Child negelect to an unborn child

So I have a sister , her husband welds so he can afford to take care of her since she’s a sahm but he acts like he can’t take her to dr visits to track how her unborn baby put of pocket it’s irresponsible on both of their part and I find it neglectful and he’s way too controlling so I don’t know if she’s afraid to speak up for herself and demand him to take her to bi weekly dr visits as she has became a diabetic with her first pregnancy, I just wanna know your opinion of yall consider this child neglect I think from what my mom knows she has only been to an ultrasound appointment. What can I do ? I care about my sister and my unborn niece .