Table 10. The effect of maternal vitamin D status in gestation on offspring birth length– Observational studies.

First Author and year	Bias score	Study Details	Study Type	Confounders/ adjustments	Number of weeks gestation when 25(OH)D was measured	Mean (SD) or median (IQR) 25(OH) D concentration (nmol/l)	Mean (SD) or median (IQR) birth length (cm)					Unadjusted regression co-efficient β (95% CI) for birth length (cm) per 1nmol/l increase in 25(OH)D	Adjusted regression coefficient β (95% CI) for birth length (cm) per 1 nmol/l increase in 25(OH)D	Conclusion
Ardawi, 1997 87	5 (low)	Jeddah, Saudi Arabia Cohort size=264 women	Cohort	nil	Delivery	47.71 (15.77) 25(OH)D <20 nmol/l in 23% 25(OH)D >20 nmol/l in 77%			25(OH)D <20 nmol/l (n=24)		25(OH)D >20 nmol/l (n=240)	Not given	Not given	No difference in offspring birth length in mothers with 25(OH)D <20 nmol/l at delivery compared to those with 25(OH)D >20nmol/l
							Birth length (cm)		51.7 (2.9)		51.0 (2.4)
Sabour, 2006 88	−2 (high)	Tehran, Iran n=449 women	Cross- sectional	Nil	Not measured directly Estimated from validated dietary FFQ at delivery (unclear when assessed)	Not measured Mean vitamin D intake = 90.4 (74.8) IU/day	Overall group mean (SD)			34.81 (6.55)		Not given	Not given	Offspring birth length significantly higher in mothers with adequate dietary vitamin D intake compared to those with inadequate intake p=0.03
							Vit D intake <200 IU/day			49.5 (3.77)
							Vit D intake >200 IU/day			50.37 (2.73)
Mannion, 2006 83	1 (med)	Calgary, Canada n=279 women, 207 women restricted milk intake (≤250ml milk) which equates to ≤90 IU vitamin D and 72 not restricting milk intake	Cohort		Not measured directly Repeat 24 hour dietary telephone recall. 3 or 4 times during pregnanc y (1 cup of milk = 90 IU vitamin D)	In those not restricting milk, Vitamin D intake= 524 (180)IU/day In those restricting milk, <2.25mcg/day per day, vitamin D intake=316 (188)IU/day	In those not restricting milk, unadjusted birth length= 51.4 (3.6) In those restricting milk, unadjusted birth length= 51.1 (3.5) P (diff. between groups)=0.46					Not given	Not given	No difference in offspring birth length in mothers restricting milk intake in pregnancy compared to those with unrestricted intake
Morley, 2006 91	8 (low)	Melbourne, Australia n=374 women (232 recruited in winter, 127 in summer)	Cohort	Sex, maternal height, whether first child, smoking, season of blood sample	11 weeks and 28-32 weeks	Winter recruitment, geometric mean at 11 wks=49.2; 26-32 wks=48.3 Summer recruitment geometric mean at 11 weeks=62.6; 26-32 wks=68.9		25(OH)D<28 (nmol/l) at 28-32 wk	25(OH)D >28 (nmol/l) at 28-32 wk	Diff (95% CI)	Adj Diff (95% CI)	At 28-32 wks β for every Log2 increase in 25(OH)D = −0.3 (−0.08−0.6)	At 28-32 wks β for every Log2 increase in 25(OH)D = −0.3 (−0.1−0.6))	No significant association seen between Log 25(OH)D at 11 wks (data not given) or 28-32 wks and offspring birth length
							BL	49.8 (2.7)	50.4 (2.4)	−0.6 (−1.5−0.3)	−0.6 (−1.5−0.3)
Magbooli, 2007 89	1 (med)	Tehran, Iran n=552 women	Cross- sectional	None	Delivery*	27.82 (21.71)*	50.02 (1.58)					Not given	Not given	No significant association seen between serum 25(OH)D3 and offspring birth length p not given
Clifton-Bligh, 2008 92	6 (low)	New South Wales, Australia n=307 women (included 81 women with GDM)	Cohort	Gestational age	Mean (SD) 28.7 (3.3) weeks	53.8 (23.9)	Not given					Not given	Not given	No association between maternal 25(OH)D and offspring birth length p>0.4
Gale, 2008 25	4 (med)	Princess Anne Cohort, Southampton , UK n=466 women	Cohort	Gestational age, maternal age, maternal BMI, ethnicity and parity	Late pregnancy Median 32.6 weeks (32.0-31.4)	50 (30-75.3) 50.4% had 25(OH)D >50nmol/l 28.3% had levels 27.5-50 nmol/l 21.1% had levels <27.5 nmol/l	Not given					β per Log 25(OH)D increase = 0.23 (−0.09, 0.54) p=0.150	β per Log 25(OH)D increase = 0.18 (−0.10, 0.46) p=0.215	No association seen between maternal serum 25(OH)D and offspring birth length
