Gingerkittykat it's very true that the pregnant woman could very well be 22 stone for all anyone simply reading an article knows. It's very likely indeed she does all her own personal care - generally someone with moderate learning disabilities and no physical disabilities will do all their own personal care.
That's the thing, as thankfully is now established on this thread - comparisons to a 9 year old don't work on any level. Though tbh most 9 year olds can also wash, shower, hairwash and dress themselves.
She will have been having periods for at least 6 or 7 years so will be likely to manage them herself. They may be very irregular indeed due to weight and medication.
Of course she might be 6 stone and clearly showing from 12 weeks, she may have regular periods and no sense of personal privacy and need her mum's help with hygiene, but neither case is a forgone conclusion.
The people of both sexes I work with with this level of disability do go out alone, use public transport alone, have mobile phones and shower unsupervised. They are adults and have the right to live adult lives as far as possible.
They come home to a 24/7 staffed supported living facility and couldn't manage paying bills, anything buerocratic, completely independent household management or in most cases to manage their own medical issues. They need help resolving arguments and frequent reminders to shower, do their laundry, put plates in the dishwasher etc like teens. They live a lot like teens but a mental age assessment would put all of them below double figures.
They've lived longer than 9 years though so had 3 times as long to learn and practice certain self care and independence skills.
Some of them have no interest in a relationship but several of them are in committed relationships with peers and others want to be.
There really isn't enough information to make much of a judgement at all. In some cases someone with moderate learning disabilities can be supported to parent if they have a strong, supportive network of family and care workers and social workers. I know of two women with moderate learning disabilities living together in a 24/7 staffed mother and baby flat bringing up their children with significant support.
I suspect that in this case the mental health of the mother makes this impossible, and the background to pregnancy and wider family may complicate things further.