The conception chart has its origins in 13th-century China. It purports to be able to tell a pregnant woman the gender of the fetus she is carrying. Its accuracy has not been confirmed by the scientific method. The fact that twins of different sexes are born lends question to its accuracy.
In astrology, a Natal chart is the map of sky at the date and time of birth. By using this Natal chart there is a way to plot the Conception chart. Conception chart is the map of sky at the date and time when that native was conceived. There are laws to calculate the pregnancy period using the phase of moon and the ascendant and the Moon's position in the Natal Chart.
A chart allegedly based on the Chinese conception chart, and having appeared in Mothering magazine, claims to predict the gender of the child based partly on the age of the mother at conception.