Families may have an only child for a variety of reasons, including: personal preference, family planning, financial and emotional or physical health issues, desire to travel, stress in the family, educational advantages, late marriage, stability, focus, time constraints, fears over pregnancy, advanced age, illegitimate birth, infertility, divorce, and death of a sibling or parent. The premature death of one parent also contributed to a small percentage of marriages producing just one child until around the mid 20th century, not to mention the then rare occurrence of divorce.