Answer
Usually, in the UK, no direct anaesthesia or pain relief is given to the baby during an abortion. Sometimes it is given in late-term abortions before 'feticide', where a lethal injection is used to stop your baby's heart.
There are different theories on when (and if) unborn babies can feel pain. Mostly revolving around stages of brain development.
Weeks on this page are all since LMP (last menstrual period) That is, gestational age rather than embryonic/fetal age – the baby's actual age since fertilisation (which is two weeks behind).
Late-term pregnancy:
A baby at 28 weeks reacts to an anaesthetic injection before surgery in the womb. (Note 1)
The question of fetal pain is highly debated. The Royal College of Obstetricians and Gynaecologists (RCOG) in 2010 held that it did not begin until 24 weeks. (Note 2) This was reviewed in 2022, and the review concludes 'To date, evidence indicates that the possibility of pain perception before 28 weeks of gestation is unlikely.'
However...
Early pregnancy:
One of the (2010) RCOG authors has since changed his mind:
'Overall, the evidence... points towards an immediate and unreflective pain experience... from as early as 12 weeks.' (Note 3)
Others suggest possibly around 7 to 8 weeks (Note 4). This link includes summary notes.
More pain?
Some even consider ' ...its immature physiology may well make it more sensitive to pain, not less: the body’s mechanisms for inhibiting pain and making it more bearable do not become active until after birth.' (Note 5)
How might you feel afterwards?
Why not be cautious.
If you are asking this question, it sounds like you care about your baby. Will you do all you can to protect them?
Notes
(1) A new study has shown that unborn babies undergoing an anaesthetic injection into their thigh before surgery, demonstrate changes in facial expression similar to newborn babies experiencing pain.
(2) Fetal Awareness:Review of Research and Recommendations for Practice, Published by Royal College of Obstetricians and Gynaecologists, March 2010
(3) Reconsidering fetal pain Journal of Medical Ethics (bmj.com) Stuart WG Derbyshire*, John C Bockmann. 2020. (*Pro-choice on abortion, and a leading expert on fetal pain)
(4) Fetal Pain in the First Trimester The Linacre Quarterly, Bridget Thill. December 2021.
(5) First Ache Feb 10, 2008, New York Times article. Interviewing fetal pain experts.