Comparison of the maternal characteristics of the women who have been included versus those who have been excluded at the 21 years post-partum.

<p>* <i>P</i> indicates the significance level of the difference by characteristics of women who have been included in the analyses vs. women who were no included in the analysis. We used an F test for a continuous data and a chi-squared test for categorical data. Missing category was not considered in the significance test.