According to this link, about 8% of new mothers will get post natal depression. http://sg.theasianparent.com/postnatal_depression_in_singapore/ There is a higher chance of getting post natal depression if you are in a stressful situation (i.e. conflicts with in-laws, moving house, financial difficulty) and/or you have a poor relationship with the baby's dad. https://www.nlm.nih.gov/medlineplus/ency/article/007215.htm
Raising a baby is very stressed. Women undergo hormones changes during pregnancy and after delivery. Thus, if you feel something is not right, e.g. crying easily, feel anxious all the times, please talk to your family immediately and seek professional counselor's help. http://www.singhealth.com.sg/PatientCare/ConditionsAndTreatments/Pages/Postnatal-Depression.aspx
I hope your question means the the number of women suffering from post natal depression. According to research about 10-15% of asians suffer from post natal depression which is the lowest worldwide. Also there are many factors which may lead to post natal depression like previous depression histroy, lack of sleep, breastfeeding, etc. I hope this answers your question
thanks