Effect of vitamin D status on clinical pregnancy rates following in vitro fertilization

Kimberley Garbedian; Miranda Boggild; Joel Moody; Kimberly E. Liu

doi:10.9778/cmajo.20120032

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Table 1: Characteristics of 173 women undergoing in vitro fertilization, by vitamin D status

Characteristic	Vitamin D status, mean (± SD)*
Characteristic	Insufficient or deficient n = 95	Sufficient n = 78	p value†
25-Hydroxy-vitamin D, nmol/L	54.5 ± 14.0	95.5 ± 17.8	< 0.001
Age, yr	34.6 ± 4.0	34.4 ± 3.9	0.8
Ethnic background, no. (%)			0.3
White	56 (58.9)	58 (74.4)
Black	3 (3.2)	1 (1.3)
Other	36 (37.9)	19 (24.4)
Body mass index	24.8 ± 4.7	23.3 ± 3.8	0.02
Gravidity	0.8 ± 1.1	0.9 ± 1.3	0.6
Parity	0.2 ± 0.5	0.3 ± 0.6	0.5
Duration of infertility, mo	20.7 ± 15.1	17.5 ± 12.3	0.1
Follicle-stimulating hormone, baseline, IU/L	6.4 ± 1.9	6.8 ± 2.3	0.9
Antral follicle count, baseline, no. of follicles	15.9 ± 8.4	17.7 ± 10.3	0.2
Previous IVF cycles, no.	0.7 ± 1.0	0.6 ± 1.0	0.4
Season in which IVF cycle was performed, no. (%) of patients			0.8
Spring	50 (52.6)	41 (52.6)
Summer	31 (32.6)	28 (35.9)
Fall	14 (14.7)	9 (11.5)

Note: IVF = in vitro fertilization, SD = standard deviation. *Unless otherwise stated. †χ² (categorical) and Student t or Mann–Whitney U (continuous) test; statistically significant, p < 0.05.

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Table 2: In vitro fertilization cycle parameters for 173 women, by vitamin D status

Characteristic	Vitamin D status, no. (%) or mean ± SD		p value*
Characteristic	Insufficient or deficient n = 95	Sufficient n = 78	p value*
IVF protocol, no. (%)			0.08
Long	29 (30.5)	34 (43.6)
Antagonist	64 (67.4)	40 (51.3)
Flare	2 (2.1)	4 (5.1)
Day of hCG injection	12.1 ± 1.3	11.9 ± 1.4	0.4
Gonadotropin dose, IU	2602.8 ± 1287.3	2547.1 ± 1330.3	0.8
Follicle diameter > 14 mm, no.	11.9 ± 6.5	11.7 ± 5.8	0.8
Estradiol level on the day of hCG administration, pmol/L	8556.7 ± 6187.3	9776.15 ± 5902.6	0.2
Endometrial thickness on the day of hCG administration, cm	1.0 ± 1.6	1.0 ± 0.2	0.5
Oocytes retrieved, no.	12.6 ± 7.4	12.7 ± 6.6	0.9
Intracytoplasmic sperm injection, no. (%)	74 (77.9)	63 (80.8)	0.4
Embryos transferred, no.	1.8 ± 1.0	1.8 ± 0.9	0.9
Day of embryo transfer, no. (%)
Day 3	31 (32.6)	19 (24.4)	0.2
Day 5	56 (58.9)	56 (71.8)	0.054.00
Implantation rate, %	25.6	34.5	0.6
Clinical pregnancy rate, per cycle start, %	34.7	52.5	< 0.001
Clinical pregnancy rate, per embryo transfer, %	37.9	54.7	< 0.001

Note: hCG = human chorionic gonadotropin, SD = standard deviation. *χ² (categorical) and Students t or Mann–Whitney U (continuous) test; statistically significant, p < 0.05. †Follicle-stimulating hormone or human menopausal gonadotropin, depending on protocol.

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Table 3: Predictors of clinical pregnancy among 173 women undergoing in vitro fertilization

Variable	Crude OR (95% CI)	p value	Adjusted OR (95% CI)*	p value†
Age, yr	0.96 (0.89–1.04)	0.3	0.98 (0.90–1.07)	0.7
Body mass index	0.92 (0.86–1.00)	0.05	0.94 (0.87–1.01)	0.1
Day 5 embryos transferred (v. day 3)	1.50 (0.81–2.90)	0.2	1.28 (0.61–2.77)	0.5
25-Hydroxy-vitamin D, mmol/L	1.02 (1.00–1.03)	0.2	1.01 (1.00–1.03)	0.05

Note: CI = confidence interval, OR = odds ratio. *Analyses adjusted for age, BMI, number of day 5 embryos transferred and 25 OH-D level. †Statistically significant, p < 0.05.