Since I study this and am an active part of the battle for sex worker rights and helping people understand the industry better, I think I can probably help with adding a little perspective.
Firstly, there is simply not information to back up Dr. Pinsky's claim. In fact, his claim is one that is extremely difficult to test, at this time, and it is unlikely to get enough data to make any such claim with any expectation of being remotely accurate. This is because most sex workers are not open about their sex work and most abuse victims are also averse to discussing their abuse. I'll discuss more about this in a moment.
I appreciate the articles that Alain posted, but they actually show a different correlation - that those who are already OK with discussing their experience with sexual abuse are more likely to discuss working in the sex trade. This, is unlikely to give us much information on a possible pattern within the sex industry, though, as there are too many variables that exist within both groups, those who have suffered sex abuse and those who have sold a sexual service, to paint us a very good picture of what we might see if we examined the histories of sex workers closer.
I run an organization, The Eastern Washington Sex Workers Outreach Project that has multiple goals for addressing issues that sex workers face. One of the functions is to fight for the rights that sex workers need to have a safer environment. Another purpose of the organization is to educate others about the realities of the sex industry (not the Hollywood version, not the anti-sex and anti-porn versions and not the wonderful sex world version, either, we want to educate a balanced version). We also try to address one of the common issues that sex workers face in that they are more likely to experience domestic violence and are less likely to be able to obtain help or resources that can help them escape it. Lastly, something that I provide on the side, which isn't a part of the umbrella SWOP organization, is peer counseling for fellow sex workers.
This position of being a sex worker and launching my own non profit organization designed to help them gives me a unique opportunity to examine questions such as this. Here's what I have found:
Correlations between histories of sex work are much like other types of correlations that we find in other types of work. For example, just because there may be a higher rate of the abuse of controlled substances amongst doctors doesn't mean that we should treat the profession of a doctor differently or with the expectation that a doctor is likely a drug user.
Sex workers who have a history of being sexually abused don't seem to number higher, per capita, than other women who I have counseled, in the past, who have suffered from being sexually abused. In other words, when I was a peer counselor for Domestic Violence Services in Oregon, the rate at which I counseled women who needed my help as a peer counselor who mentioned sexual abuse does not seem to be lower than the amount of sex workers who seek my help now who have experienced the same. This is a very small sample of people, though, and the subgroups are specific to the organizations within which I was functioning. Still, it is the best data that I have right now and I do think it is interesting and worth noting to dispel certain ideas that people have.
If it is ever found to be the case that sex workers have a more common history of being sexually abused, this should not play a role in creating further prejudices against the industry. It is not the fault of the industry that this has happened and there is no evidence that sex work, itself, is somehow a negative consequence of such abuse. The reason the idea is reinforced that sex workers are more commonly victims is because it provokes emotions in people that often results in demonizing the industry, itself. However, there is nothing to show that this is either a useful or practical response to such information, were it even true.
Most sex workers, regardless of history, seem to enjoy their work and many see it as empowering. One of the methods of treating victims of sexual abuse is to teach them to be empowered by their individual sexuality. If sex work is empowering to many women, it is perhaps the case that it is not an unhealthy way to deal with their experience. Of course, there is not really enough data to support or deny this hypothesis. I hope that there is room for research for this in the future.
Now, on to some other relevant information that is important for you to consider. Abuse victims, especially sexual abuse victims, in our culture, have a difficult time discussing their experiences with others. It is very common for abuse victims to avoid the subject, if at all possible and those who speak out often have difficulty discussing the details. Many counselors try to allow individuals to work within their capacity to deal with their problems, so there is little incentive to pull that information out of them (assuming the counselor is up-to-date on their psychology - in the past, some counselors would pry, and there is evidence that they either made the situation worse or accidentally recreated experiences).
When dealing with sex workers, many of them are very scared. In fact, the more legally and socially risky the job is, the less likely the worker is to be open about what they do for a living. This makes getting any information from them about their past or their life outside of their work extremely difficult. I know, I've tried. Sometimes, this problem is even more complicated when others are involved with the sex worker's business. If there is a pimp involved, or a boyfriend or girlfriend or even a contract holder, that will change how the sex worker interacts with others and can make it even more dangerous for them to disclose information. Here are some examples of that danger:
In one of my early webcam model contracts, I met a mathematician who was contracted to the same company, who I became good acquaintances with. We often talked about science and math. My contract holder, at the time, ended up in an argument with her and she quit. In the process, though, the contract holder responded to her by threatening to tell the University she worked at about her work as an adult webcam model. She worked at a University that would certainly have fired her, if that had happened. This threat kept her from doing anything about it when the contract holder misbehaved.
Recently, I made an accidental contact with an escort in Idaho. The girl's boyfriend was interested in a cat that I was giving away. When the conversation went into further detail about the agency she was working for, a person claiming to be her boyfriend took her phone and sent me a text telling me never to text her again.
While I encounter many sex workers who are in support of or in need of help from my organization, most of them are unwilling to come out as sex workers. As a result, I have a great network of people, but my meetings tend to have very few attendees. out of dozens of contacts, just over a handful are willing to come to a meeting and discuss sex work and how to deal with our current social environment to improve our general status.
These factors, combined, I think, makes even testing a claim about sex workers and past sexual abuse a pretty difficult task. Even I don't think I have sufficient data to support one position or another.
Until we have a better social attitude about sex work, I am pretty sure it is unlikely we will uncover enough information to see if there is any correlation or not.