**6. Maternal vitamin D status and fetal and postnatal outcomes**

A growing body of evidence suggests that maternal vitamin D deficiency is associated with not only pregnancy outcomes, but also later physical and mental health of the offspring. In this section, we aim to review the existing literature investigating the impact of maternal vitamin D status during pregnancy on a range of fetal and postnatal outcomes.

#### **6.1 Fetal skeletal development**

During pregnancy, the fetus relies on maternal supply and placental delivery of vitamin D and calcium for optimal development and function, particularly of the skeletal system [154]. Maternal vitamin D deficiency during pregnancy predisposes breast-fed infants to neonatal hypocalcemia and infantile rickets [155, 156]. It has been reported that maternal UV-B exposure in pregnancy is related to bone mineral content (BMC) and bone mineral density (BMD) at age 9.9 years independently of height and lean mass [157]. Further, winter newborns in Korea were found to have 6% lower total body BMC, lower cord serum 25(OH)D and 1,25-dihydroxyvitamin D than summer newborns [158]. These results suggest that low maternal vitamin D concentrations due to limited UV-B exposure may exert direct effects on offspring bone mineral accrual.

The influence of maternal vitamin D status on bone outcomes has been investigated in several observational studies at fetal [159–161], postnatal [162–164], and adult stages [115, 165–167]. Using data from a prospective longitudinal study, Mahon et al. observed that lower maternal 25(OH)D concentration was associated with the

**45**

*Maternal Vitamin D Status among Different Ethnic Groups and Its Potential Contribution…*

greater femoral metaphyseal cross-sectional area at 19 weeks gestation and 34 weeks gestation. However, lower maternal 25(OH)D concentration was not related to fetal femur length [159]. In another prospective longitudinal study, Young et al. found a significant positive association between maternal 25(OH)D levels and fetal femur and humerus z-scores only when maternal calcium intake was <1050 mg/d [160]. It has also been reported that maternal serum 25(OH)D concentration, together with maternal height and adiposity, was significant predictors of femoral size [161]. In a cross-sectional study with a longitudinal follow-up, tibia BMC was 0.047 g/cm higher,

cord serum 25(OH)D above the median (42.6 nmol/L) compared with below median newborns [162]. In another study, Morley et al. found smaller knee-heel length in infants of mothers with low 25(OH)D levels (<28 nmol/L) in late pregnancy (28– 32 weeks of gestation) compared to babies whose mothers had higher concentrations [163]. Dror et al. reported no association between feto-maternal vitamin D status and early infant whole-body BMC. However, a large percentage of mothers in their study had adequate vitamin D status, which may have affected the results [164]. These observations suggest that maternal vitamin D status during pregnancy can influence

Emerging evidence suggests that the relationships between maternal vitamin D status and bone outcomes persist into childhood and beyond [115, 165, 166]. In a longitudinal study by Javaid et al., it was found that reduced concentration of maternal 25(OH)D during late pregnancy was associated with reduced wholebody and lumbar-spine BMC in children at age 9 years. Besides, childhood bone mass was predicted by maternal use of vitamin D supplements and the estimated exposure to UV-B radiation during late pregnancy [165]. Zhu et al., in a study of 341 mother and offspring pairs, found a positive association between maternal 25(OH)D concentration and total body BMC and BMD in offspring at 20 years of age [115]. These results were confirmed in another study where maternal vitamin D deficiency (25(OH)D < 50 nmol/L) during pregnancy was associated with lower peak bone mass at 20 years [166]. In contrast to these studies, Lawlor and colleagues observed no relevant association between vitamin D deficiency in pregnant women and offspring's BMC in late childhood [167]. In another study, compared to children born to mothers with high vitamin D status, tibial BMC was lower at birth in children with low maternal vitamin D status, while BMC gain was greater, resulting in similar BMC at 14 months [168]. The evidence derived from observational studies, although conflicting, tends to suggest an association between vitamin D deficiency in pregnant women and reduced bone mineral accrual in the offspring, which may

**6.2 Birth anthropometry, small-for-gestational-age (SGA), and childhood** 

Inconsistencies in the literature have led several researchers to conduct meta-analyses to further clarify the association between maternal vitamin D concentrations and anthropometric outcomes in offspring. Four meta-analyses of observational studies have been published in recent years [45, 52, 180, 181]. In

between 25(OH)D levels and head circumference [171, 174].

