Influence of number of pregnancies and total breast-feeding time on bone mineral density

To analyze how the number of pregnancies and total breast-feeding time influence bone mineral density.

50 healthy women aged 35 to 40 years were studied. Weight, height, number of term pregnancies, time since last pregnancy and breast-feeding time were analyzed. They were divided in three groups as follows: I: nulligravidas; II: with term pregnancies, but no breast-feeding; III: with term pregnancies, with breast-feeding. Bone absorptiometry was done on all, at lumbar column and femur. The WHO criteria were used to define osteopenia and osteoporosis. Comparison among the groups was done with Student's t-test for independent samples, and simple regression analysis was done for number of gestations, total breast-feeding time, time since last birth, and T-score at lumbar column and femur.

The women were divided as follows: 15 in group I, 15 in group II, and 20 in group III. The average age was 37.7 +/- 1.5 years. No differences were found among the three groups in analyzed variables, when comparing bone mineral density, T- and Z-scores in L1-L4 average, femoral neck, trochanter, and Ward's triangle. There was no correlation among the number of gestations, total breast-feeding time, time since last birth, or T-scores at lumbar column and femur.

The number of pregnancies and breast-feeding time do not affect bone mineral density.