Maternity care calendar wheel. Improved obstetric wheel developed in British Columbia

Gestational calendar "wheels" are not well designed for routine prenatal care or for presenting the uncertainties of predicting date of delivery.

To design and pilot-test a new gestational calendar wheel that predicts the range of normal due dates in a way that reflects the biological realities of pregnancy. The calendar has prompts that could facilitate provision of antenatal care, support prenatal education, and guide the timing of induction for pregnancies past their due dates.

The calendar sets out the key issues to be addressed with patients during pregnancy. It is designed to be photocopied while set to patients' dates: patients keep one copy; another is placed in their charts. The probability of delivering on a given date is presented graphically and as a percentage likelihood of giving birth during specified intervals. Twelve practising physicians, 12 residents, and 10 pregnant women pilot-tested and evaluated the wheel. Their responses were favourable.

The Maternity Care Calendar wheel is a substantial advance on existing obstetric calendar wheels. It incorporates evidence-based information that should facilitate prenatal care, promote prenatal education, and foster realistic expectations about the likely timing of delivery. Early in the pregnancy, it can help establish the timing of induction for pregnancies past their due dates. Further testing of the calendar's effectiveness in improving patient outcomes is needed.