 , 2.6 , 5 , 7.5 , 10 , 15 or 20 mg of PN-HCl in a double-blind study . The mean dietary vitamin B-6 intake of the group was 1.43 + /- 1.28 mg/day as estimated from 24-hour dietary recalls . Maternal plasma pyridoxal 5'-phosphate ( PLP ) levels were positively correlated with vitamin B-6 supplementation at 30 weeks gestation ( r = 0.55 , P less than 0.0005 ) and at delivery ( r = 0.54 , P less than 0.01 ) . Cord plasma PLP levels reached a maximum when maternal PN-HCl supplementation was 7.5 mg and greater . Supplemental PN-HCl at the 7.5-mg level was required to prevent a decrease in maternal plasma PLP at delivery . Apgar scores at 1 minute after birth were higher ( P less than 0.05 ) for infants whose mothers took 7.5 mg or more supplemental PN-HCl than for infants of mothers who took 5 mg or less . These findings indicate that a vitamin B-6 intake between 5.5 and 7.6 mg/day ( diet plus supplement as pyridoxine equivalents ) was required to maintain maternal plasma PLP levels at term at a level comparable to initial values Vitamin B-6 concentrations in human milk are known to respond rapidly to changes in maternal vitamin B-6 intake . In this study , mothers were supplemented during the first 28 d of lactation with 2 or 27 mg pyridoxine (PN)-HCl/d and a subgroup of breast-fed infants of the 2-mg/d-supplemented mothers were supplemented with 0.4 mg PN-HCl/d . Vitamin B-6 intakes of breast-fed infants reflected the amount of their mother 's supplement ; intakes were highest for the vitamin-supplemented infants . Vitamin B-6 intake of mothers was a strong indicator of infant vitamin B-6 status . Vitamin intake of infants correlated significantly with five measures of vitamin B-6 status . Plasma pyridoxal-5'-phosphate ( PLP ) concentrations and birth weight were the strongest predictors of infant growth that were examined . Alkaline phosphatase activity in the mother 's milk and infant plasma reflected pyridoxal-PLP ratios in these fluids , suggesting that the enzyme acts in regulating circulating vitamer concentrations The Recommended Dietary Allowance ( RDA ) of vitamin B-6 for young women was recently reduced from 1.6 to 1.3 mg/d based on an adequate plasma pyridoxal phosphate ( PLP ) concentration of 20 nmol/L. To assess vitamin B-6 requirements and suggest recommendations for intake , seven healthy young women consumed a controlled diet providing 1.2 g protein/kg body weight for a 7-d adjustment period ( 1.0 mg vitamin B-6/d ) and three successive 14-d experimental periods ( 1.5 , 2.1 and 2.7 mg/d , respectively ) . Direct and indirect  vitamin B-6 status indicators were measured in plasma , erythrocytes and urine . Indicators most strongly correlated with vitamin B-6 intake [ i.e. , plasma and erythrocyte PLP , urinary 4-pyridoxic acid ( 4-PA ) and total vitamin B-6 ] were regressed on vitamin B-6 intake and the dietary vitamin B-6 to protein ratio . Inverse prediction using adequate and baseline values estimated vitamin B-6 requirement . Adequate values were determined for plasma PLP and urinary 4-PA from baseline values of 60 previous subjects , using the statistical method suggested by Sauberlich . The current study suggests a  vitamin B-6 Estimated Average Requirement ( EAR ) for young women of 1.1 mg/d or 0.016 mg/g protein , and a RDA of 1.5 mg/d or 0.020 mg/g protein . When results from this study are combined with data from four other recent studies , the combined data predict an EAR of 1.2 mg/d or 0.015 mg/g protein , and a RDA of 1.7 mg/d or 0.018 mg/g protein . This study suggests that the current vitamin B-6 RDA may not be adequate BACKGROUND The associations between homocysteine , B vitamin status , and pregnancy outcomes have not been examined prospect ively . OBJECTIVE We assessed the associations of preconception homocysteine and B vitamin status with  preterm birth and birth of low-birth-weight ( LBW ) and small-for-gestational-age ( SGA ) infants in Chinese women . DESIGN This was a case-control study of women aged 21 - 34 y. Preterm cases ( n = 29 ) delivered living infants at < 37 wk gestation ; term controls ( n = 405 ) delivered infants at > or = 37 wk . LBW cases ( n = 33 ) had infants weighing < 2500 g ; normal-birth-weight controls ( n = 390 ) had infants weighing > or = 2500 g. SGA cases ( n = 65 ) had infants below the 10th percentile of weight-for-gestational-age ; appropriate-for-gestational-age controls ( n = 358 ) had infants above this cutoff .  Nonfasting plasma concentrations of homocysteine , folate , and vitamins B-6 and B-12 were measured before conception . RESULTS Elevated homocysteine ( > or = 12.4 micro mol/L ) was associated with a nearly 4-fold higher risk of preterm birth ( OR : 3.6 ; 95 % CI : 1.3 , 10.0 ; P < 0.05 ) . The risk of preterm birth was 60 % lower among women with vitamin B-12 > or = 258 pmol/L than among vitamin B-12-deficient women ( OR : 0.4 ; 95 % CI : 0.2 , 0.9 ; P < 0.05 ) and was 50 % lower among women with vitamin B-6 > or = 30 nmol/L than among vitamin B-6-deficient women ( OR : 0.5 ; 95 % CI : 0.2 , 1.2 ; NS ) . Folate status was not associated with preterm birth , and homocysteine and B vitamin status were not associated with LBW or SGA status . CONCLUSIONS Elevated homocysteine and suboptimal vitamin B-12 and B-6 status may increase the risk of preterm birth . These results need to be confirmed in larger prospect i ve studies
BACKGROUND Vitamin B6 plays vital roles in numerous metabolic processes in the human body , such as nervous system development and functioning .
It has been associated with some benefits in non-r and omised studies , such as higher Apgar scores , higher birthweights , and reduced incidence of pre-eclampsia and preterm birth .
Recent studies also suggest a protection against certain congenital malformations .
OBJECTIVES To evaluate the clinical effects of vitamin B6 supplementation during pregnancy and /or labour .