This is the most viewed news in Hong Kong today.
Hospitals in China can refuse to take in patients if they are found to have AIDS, so some pregnant women think HK is their best bet to deliver the babies safely. Moreover, these Mainland parents usually abandon the babies soon after birth hoping that the HK government will take care of the AIDS babies.
In fact, Mainland parents frequently ditch the babies as soon as they find out there is some congenital problems with the newborn. Babies with AIDS, congenital heart problems, mental disability, or Down syndrome are frequent findings amongst those abandoned by the Mainlanders in Hong Kong.
Babies born in Hong Kong can get immediate residency status, which means that they can enjoy all medical and social benefits, as well as go to school in HK. This has motivated a lot of women from the Mainland to travel across the HK-China border when the baby is about to pop out. Despite of measures imposed by the HK government (such as requirement of a hefty deposit prior to hospital booking and at least one pre-natal check performed in HK), babies borne to Mainland parents make up a significant portion of births in HK (28% in 2006 and 2007). The trick is to go to HK as a tourist (by wearing lots of loose clothing to disguise the belly) then wait until the last minute when the water is broken, call the ambulance and have the baby delivered in the A&E.
Of course this doesn't sit too well with the HKers. But there is absolutely nothing they can do about it as HK is officially part of China now. In fact, there are plans to make it even easier for Shenzhen residents to go to Hong Kong. Good thing is that more HKers can speak fluent Mandarin now; bad thing is that the discrimination against the Mainlanders is just as bad as the pre-1997 era, if not worse. (the following link is a thread on one of the most popular on-line forums in HK)