Introduction We examined parity and age among women seeking an abortion in Mexico City’s public first-trimester abortion programme, Interrupcion Legal de Embarazo (ILE). We hypothesised that younger women, especially students, used abortion to prevent first births while older women used abortion to limit births. Methods We used clinical data from a sample of 47 462 women who had an abortion between 2007 and 2016 and classified them as nulliparous or parous according to previous births prior to the abortion. We used logistic regression to identify sociodemographic and clinical factors associated with using abortion to prevent a first birth (nulliparous) versus limiting births (parous) and calculated absolute multivariable predicted probabilities. Results Overall, 41% of abortions were in nulliparous women seeking to prevent a first birth, and 59% were in women who already had one or more children. The adjusted probability of using abortion to prevent a first birth was 80.4% (95% CI 78.3 to 82.4) for women aged 12–17 years and 54.3% (95% CI 51.6 to 57.0) for women aged 18–24 years. Adolescents (aged 12–17 years) who were employed or students had nearly 90% adjusted probability of using abortion to prevent a first birth (employed 87.8%, 95% CI 82.9 to 92.8; students 88.5%, 95% CI 82.9 to 94.1). At all ages, employed women and students had higher probabilities of using abortion to prevent a first birth compared with unemployed women and women who work in the home. Conclusion Legal first-trimester abortion services in Mexico can help prevent first births in adolescents, especially students. No data are available. The study data were collected under a Data Use Agreement with SEDESA (Secretaria de Salud de la Cuidad de Mexico) which does not permit data sharing.

中文翻译：

---

在墨西哥城的公共堕胎计划中预防青少年首次生育

介绍 我们在墨西哥城的公共孕早期堕胎计划 Interrupcion Legal de Embarazo (ILE) 中检查了寻求堕胎的妇女的胎次和年龄。我们假设年轻女性，尤其是学生，使用堕胎来防止第一胎，而老年女性则使用堕胎来限制生育。方法 我们使用来自 2007 年至 2016 年间流产的 47 462 名妇女样本的临床数据，并根据流产前的先前生育情况将她们归类为未产妇或经产妇。我们使用逻辑回归来确定与使用流产预防第一胎（未产）与限制生育（经产）相关的社会人口统计学和临床​​因素，并计算绝对多变量预测概率。结果 总体而言，41% 的流产发生在寻求预防第一胎的未生育妇女中，59% 的女性已经有了一个或多个孩子。12-17 岁女性和 18-24 岁女性使用堕胎预防第一胎的调整后概率为 80.4%（95% CI 78.3 至 82.4）和 54.3%（95% CI 51.6 至 57.0）。受雇或学生的青少年（12-17 岁）使用堕胎预防第一胎的调整概率接近 90%（受雇为 87.8%，95% CI 82.9 至 92.8；学生 88.5%，95% CI 82.9 至 94.1） . 在所有年龄段，与失业妇女和在家工作的妇女相比，就业妇女和学生使用堕胎来防止第一胎的可能性更高。结论 墨西哥合法的孕早期堕胎服务有助于预防青少年，尤其是学生的头胎。没有可用数据。