Chinese gender calculators, such as those found on Calcuworld, which purportedly determine a baby's sex before birth and even before conception based on an ancient Chinese gender chart, are unscientific and unreliable. Amniocentesis and obstetric ultrasonography are scientifically reliable procedures for prenatal sex discernment, according to ScienceDirect.
Calcuworld claims prospective parents can use the ancient Chinese pregnancy calendar to predict the sex of their expected infant based on the mother’s age and conception date. This website features a calculator that lets users input the respective values and get the predicted gender of the unborn child, though the website itself admits that the prediction cannot be as reliable as one obtained from medical examinations and ultrasounds.
Chinese Fortune Calendar has a similar gender calculator that supposedly can predict prenatal sex for not only actual but also future pregnancies based on mother's date of birth and month of conception. For example, according to this calendar, which extends through 2018, a woman born June 15, 1980, conceiving a baby on February 23, 2017, is predicted to have a girl.
Amniocentesis is an invasive procedure not entirely without risk of harm, says ScienceDirect, and the ultrasonic accuracy rate, estimated to be over 90 percent, depends on fetal age, sonographic precision, operator expertise and fetal posture.