"Sex selection abounded in China’s ultrasound rooms and abortion clinics during the 1980s and ’90s..."

"... but laws and regulations enacted since 2001 have forbidden hospitals from carrying out the procedure. Unfortunately, this has led to the emergence of a network of so-called black clinics: underground establishments that offer illegal sex screening and abortions, and are usually operated by unqualified personnel. When preimplantation genetic diagnosis technology — a way of profiling the genes of an embryo before implantation in the womb — was first used in Chinese clinics in 1999, some of these customers then began appearing at underground IVF clinics, too. In the vast majority of cases, couples undergo illegal sex screening because they want to give birth to a boy, not a girl. Chinese society has historically favored sons over daughters for a number of reasons, particularly the notion that only sons can continue the family line. Although this cultural preference for boys harms society as a whole, couples who opt for illegal sex screening never seem to remember that many of their hoped-for baby boys will one day struggle to find romantic partners, thanks to their parents’ contribution to the country’s skewed sex ratio."

From "Chinese Couples Want Boys — Trust Me, I’m a Fertility Doctor/Too many parents-to-be come to me asking about illegal sex screening, but that’s just the tip of the iceberg" (Sixth Tone).