From the Heidelblog:
Please notice again how archaic it seems even to refer to the two sexes rather than to speak of gender, when it is patent nonsense to use them as synonyms. Sex is a biological category. Gender is a grammatical category. Sex refers to biology which is fixed in almost every case. Gender refers grammar which is relatively arbitrary and assigned. Once we conceded this confusion we opened the door for people to talk rubbish about “assigning gender” at birth. Physicians and midwives are not God. They assign nothing.