There is controversy regarding the relationship between maternal vitamin D status and neonatal birth weight, with some studies reporting an association between reduced maternal vitamin D levels and lower neonatal birth weight [169–174], and others showing no association [175–178]. While some studies found no association between maternal vitamin D levels and other anthropometric birth outcomes such as length and head circumference [176–179], others suggested a nonlinear relation

fetal bone growth as early as the second trimester of pregnancy.

larger in newborns with the first trimester and

*DOI: http://dx.doi.org/10.5772/intechopen.90766*

and cross-sectional area was 12.3 mm2

increase fracture risk in later life.

**growth**

#### *Maternal Vitamin D Status among Different Ethnic Groups and Its Potential Contribution… DOI: http://dx.doi.org/10.5772/intechopen.90766*

greater femoral metaphyseal cross-sectional area at 19 weeks gestation and 34 weeks gestation. However, lower maternal 25(OH)D concentration was not related to fetal femur length [159]. In another prospective longitudinal study, Young et al. found a significant positive association between maternal 25(OH)D levels and fetal femur and humerus z-scores only when maternal calcium intake was <1050 mg/d [160]. It has also been reported that maternal serum 25(OH)D concentration, together with maternal height and adiposity, was significant predictors of femoral size [161]. In a cross-sectional study with a longitudinal follow-up, tibia BMC was 0.047 g/cm higher, and cross-sectional area was 12.3 mm2 larger in newborns with the first trimester and cord serum 25(OH)D above the median (42.6 nmol/L) compared with below median newborns [162]. In another study, Morley et al. found smaller knee-heel length in infants of mothers with low 25(OH)D levels (<28 nmol/L) in late pregnancy (28– 32 weeks of gestation) compared to babies whose mothers had higher concentrations [163]. Dror et al. reported no association between feto-maternal vitamin D status and early infant whole-body BMC. However, a large percentage of mothers in their study had adequate vitamin D status, which may have affected the results [164]. These observations suggest that maternal vitamin D status during pregnancy can influence fetal bone growth as early as the second trimester of pregnancy.

Emerging evidence suggests that the relationships between maternal vitamin D status and bone outcomes persist into childhood and beyond [115, 165, 166]. In a longitudinal study by Javaid et al., it was found that reduced concentration of maternal 25(OH)D during late pregnancy was associated with reduced wholebody and lumbar-spine BMC in children at age 9 years. Besides, childhood bone mass was predicted by maternal use of vitamin D supplements and the estimated exposure to UV-B radiation during late pregnancy [165]. Zhu et al., in a study of 341 mother and offspring pairs, found a positive association between maternal 25(OH)D concentration and total body BMC and BMD in offspring at 20 years of age [115]. These results were confirmed in another study where maternal vitamin D deficiency (25(OH)D < 50 nmol/L) during pregnancy was associated with lower peak bone mass at 20 years [166]. In contrast to these studies, Lawlor and colleagues observed no relevant association between vitamin D deficiency in pregnant women and offspring's BMC in late childhood [167]. In another study, compared to children born to mothers with high vitamin D status, tibial BMC was lower at birth in children with low maternal vitamin D status, while BMC gain was greater, resulting in similar BMC at 14 months [168]. The evidence derived from observational studies, although conflicting, tends to suggest an association between vitamin D deficiency in pregnant women and reduced bone mineral accrual in the offspring, which may increase fracture risk in later life.
