When Does The Placenta Stop Working During Pregnancy?

When Does The Placenta Stop Working During Pregnancy?

Are you 40 weeks and wondering when does the placenta stop working during pregnancy?

Many women are told their placenta stops working after 40 weeks of pregnancy.

Sounds pretty scary.

The mere mention of any threat to her baby is usually enough for any woman to agree to an induction.

When Does The Placenta Stop Working During Pregnancy?

The placenta can, in fact, stop working.

But it doesn’t necessarily stop working after 40 weeks.

It can happen during any stage of pregnancy.

It’s important to know what this means and how it can affect your birth care.

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How Does The Placenta Work In Pregnancy?

The placenta is an organ that grows in the uterus during pregnancy.

In almost all pregnancies, the placenta provides everything a growing baby needs until birth.

It provides oxygen and nutrients to your growing baby via the umbilical cord.

It also filters toxins and transfers waste from your baby’s body to yours, so your body can get rid of them.

The placenta begins to form about a week after conception.

It doesn’t fully develop, however, until the end of the first trimester.

Does The Placenta Stop Working During Pregnancy?

Prevailing wisdom insists after a certain time in pregnancy the placenta stop working after a certain time in pregnancy.

This is usually 40 weeks or after your estimated due date.

However, this idea the placenta automatically stops working after 40 weeks is a myth.

It’s not based on any evidence whatsoever.

So how did this idea come about?

In 1954, Dr Stewart Clifford described a disorder in newborn babies who were born after their due dates.

The features of the disorder were:

  • Dry peeling skin
  • Overgrown nails
  • Abundant hair
  • Visible creases on palms and soles
  • Minimal fat deposits
  • Skin colour tinted green-yellow, due to meconium staining
  • Decreased altertness
  • Increased respiratory distress.

Dr Clifford called it post-maturity syndrome, and speculated the cause of this syndrome was placental insufficiency.

What Is Placental Insufficiency?

Very rarely, the placenta doesn’t function properly. This can happen if it’s damaged or doesn’t form normally.

The medical term for this is placental insufficiency – also called uteroplacental insufficiency or placental dysfunction.

Placental insufficiency affects how the placenta delivers blood, nutrients and oxygen to the fetus.

Post-maturity syndrome and placental insufficiency do occur.

But there’s no evidence to show pregnancy length directly affects the condition of the placenta.

Despite this, care providers promote the idea the placenta deteriorates at the end of pregnancy, when a woman is ‘full term’.

But there is a wide range of interpretations of what ‘full term’ means.

Each individual woman has her own gestation point for full term. This point is unknown until she goes into labour.

What Causes The Placenta To Stop Working Properly?

The condition of the placenta (and the baby) depends on the individual health of the mother and the baby.

Placental function is affected by:

  • Smoking
  • Drinking alcohol
  • Taking drugs, particularly cocaine, heroin and methamphetamine
  • Diabetes
  • High blood pressure
  • Preeclampsia
  • Diabetes
  • Blood clotting disorders

Other factors that can lead to placental insufficiency:

  • The placenta doesn’t attach properly to the uterine wall
  • Your placenta separates early (placental abruption)
  • The placenta is too close to, or is covering, the cervix (placenta previa)

What Are The Symptoms When The Placenta Stops Working During Pregnancy?

There aren’t any obvious symptoms in the mother, so if you have placental insufficiency it’s very likely you won’t know.

Of course, there are some clues you can watch out for.

These things can lead to early diagnosis of placental insufficiency:

  • Your belly isn’t growing much or at all (compared with previous pregnancies)
  • Your baby isn’t moving much

If placental abruption or preterm labour occurs, you might notice vaginal bleeding, cramping or pain.

Normally, routine prenatal check ups will pick up placental insufficiency.

What Happens To The Baby When The Placenta Stops Working During Pregnancy?

The placenta is a lifeline for your growing baby.

Therefore, if something causes the placenta to stop working, it will be unable to support your baby fully.

This can cause:

  • Birth defects, especially if the problem occurs early in pregnancy
  • Fetal growth restriction
  • Low birth weight
  • Fetal distress
  • Premature birth
  • Increased risk of maternal complications.

Will My Placenta Stop Working During Pregnancy?

There has been no research that shows if or when placentas stop working in healthy low risk women.

Even so, this is one of the most common reasons women are induced after 40 weeks.

Inductions are often done due to fear of the placenta reaching an ‘expiry date’ and no longer working.

However, research shows induction of labour for post-term pregnancy is linked to negative outcomes. It has few benefits for mothers and babies.

This review looked at studies that included women with healthy, low risk pregnancies.

The researchers found induction at 41+0–6 weeks increased the risk of:

  • C-section (the overall rate)
  • C-section due to failure to progress
  • Chorioamnionitis
  • Labour dystocia
  • Precipitate (fast) labour
  • Rupture of the uterus.

The review also showed induction at 41+1-6 weeks decreased the risk of meconium stained fluid and oligohydramnios (low amniotic fluid).

The researchers found waiting for labour to begin until 42+0-6 weeks meant about 70% of women went into labour spontaneously.

What Happens If My Placenta Stops Working During Pregnancy?

In almost all cases, placental insufficiency is picked up during routine prenatal checks.

Test that confirm your placenta isn’t working well include:

  • Ultrasound, to measure the placenta
  • Ulrasound, to measure the fetus
  • Maternal blood test, to look for proteins made by baby’s liver (alpha-fetoprotein)
  • Non stress test.

Treatment for placental insufficiency depends on your gestation, and the reason for the insufficiency.

Your care provider will treat and get under control any conditions you have.

Diabetes or high blood pressure can cause the placenta to stop working.

If you are diagnosed with placental insufficiency later in your pregnancy, you might need extra monitoring to make sure your baby is growing and healthy.

Care providers usually suggest steroids for lung development, in case of preterm birth.

Or it might be decided your baby should be born sooner; an induction or c-section might be suggested.

It’s important to have all possible information before making these decisions.

What Did I Do To Make My Placenta Stop Working During Pregnancy?

Placentas don’t have a natural expiry date. Your placenta will not stop working just because it has reached 40 weeks of age.

In other words, if your placenta stops working, it’s due to some other factor.

If care providers suggest induction because your placenta will stop working after a certain date, ask them to explain the reason they think it will stop working.

You can prevent some causes of placental insufficiency.

Make healthy choices before you conceive, and during pregnancy. Make sure you have good prenatal care.

If you’re planning to conceive or are pregnant, you should certainly refrain from smoking, drinking alcohol and taking drugs.

Eat a healthy diet and ensure you are getting adequate nutrients to help your body prepare for a healthy pregnancy.

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Sam McCulloch enjoyed talking so much about birth she decided to become a birth educator and doula, supporting parents in making informed choices about their birth experience. In her spare time she writes novels. She is mother to three beautiful little humans.

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