How does my doctor or nurse figure out my due date? — To figure out your due date, your doctor counts 40 weeks from the first day of your last monthly period.

If your periods are not regular, counting won’t give a correct due date. In that case, your doctor will do an ultrasound to figure out your due date. An ultrasound can create pictures of your baby when it is inside your body. Your doctor can use these pictures to measure your baby’s size and figure out your due date. The earlier in pregnancy that this is done, the more accurate it is.

According to 2014 SOGC Guidelines, the most accurate dating (and thus the new standard of care) is determined by the first ultrasound (from 7-23 weeks).

When is a baby overdue? — A baby is overdue if he or she has not been born by 42 weeks (2 weeks after the due date). A pregnancy that lasts longer than 42 weeks is also called a “postterm pregnancy” or “postdated pregnancy.” This rule is somewhat different for women over the age of 35-40 years old. Their risk of stillbirth is increased after term is reached and therefore induction is considered earlier.

What can cause a baby to be overdue? — Doctors don’t usually know. But a woman has a higher chance of having her baby after the due date if:

• It’s her first pregnancy
• She’s already had a baby that was born after its due date

Why is it a problem for babies to be born after 42 weeks? — Babies born after 42 weeks have a higher chance of having problems, such as:

• Being too big (heavier than 10 pounds) – A big baby can get hurt if it cannot easily fit through the birth canal. A big baby can also damage the mother’s body when it comes out through the birth canal. Sometimes, the mother has to have a c-section.
• Having a bowel movement in the amniotic fluid before birth – Babies who breathe in some of their amniotic fluid with bowel movement in it can have breathing problems after they are born.
• Other problems that can happen are:
• The placenta might not work as well as it did earlier in the pregnancy – The placenta is the organ that brings the baby nutrients and oxygen and carries away waste.
• There can be too little amniotic fluid (water) surrounding the baby in the uterus – If there is not enough amniotic fluid, the umbilical cord can get squeezed. If the umbilical cord is squeezed, the baby might not get enough oxygen and nutrients from the placenta.

What happens if I am still pregnant after my due date? — If you are still pregnant after your due date, your doctor will do tests to check your baby’s health. Most doctors do these tests at 41 or 42 weeks, but some women have these tests earlier. The tests can check:

• Your baby’s heartbeat
• Your baby’s breathing and movements
• The amount of amniotic fluid that surrounds your baby in the uterus

• Let your pregnancy continue until your body is ready to give birth
• Recommend that you have the baby soon

What if my doctor or nurse recommends that I have my baby soon? — If your doctor recommends that you have your baby soon, he or she will discuss your choices.

If your body isn’t ready to give birth, your doctor can give you medicines to help start your labour. When doctors use medicines to help start a woman’s labour, they call it “inducing labour.” These medicines often work.

Inducing labour — The optimal time to deliver a baby in a woman who is postterm is sometimes hard to determine. The healthcare provider and woman must consider the risks and benefits of continuing the pregnancy, the results of antenatal testing, and the condition of the cervix (the lower part of the uterus, which opens into the vagina). Normally, the cervix begins to dilate (open) and efface (thin) towards the end of a woman's pregnancy. Inducing labour is more likely to fail in women whose cervix is not dilated or thinned, which could require the woman to undergo cesarean birth.

Most healthcare providers will induce labour if it does not begin spontaneously by 41 to 42 weeks of gestation. For a woman whose cervix is not favorable, labour can be induced with a medication applied directly to the cervix or in the vagina, which causes the cervix to soften and dilate. Cervical change may also be accomplished using mechanical methods such as a Foley catheter bulb. Most women, including those whose cervix is favorable, will also require an intravenous medication (oxytocin), which stimulates the uterus to contract; uterine contractions further stimulate cervical dilation and effacement. If induction of labour does not completely dilate and efface the cervix, or if complications develop that require the baby to be delivered quickly, a cesarean delivery is usually performed.

Will my baby be healthy if he or she is born after the due date? — Most babies born after their due date are healthy. But babies born after their due date can look a little different at birth and have:

• Long and thin arms or legs
• Dry or peeling skin
• Long hair and nails

Few studies have examined long-term outcomes (eg, growth and development patterns, intelligence) of postterm infants. In general, the outcome appears similar in both postterm and term infants