I am reading an article about the effects of mother's blood pressure on the gender of the child. the following sentence was in the context that I have no idea what the author means:
Those who had a female child had an average systolic blood pressure of 103.3mmHg before pregnancy, while for mothers of males the figure was 106, about 2.6 per cent higher. Fundamental biology means there is generally a 50/50 split in the sex ratio, although in humans there is a slight bias towards males.
Please let me know what this part means: there is a slight bias towards males