Effect of Maternal Age at Childbirth on Obesity in Postmenopausal Women: A Nationwide Population-Based Study in Korea

Abstract

The object of this study was to assess the obesity in postmenopausal women, according to age at childbirth.We analyzed the association between age at first childbirth, age at last childbirth, parity, and subject obesity status (general obesity; BMI >25 kg/m, nongeneral obesity; BMI ≤25 kg/m, abdominal obesity; waist circumference >85 cm, nonabdominal obesity; waist circumference ≤85 cm), using data from a nationwide population-based survey, the 2010 to 2012 Korean National Health and Nutrition Examination Survey. Data from a total of 4382 postmenopausal women were analyzed using multivariate regression analysis with complex survey design sampling. And, the subjects were subdivided into groups according to obesity or not. Age, smoking, alcohol consumption, exercise, education, income level, number of pregnancies, oral contraceptive uses, breast feeding experience were adjusted as the confounders.The prevalence of general obesity among Korean postmenopausal women was 37.08%. Women with general obesity and abdominal obesity were significantly younger at first childbirth compared with women with nongeneral obesity and no abdominal obesity (23.89 ± 0.1 vs. 23.22 ± 0.1, P <0.001). Age at first childbirth was inversely associated with obesity, while age at last childbirth was not associated with obesity or abdominal obesity. Women with a higher number of pregnancies were also more likely to have obesity and abdominal obesity. Age at first childbirth remained significantly associated with obesity, after adjusting for confounding factors.Obesity in postmenopausal women is associated with first childbirth at a young age, and higher parity. Further research is needed to clarify the association between obesity and reproductive characteristics.

FIGURE 1

The mean age at first and last childbirths according to obesity categories. The group with general obesity and abdominal obesity had a significantly lower age at first childbirth compared with those with nongeneral obesity without abdominal obesity. Nonobesity BMI: <25 kg/m²; obesity BMI: ≥25 kg/m². Nonabdominal obesity AC: <85 cm; abdominal obesity AC: ≥85 cm. BMI = body mass index, WC = waist circumference.

FIGURE 2

The mean parity according to obesity. A direct association is shown between parity and obesity, which is especially strong for abdominal obesity (P = 0.001). The prevalence of obesity was higher in women who had higher parity. Nonobesity BMI: <25 kg/m²; obesity BMI: ≥25 kg/m². Nonabdominal obesity AC: <85 cm; abdominal obesity AC: ≥85 cm. BMI = body mass index, WC = waist circumference.

FIGURE 3

The relationship between obesity and maternal age or parity. (A) The graph shows a gradual increase in the risk of general obesity with the higher quartile of parity and with the lower quartile of age at first childbirth, but not in the age at last childbirth. (B) The graph shows a gradual increase in the risk of abdominal obesity with the higher quartile of parity and with lower quartile of age at first childbirth, but not in the age at last childbirth. Last, age at last childbirth; first, age at first childbirth; 1, 1st qurtile; 2, 2nd quartile; 3, 3rd quartile; 4, 4th quartile.