Question: after how long can an foetus be recognised to be male or female

Cheryl Andisi answered on 20 Jan 2017:

@abpb279
sex determination in an embryo happens immediately after fertilisation. the default sex is female, and being male will only occur if a y chromosome containing sperm fuses with the egg. as you can imagine, immediately after fertilisation there us only on cell that needs tk develop to a whole organism and the first step usually invoves very rapid mitosis to produce a mass of cells known as the morula. at this level, a male or female fetus cannot be differentiated. several other steps follow that ensure this mass of cells is ordered to start the formation of the organs, with the nervous system being first to form. in fetuses that have the y chromosome, the signal to start forming male characteristics come from between 6-8 weeks. these include formation of the testes that will release hormones to supress female chacteristics. the external reproductive organs to define males can however not be seen on an ultrasound untill about 20 weeks. in cases where genetic screening can be done, sex determination can be done immediately after fertilisation