An observational study on Ca supplementation and dietary intake during pregnancy on low birth weight and small for gestational age.

OBJECTIVE: To evaluate the effects of dietary Ca intake and Ca supplementation during pregnancy on low birth weight (LBW) and small for gestational age (SGA) infants. DESIGN: A birth cohort study was conducted in 2010-2012 at the Gansu Provincial Maternity and Child Care Hospital in Lanzhou, China. SETTING: A birth cohort study. PARTICIPANTS: Totally, 9595 pregnant women who came to the hospital for delivery at 20 weeks of gestation or more, and who were 18 years of age or older. RESULTS: Compared with non-users, Ca supplement users had a reduced risk of LBW infants (OR = 0·77, 95 % CI: 0·63, 0·95) and a reduced risk of nulliparous women giving birth to LBW infants (OR = 0·75, 95 % CI: 0·58, 0·98) (P < 0·05). More specifically, both the use of Ca supplement before conception and during pregnancy (OR = 0·44, 95 % CI: 0·19, 0·99) and during pregnancy only (OR = 0·80, 95 % CI: 0·65, 0·99) had the main effect of reducing risk of nulliparous women giving birth to LBW infants (P < 0·05). There was no association between Ca supplementation and SGA (OR = 0·87, 95 % CI: 0·75, 1·01) (P > 0·05). However, higher dietary Ca intake during pregnancy decreases the risk of both LBW (quartile 2: OR = 0·72, 95 % CI: 0·55, 0·94; quartile 3: OR = 0·68, 95 % CI: 0·50, 0·62) and SGA infants (quartile 2: OR = 0·77, 95 % CI: 0·63, 0·95; quartile 3: OR = 0·71, 95 % CI: 0·57, 0·88, quartile 4: OR = 0·71, 95 % CI: 0·57, 0·88) (P < 0·05). CONCLUSIONS: Ca supplementation and adequate dietary intake of Ca during pregnancy are associated with a decreased risk of LBW infants born to nulliparous women.