I'll just add my two cents OP, so you have an idea of why antenatal care is so important.
In my first pregnancy, I felt completely healthy and well. I had a normal BMI, was 30 years old, fit and healthy, no family history of illness. I was having a completely straightforward pregnancy with no concerns. I didn't have symptoms of any kind.
At my 16 week midwife appointment my midwife identified that my bump was measuring ahead for my gestational age. I was sent for an additional growth scan which identified that my baby was measuring very large. That prompted a referral for a glucose tolerance test, which I failed spectacularly, and I was diagnosed with Gestational Diabetes. I ended up having to take metformin and insulin to control my blood sugar. I reiterate - I had NO symptoms of gestational diabetes of which I was aware; no thirst, no hyperglycaemia, no discomfort or physical awareness at all.
By the time I reached 38 weeks pregnant, I was having various forms of monitoring three times per week. A urine test at one of those appointments revealed that my kidneys were starting to fail as a result of the diabetes. Again - I had no symptoms and felt fine. I was advised to consider induction for my and my baby's sake, and he was born safely. I am well, and he is alive, because of the antenatal care I received.
You don't always know when something is wrong in a pregnancy. You don't always have symptoms. Much of what can lead to dangerous outcomes is only picked up on scans or blood tests.
You are an adult; you have the right to decline care if you don't want it. But make sure your choice is informed and that you understand that you're choosing risks which will not always be known to you, and which will not come with the benefit of obvious symptoms.