Best cashback card for upcoming big expenses?

When talking about credit cards
Few things you need to first work out

1. Spend amount (applicable to cashback limits
2. Method of payment (online, paywave)
3. Category (eligible/ineligible)

Then you can get a fair answer.
Optimize your highest cashback cards first within the cashback limit
The rest then put in unlimited cashback cards.

Congrats on the pregnancy! Any reason why cashback is preferred to miles? Those with high % rebate have a cashback cap, which make them unsuitable for big expenses like you mentioned.

For hospital bills, Amex rewards points. In particular, with the Amex Krisflyer Blue, you will also obtain up to 13,300 KrisFlyer miles (worth $266) and $200 statement credit if you sign up using this link and spend more than $3000 in the first three months.​​​ The card also doesn't have a cap to maximum number of miles earned, so I think it would be one of the best options to consider.

If you are buying items online such as on Shopee, the Citi Rewards MasterCard is my go-to card which I recommend. It provides you with 4 miles per dollar, which is the same as an 8% discount (valuing 1 mile at 2 cents) in majority of the online stores. You can shop on Shopee, subscribe to Netflix or Spotify, pay for Telco bills and earn the rewards.

These miles have a validity of five years, so you will have sufficient time to redeem them. In just a year, I have already managed to get enough miles through my credit cards to redeem a business class round trip to Japan!

To add to the 4 miles per dollar, you can obtain 30,000 Citi ThankYou points (equivalent to $240) when you sign up using this link and spend $3000 in the first 3 months!

If you are focused on Cashback, for offline spending, you can consider the Citi Cashback+ Card (4.5% for first 3 months, 1.6% thereafter, which has no min spend) or Citi Cashback Card (8% cashback, min. $800 spending) specifically for months with high spend.

Hope this helps!​​​