The graph shows the levels of three hormones, oestrogen, progesterone and human chorionic gonadotrophin (HCG), measured in the blood of a woman during her pregnancy - HSC - SSCE Biology - Question 12 - 2021 - Paper 1

From the graph, it can be inferred that birth occurred around week 36 due to the significant drop in HCG levels observed at that time. This decrease in HCG, which is crucial for sustaining early pregnancy, indicates that the pregnancy has reached its term. Additionally, the levels of progesterone appear to decline after this point, further supporting the inference that birth took place around week 36.