Postdates Pregnancy

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What is a postdates pregnancy?

In general, a postdates pregnancy is when your pregnancy goes past your due date. A pregnancy is considered to be term between 37+0 and 42+0 weeks. The average length of pregnancy is 40 weeks (280 days). However, it is normal for pregnancies to go past 40 weeks. Only 5% of babies are born on their due date (AOM 2022). A postdates pregnancy is any pregnancy that goes past 40 weeks and 0 days (due date). A post-term pregnancy is any pregnancy that goes past 42 weeks and 0 days.

According to the Association of Ontario Midwives (AOM), in 2018, approximately half of midwifery clients in Ontario gave birth to their babies after 40+0 weeks (AOM, 2022). Some factors make it more likely a pregnancy will extend past 40 weeks, including:

  • A family history of postdate pregnancies
  • First pregnancy
  • A higher BMI
  • Maternal age over 30
  • Baby is male

Why does having a postdates pregnancy matter?

The majority of babies are healthy regardless of when they are born. However, some risk factors increase when a pregnancy extends past 41+0 weeks. Some of these risk factors include:

  • Meconium Aspiration Syndrome
  • Macrosomia
  • Stillbirth
  • Cesarean Section

What happens if the baby is not born by her/his due date?

Your midwife may recommend some natural labour stimulation methods, including:

  • Preparing yourself emotionally and physically
  • Belly Massage
  • Intercourse
  • Acupuncture/Acupressure
  • Evening primrose Oil
  • Homeopathics
  • Stretch and Sweep
  • Red Raspberry Leaf Tea
  • Relaxation
  • Exercise
  • Caster Oil

Ask your midwife for more specifics on these methods.

At 41+0 weeks your midwife will recommend increased monitoring for your baby’s well-being. Some methods of increased monitoring include:

  • Fetal movement kick counts
  • Non- stress tests (NST)
  • Ultrasound for a biophysical profile (BPP) and growth

If your pregnancy goes beyond 40 weeks your midwife will discuss your options with you with regard to labour. Three primary options exist:

  • Expectant management: Waiting and letting your body start labour on its own. Your midwife will advise you of a plan to monitor your baby’s well-being during this expectant management timeframe. If any concerns or issues arise, your midwife may recommend induction.
  • Non-Medical methods: As listed above these labour stimulation methods can continue to be used. It is important to remember that these methods do not guarantee labour will start. The primary non-medical method midwives can offer is a stretch and sweep. A stretch and sweep is an internal exam, where the midwife uses two fingers to assess the cervix. Depending on the dilation (opening) of the cervix, the midwife may be able to widen the opening of the cervix (stretch) and pass their finger between the inside of your cervix and the bag of waters (sweep). This process can be uncomfortable, but lasts less than 2 minutes and may help to stimulate labour. Your midwife may offer multiple stretch and sweeps.
  • Induction of Labour: As per local guidelines, induction of labour can be offered to low-risk postdate clients after 41+0 weeks, with the majority of inductions occurring at 41+3 weeks. Please see Induction of Labour for more information.

Will postdates pregnancy affect birthplace choice?

Postdates pregnancy will not necessarily impact birthplace choice. However, as previously discussed, having a postdates pregnancy can increase some risk factors which may impact your choice of birthplace. All inductions of labour occur in the hospital. Ask your midwife to discuss options specific to your care, risk factors and pregnancy. Feel free to review the additional resources below for more information.