Non-pregnant Women Have a Lower Vitamin D than Pregnant Women After Gastric Bypass

Abstract

Objective: To compare the nutritional status of vitamin D, calcium, and serum concentrations of parathyroid hormone (PTH) between women undergoing Roux-en-Y gastric bypass (RYGB) who became pregnant and women who did not become pregnant during the same postoperative period, as well as the impact of these changes on maternal and child health.

Methods: This is a longitudinal and retrospective study of women who previously underwent RYGB, paired by age and preoperative body mass index (BMI), divided into two groups: group 1 (G1), comprising 79 women who did not become pregnant, and group 2 (G2), comprising 40 pregnant women assessed in the overall trimesters. Both groups were analyzed before surgery (T0) and in the same interval after surgery: less than or equal to 1 year (T1) or greater than 1 year (T2), with a 2-year period at the most. Serum concentrations of vitamin D, calcium, parathyroid hormone (PTH), and gestational and neonatal complications were investigated. Statistical analysis was performed by the Statistical Package for the Social Sciences 21.0 (p < 0.05).

Results: Despite the additional nutritional demands at pregnancy, women evaluated after 1 year of RYGB had the highest demands of vitamin D when compared with pregnant women in the second trimester(p = 0.04). Women who became pregnant within 1 year of bariatric surgery were more likely to develop a urinary tract infection which, in turn, was associated with vitamin D inadequacy (p = 0.02).In the same period, the concentrations of calcium in the second and third trimesters showed a strong correlation with the number of pregnancies (R = 0.8, p = 0.008, R = 0.8, p = 0.003) and deliveries (R = 0.7, p = 0.013, R = 0.8, p = 0.006) and its nutritional status in the first trimester also showed a strong correlation with the occurrence of small newborns for gestational age/large for gestational age (SGA/LGA) (R = 0.8, p = 0.007).

Conclusion: Since the highest vitamin D depletions occurred in G1 when compared with G2, the study suggests that a period of time for supplementation and its adjustments in post-bariatric pregnancy may be beneficial. It also encourages further investigation on the number of pregnancies/deliveries during prenatal care, due to vitamin D influence on the nutritional status of calcium, and it points out that changes in concentrations of this vitamin in pregnant women may lead to SGA/LGA newborns' births.

Keywords: Calcium; Pregnancy; Roux-en-Y gastric bypass; Vitamin D.