It’s all about their neck and spine strength. Some babies seem to be okay in the pram part but you need to look at their posture as their head can tilt into their neck a bit + can put pressure on their lower back - which gets overlooked. Which is why they say babies should lay flat and at 6 months/ when they’re able to sit up and support their neck, they can change to pram. I know the carry cot part is bulky but I say assess your baby and do what’s best for them.
Thanks both! Her neck strength is getting better but I think I’ll stick with the carrycot a bit longer
I put my girl in the pushchair at around 13/14 weeks.. but mine does lay flat and is suitable from birth. She has it reclined but not fully now at 17 weeks. It is about how they can sit and whether they can support themselves.