Cancer associated with pregnancy can be defined as disease diagnosed within pregnancy or within 1 year postpartum. While malignancies in women of reproductive age are relatively uncommon, they are, after accidents, the most common cause of death in women aged 20–39 in the USA. It is apparent that the diagnosis of cancer is made less frequently in pregnant women than in age-matched controls. The potential reasons for the reduction of cancer incidence in pregnancy include:

1. ▪ pregnant women may be generally more healthy (the so called ‘healthy pregnant woman effect’)

2. ▪ women with a known cancer may not become pregnant or continue with a pregnancy

3. ▪ the symptoms from the malignancy may be ascribed to pregnancy, so delaying diagnostic and screening tests until after the pregnancy and hence delaying diagnosis.

Overall, in the UK, women are delaying childbirth, which has led to an increase in the proportion of older mothers. In 1971, the average maternal age was 26.2 years, which had risen to 29 years by 1999 (Figure 1.1). As a result, the diagnosis of cancer is becoming more common during pregnancy and is likely to increase further as the trend for delaying childbirth continues.

Data from the most recent Confidential Enquiry into Maternal Deaths suggest that there has been a significant increase in the number of maternal deaths in the UK due to cancer. During the period 2003—05, 82 women died from cancer compared with 28 in 2000—02.