YAMFWOT, I am not equating the situation of homophobia with motherhood. I am saying that motherhood is a protected characteristic just as sexual orientation is, in both UK law and international human rights law. The situation for mothers (in terms of all manners of laws that have historically existed until recently about whether or not they could work, in what fields they could work, where they could go, who had a right to make decisions about their liberty etc. There are still women in institutions now in the UK who were put there in the fifties for being pregnant) is not entirely equivalent to being a mother, just as being gay is not entirely equivalent to being a person with autism. But all are protected characteristics.
Squizita, I am recurrent miscarrier and a mother. Of course there needs to be adequate research and medical care into reproductive health for women, and women with fertility issues are treated unequally, but miscarriage and infertility are not the same thing as being childless. Some childless women experience problems with infertility and some do not, just as some women with children do.
Both the state of being a childless woman and the state of being pregnant or a mother can be both choices and situations a person is forced into. The fact that motherhood is often not a choice is a major global rights issue. There are still many women in the UK who are forced into pregnancy and/or motherhood when they don't want that.
The situation with carers of elderly parents is one of a need for increased rights for carers of people who are sick and/or disabled. That is not a situation unique or massively over-represented among childless women compared to mothers.
The OP was very simple. She thought that childless women (not an individual childless woman) were being treated unfairly, and then compared that to her experiences of mothers. She also compared her experience to parents, but this thread has mainly been about comparing mothers and childless women. If we are asked who is being treated unfairly between two groups (not individuals) then we look for markers of collective power and disadvantage between the two groups.
Economic: who earns more per hour relative to their skills, experience and education. Mothers or childless women? Relative to their numbers in society, who is more likely to be living in poverty? Mothers or childless women? Who is more likely to be sacked because they do or do not have children?
Political: who is more likely to be under-represented in politics, the senior civil service, the legal profession and the police?
Cultural: out of the top films released in a year, are the collective lead female characters (Katniss Everdeen, Pepper Potts, Natasha Romanoff etc) likely to over or under represent the proportion of women who have children or those who do not? Are women who hold power in arts, music and the media likely to be over-representative of the numbers of mothers or the number of childless women? Who is more likely to have remain without adult company, and have their opportunities to engage in adult social experiences in general curtailed? Are there more social spaces where people in the company of children cannot enter or people not in the company of children?
Health: who is more or less likely to experience health problems, disability and illness as a consequence of their state - childless women or mothers?
If people honestly believe that childless women are, on balance, disadvantaged relative to mothers, then there should be a plan to restore that balance. The choice is then to reduce the advantages of mothers by taking money, resources, jobs, cultural focus, power and rights (maternity leave, childcare etc) away from mothers, or it is to increase the relative advantage of childless women by increasing their money, resources, jobs, cultural focus, power and rights relative to mothers.
If childless women are, on balance, advantaged relative to mothers, then they are not collectively being treated unfairly compared to mothers. There are situations where they may be treated unfairly as a consequence of being a woman where there childlessness is mentioned, just as many straight women are treated unfairly and aspects of their straightness is mentioned. But the causes of that are sexism, and the relative power of men. The cause is not that mothers or lesbians have too many rights or preferential treatment.