Maternal and neonatal vitamin-D status in twin versus singleton pregnancies

There is a paucity of information on vitamin D status of women with twin pregnancy and their newborns. This case-control study compared maternal and neonatal vitamin-D status in twin versus singleton pregnancies.

Subjects included 50 women with twin pregnancy delivering at >28 weeks and 50 gestational-age-matched women with singleton pregnancy delivering during the same period. Maternal and neonatal serum 25-hydroxy vitamin D [25(OH)D] was compared between the two groups using the independent Student's t-test on log values. Serum albumin-adjusted calcium, inorganic phosphate, and intact parathormone levels were also compared.

Maternal vitamin-D deficiency (VDD; serum 25(OH)D < 30 nmol/L) was present in 90% of twin and 88% of singleton pregnancies. The prevalence of neonatal VDD was 89% in twin and 74% in singleton pregnancies (P = 0.03). Maternal serum 25(OH)D was lower in the twin group as compared to the singleton group (14.3 ± 10.47 vs 18.5 ± 12.36 nmol/L; P = 0.02). Mean serum calcium, intact parathormone, and inorganic phosphate were comparable between the women in the two groups. Maternal and neonatal 25(OH)D showed positive correlation in the two groups (P < 0.001). Mean cord blood 25(OH)D was significantly lower in the twins than in singleton newborns (14.8 ± 12.63 vs 22.6 ± 16.68 nmol/L; P = 0.002). The difference persisted even after adjustment for birthweights and maternal serum 25(OH)D. Mean serum calcium was significantly lower in the twins.

Twin newborns and their mothers have higher VDD as compared to singleton newborns and their mothers in the VDD population.