In the final of the sheets on antidepressant / anti anxiety SSRIs is fluoxetine. It is often looked on as the least compatible with breastfeeding because of its long half life and greater passage into milk. However, it is often used in pregnancy because there are a significant number of studies https://www.medicinesinpregnancy.org/Medicine–pregnancy/Fluoxetine/. What is perhaps less well known is that if a mother has taken it throughout pregnancy the baby MAY be very drowsy in the first few days after delivery as it withdraws from the higher levels achieved through placental transfer.
My recommendation for any mother taking fluoxetine during pregnancy and wishing to breastfeed is to learn hand expression in preparation https://www.unicef.org.uk/babyfriendly/baby-friendly-resources/breastfeeding-resources/hand-expression-video/ and to maybe discuss antenatal expression of colostrum with the midwife, just in case the baby is sleepy and taking time to latch effectively. Colostrum can raise blood sugars in very small amounts. (This is really helpful info for the red flags of low sugar and in my opinion explains everything well https://www.guysandstthomas.nhs.uk/resources/patient-information/maternity/protecting-your-baby-from-low-blood-glucose.pdf)
So you can breastfeed after delivery if you have taken fluoxetine but you may need a little help and support. Seek this antenatally so you are well prepared.
I would also add that if fluoxetine has been the SSRI that you have used and found effective in the past, then that would make it the first choice in breastfeeding. Some babies are colicky, some are drowsy, some vomit, some have loose diarrhoea – but we cant tell in advance.
I remember the very first study I looked at on fluoxetine some 25 or more years ago that the mother and the baby’s paediatrician thought the baby hadnt changed behaviour when exposed to fluoxetine via his mother’s breastmilk. The baby’s father (also a paediatrician) perceived it as more irritable and on that anecdotal basis back then it was said that fluoxetine made babies irritable. I cant find the report any more but if we had been able to see into the family unit we may have seen a dad trying to help his partner whilst working and feeling stressed himself. Who knows?
I hope this information is useful to anyone taking fluoxetine whilst breastfeeding