Yes, he is using them for political gain, and doing so is vile.
But so is denying the reality of the gender-based violence that the majority of women migrating from Central America experience on their jorney - and the nightmare that these women feel they have to take birth control prior to the start of the journey to avoid the physical consequences of what they view as inevitable: rape on the journey north.
In addition to the risks of extortion, kidnapping, and violence that migrants face, migrant women are also vulnerable to sexual and gender-based violence, including rape and sexual assault. Women experience sexual violence and forced disappearances often near the border. According to Amnesty International, 60% of migrant women and girls are raped while migrating, while other data indicate that 80% of women experience rape and sexual assault during the migration process.
Given the frequency of sexual and gender-based violence, many migrant women take contraceptives before migrating to avoid the risk of pregnancy from rape by armed criminal groups, locals, or their smugglers.
https://unu.edu/publications/articles/fleeing-to-mexico-for-safety-the-perilous-journey-for-migrant-women.html
Health professionals report that as many as six in ten migrant women and girls are raped on the journey. And activists repeatedly raise concerns that abducted women and girls are vulnerable to trafficking.
https://www.amnestyusa.org/most-dangerous-journey-what-central-american-migrants-face-when-they-try-to-cross-the-border/