Congrats to the new little life.. Hope your gf's pregnancy is a smooth one with no morning sickness etc.
Let me see if I can help with anything based on my personal experience...
Pre-natal
Gynae: Dr Chia Yee Tien, The Ob and Gy Practice at Mount Elizabeth medical centre. She has more than a decade of gynae experience. First few visits I paid by per consultation about 100-200 plus excluding Oscar test and health supplements. Think until sometime near end of 2nd trimester, you may need to decide to sign up package until baby's delivery. It cost me around S$2k for normal delivery excluding hospital ward charges. I stayed in 2-bedder at mount e hospital natural birth with epidural and I think that cost me another S$4k excluding medisave deductions.
Post-natal
Confinement: if getting a confinement lady -S$2.5k -S$3k depending on exp and whether is it on cny period. Confinement food charges separately ~S$1.2k-S$2 depending on cost of tonics etc or who is cooking for you
Post-natal massage: optional but if gf wishes to do: S$500 onwards per package
Baby stuffs
Breast pump: Medela double pump (~S$700-S$800) depending on model and how many spare parts
Milk bottles: ~S$15-S$20 per bottle depending on brand and size
If your gf is planning to breastfeed, it is virtually cost-free. Perhaps just need to get her nursing tops, nursing bras, nursing dresses, nursing cover =~S$200-S$300
Clothings (for 1-3 months old) mittens, socks, rompers, t-shirts, swaddling cloth, washcloths= S$100- S$200 depending on brand and material
Beddings: baby pillow, bedsheet, baby cot, blanket, bumper = S$100- S$1,000 depending on what type of baby cot. If you are planning to have bb co-sleep with you, cost should be below S$100 depending on brand of blanket
Miscellaneous items: infant toys, night light, baby soothing music device, wall paper to decorate room, bath tub etc= $$$ depending on what you want to get.
Stroller: ~S$500-S$2k depending on brand
Diapering : newborn on average uses 8pcs of diapers everyday but after 3rd month bb uses less= S$50- S$100 per month (including wet wipes) depending on brand. I don't use wet wipe that often after my bb turned 6 months old. I bring her to the wash basin or bathroom and clean with water directly. It is much more hygienic, environmentally friendly and cost-saving. Buy in bulk can help you save money and sometimes they come with free delivery.
Milk and food: if not breastfeeding, milk powder cost ~S$70- S$200 per month depending on brand of milk powder. Food wise, only feed them purée food after 6 months of life and cost is negligible because they eat really very little. Milk is still their main source of nutrients etc
Insurance: life insurance and hospitalisation plan highly recommend to get
Sterilising and cleaning: bottle or vege washer, baby detergent, toiletries, steam steriliser ~S$200- S$300 depending on brand of steriliser. Bottle or vege washer and baby detergent can get very cheap at Chinatown market if you are not fussy with brand. Consumption should be 1 packet per month.
Vaccination: free for sgp baby for basic immunisation at polyclinics. Just do it at polyclinic, there is priority queue for babies and there is no difference in terms of the vaccination "drugs" for public vs private clinics. If you prefer private, I know some PDs charge as high as S$2k for a package which may include some jabs that are not really necessary.
My initial upfront cost from day 1 of pregnancy until my bb was 3 months old was above S$10k not including her jaundice treatment, medical cost. I did not hire a confinement lady, bb co-sleep with me, I got freebies from friends and relatives, baby shower presents etc.
If you guys are planning to get married legally, the baby bonus will surely help to offload the cost.
I'm sure I have missed out some items, but there are just too many to list out here.
In any case, just enjoy the pregnancy and celebrate the new life on the way!
Let me know if you wanna get some items brand new or preloved as I may have some for your consideration.