What causes an overdue pregnancy?

Due dates are estimates based on menstrual dates and, when available, ultrasound measurements. A longer or irregular menstrual cycle, uncertain dates or later ovulation can shift the estimate. Some pregnancies also naturally last longer despite accurate dating.

Passing the estimated due date does not by itself show that the baby is unwell. Your maternity team considers how the pregnancy was dated, your health, the baby's movements and growth, and whether labour has begun.

As pregnancy continues, the placenta may become less efficient and the amount of amniotic fluid may fall. These possibilities are why clinicians discuss monitoring and a plan for birth instead of relying on the calendar alone.

Keep every scheduled maternity appointment and pay attention to your baby's usual pattern of movement. Your clinician may review the dating scan, check your blood pressure and discuss fetal monitoring, ultrasound assessment, a membrane sweep or induction of labour.

Do not try herbal products, supplements or physical methods intended to start labour without checking with your maternity team. Some can cause unwanted contractions, interact with medicines or be unsuitable for your pregnancy.

Contact your maternity unit promptly if your baby moves less than usual or the movement pattern changes. Do not wait until the next day to report reduced movement.

Seek urgent assessment for vaginal bleeding, leaking fluid, severe or persistent abdominal pain, a severe headache, vision changes, sudden swelling, fever, or regular painful contractions. If you feel seriously unwell or cannot reach your maternity unit, use emergency services.

Ask how confident the team is in your due date, what monitoring is planned, which changes should prompt a call, and when they would recommend helping labour to start. You can also ask what a membrane sweep or induction involves and how your preferences will be included in the birth plan.