BMI , body mass index; NS , not significant
a Group 1 comprises women who had spontaneous pregnancy in the last year.
b Group 2 comprises women who did not have spontaneous pregnancy in the last year but were willing to become pregnant.
c Represents participants’ age when they started attempting to conceive.
d Minorities included the Mongol nationality, Hui nationality, and Zang nationality.
e Restricted to radioactive and toxic substances.
f Included those who never smoked and used to smoke.
g Included those who never drank and used to drink.
h Represents the duration of cohabitation when couples started attempting to conceive.
iIncluded a history of stillbirth, induced labor, spontaneous abortion, and ectopic pregnancy.