Farrant, 2009 90	5 (low)	Mysore Parthenon Study, India n=559 women (included 34 women with GDM)	Cohort	Maternal age, fat mass, diabetes status	30 (+/− 2) weeks	37.8 (24.0-58.5) 60% of women ha d 25(OH)D <50 nmol/l, 31% below 28 nmol/l	Geometric mean =48.9 (2.2)					β per Log 25(OH)D increase= −0.07 (−0.34, 0.20) p=0.6	β per Log 25(OH)D increase= −0.27 (−0.80, 0.26) p=0.3	No association seen between late pregnancy maternal Log serum 25(OH)D and offspring birth length when data analysed both continuously or dividing the group into categories using 25(OH)D <50nmol/l as a threshold (p=0.9)
Prentice, 2009 95	5 (low)	Gambia, Africa Subset of pregnant Gambian women participating in a calcium supplement trial n=125 women	Cohort	Season, mat height, weight, weight gain, infant sex and whether received calcium supplement	20 weeks and 36 weeks	20 weeks = 103 (25) 36 weeks = 111 (27)	50.5 (1.9)*					0.0634 (0.136) p=0.36	0.0736 (0.138) p=0.30	No significant association seen between maternal 25(OH)D and offspring birth length when analysed both continuously and categorically (25(OH)D >80 nmol/l vs <80 nmol/l)
Sayers, 2009 42	3 (med)	ALSPAC, cohort, UK n=10584 women	Cohort	Nil	Not directly measured Ambient UVB measured during 98 days preceding birth	Not measured	Boys (n=5447)=50.93 (2.61) Girls (n=5140)=50.19 (2.44)					β per 1 SD increase in UVB 0.10 (0.05-0.15) p=0.00004	No adjustments made	Maternal UVB exposure in late pregnancy is positively associated with offspring birth length
Leffelaar, 2010 82 **	4 (med)	Amsterdam Born Children and their development (ABCD) study cohort=3730 women, all term offspring (≥37 wks)	Cohort	Gestational age, season of blood sampling, sex, maternal height, maternal age, smoking, pre-pregnancy BMI, educational level, ethnicity, smoking, parity	Early pregnancy (mean 13 weeks)	54.4 (32-78) Group divided by serum vitamin D concentration as follows: Adequate; ≥50 nmol/l (median 73.3) Insufficient;30 −49.9 (median 40.4) Deficient ≤29.9 (median (19.9)		All	25(OH)D≤29.9	25(OH)D 30-49.9	259OH)D ≥50	Not given	Not given	Infants born to mothers with 25(OH)D ≤29.9 nmol/l (deficient) had lower length at 1 month. No difference between birth length in mothers with insufficient and adequate 25(OH) levels in early pregnancy
							Unadj Length at 1 month	54.8 (0.05)	54.2 (0.09)	54.8 (0.10)	55.1 (0.06)
Viljakainen,2010 9	3 (med)	Helsinki, Finland n=125 women recruited during last trimester (Oct-Dec). All Caucasian, non-smokers, primiparous	Cohort	Parental size, maternal wt gain in pregnancy, solar exposure, total intake of vitamin D and initial 25(OH)D conc.	First trimester (8-10 weeks) and 2 days post-partum. Mean of 2 values used to calculate “vitamin D status”	At 8-10 weeks = 41.0 (13.6) Postpartum = 45.1 (11.9) Overall mean= 44.8 (11.9) Overall median “vitamin D status” used to categorise group=42.6			25(OH)D below median (42.6 nmol/l)	25 (OH)D above median (42.6 nmol/l)	P (diff. between means)	Not given	Not given	No significant difference in offspring birth length or z-score birth length if maternal 25(OH)status below median compared to above (median=42.6 nmol/l) An inverse correlation was observed with postpartum 25(OH)D and birth length z-score (r= −0.261, p=0.013). This relationship was no longer significant after adjustment for confounders
							Unadj. Birth length (cm)		51.0 (1.9)	50.5 (1.8)	0.140
							Unadj. z-score birth length		0.14 (1.0)	−0.20 (0.96)	0.104
Dror, 2012 93	7 (low)	Oakland California n=120 women	Cross- sectional	Gestational age, maternal age, maternal BMI, maternal height, ethnicity, parity, GDM	Perinatal	75.5 (32.3)	Not given					−0.004 p=0.53	−0.009 (−0.022-0.004) p=0.18	No association seen between maternal serum 25(OH)D and offspring birth length

^*Measured 25(OH)D₃

^**Measured when infant was 1 month old