Abortion.

"But it can't feel pain until the 3rd trimester."

One: whether someone can or can't feel pain isn't important and has no impact on the value of their life. Many drugs and pain killers make it that you can't feel pain, yet that doesn't and SHOULDN'T make it okay to kill you. 

Two: This is actually debatable, and let me tell you why.

Most women find out they're pregnant at 6 weeks at the next missed period (right after a period is the only time you can get pregnant). Most women take a few weeks to decide, or even to find a clinic and get an appointment.

With this said, most women abort at 8-14 weeks.

The topic of pain in fetuses in tricky. Some scientists say they don't feel pain until late second trimester or early third. Newer studies, however, claim otherwise.

Here is a paper conducted by Dr Bridget Thill (MD, MS) from December 2021: 

Current neuroscientific evidence indicates the possibility of fetal pain perception during the first trimester (<14 weeks gestation). Evidence for this conclusion is based on the following findings: (1) the neural pathways for pain perception via the cortical subplate are present as early as 12 weeks gestation, and via the thalamus as early as 7–8 weeks gestation; (2) the cortex is not necessary for pain to be experienced; (3) consciousness is mediated by subcortical structures, such as the thalamus and brainstem, which begin to develop during the first trimester; (4) the neurochemicals in utero do not cause fetal unconsciousness; and (5) the use of fetal analgesia suppresses the hormonal, physiologic, and behavioral responses to pain, avoiding the potential for both short- and long-term sequelae.

In conclusion, this doctor/scientist claimed (alongside many others) that fetuses can feel pain at 7-8 weeks via the thalamus and at 12 weeks via the cortex. So pain does occur during the first trimester at the time of the abortion. 

This does not mean we should kill it anyway but use anesthesia. It means it can feel pain like the rest of us, and should have the right to not be killed, like the rest of us.