The fourth trimester

The fourth trimester
We’re hearing more and more about the “fourth trimester” after pregnancy. What exactly is it and where did the concept come from?

We’re hearing more and more about the “fourth trimester” after pregnancy. What exactly is it and where did the concept come from?

What is the fourth trimester?

The fourth trimester is the 12-week period following the birth of a baby. It is a time of transition, both for the parents—especially the mother—and for the newborn, who needs a safe, warm, and intimate environment to adapt to their new life.

The origins of the fourth trimester

American author Jean Liedloff is one of the people who introduced the concept of the fourth trimester in the 1970s. After spending time among Indigenous communities in Venezuela, she came to the conclusion that for optimal development, babies need to be in conditions similar to those in which our species evolved. She found that this process follows a continuum, meaning a sequence of very specific experiences. The first months of life are therefore a continuation of pregnancy.

After they’re born, a baby still needs some of the elements that cradled them in the womb, such as physical proximity. Liedloff proposed this theory in her book, The Continuum Concept, where she advocates practices such as babywearing, co-sleeping, and breastfeeding.

This book was later a source of inspiration for noted pediatrician William Sears. In his books, Dr. Sears promotes parenting practices based on attachment theory that are very similar to those supported by Liedloff.

However, it was Dr. Harvey Karp who popularized the term fourth trimester in the 2000s. According to Dr. Karp, babies are born too early. This is why, in order to soothe them, it is necessary to imitate the environment of the uterus. Among other things, Dr. Karp recommends rocking your baby and meeting their need to suck. He also promotes swaddling, though experts recommend exercising caution with this practice.

These definitions of the fourth trimester are largely based on the baby’s experience. However, some health professionals associate the fourth trimester with the mother’s experience, as she needs to both physically recover from childbirth and adjust to her new role as a mother. Although these two perspectives can be complementary, they are rarely presented together.

That said, more and more experts now refer to the fourth trimester as a time when mother and child should be in the same bubble. For example, Ingrid Bayot, who trained as a midwife in Belgium and is now a perinatal coach in Quebec, published a book called Le quatrième trimestre de la grossesse in 2018. Her book seeks to raise awareness about the issues that affect both baby and mother in the months following birth. In particular, she emphasizes the idea that a newborn is a fetus outside of the womb, and that a mother’s body does not fully return to the way it was before, even though the characteristics of pregnancy disappear.

The fourth trimester for the baby

According to the idea that babies are born too early, a newborn can be compared to a fetus outside their mother’s womb during their first few months of life. This is why this period is referred to as a fourth trimester.

Some experts believe that pregnancy ends before the baby is ready to face the world. Because babies are born very immature from a neurological point of view, they are entirely dependent on their caregivers. This explains the strong relationship between a mother and her baby, who form an intimately bonded unit known as a dyad.

To help their baby adjust to life outside the womb, parents can use strategies that promote closeness with their newborn.

The fourth trimester for the mother

According to the mother-centred view of the fourth trimester, while the fetus becomes a baby after birth, it is also at this time that the mother must adjust to her new role. During this period, the mother adapts to her new responsibilities. From a physical point of view, she is also experiencing significant hormonal changes in addition to having to recover from childbirth, which may have been very demanding.

Here are some of our fact sheets that discuss the aftermath of childbirth and a mother’s adaptation to her new role.

The other parent and close family members can also help out.

The fourth trimester for the father

During the fourth trimester, fathers also have to adjust to their baby’s arrival. They have their own way of reacting to the birth, and they may find their identities changed by their new role as dads. For example, some fathers will become fiercely protective of their families.

Things to keep in mind

  • A baby is completely dependent on their parents for the first few months after birth.
  • The mother must recover from childbirth and adapt to her new role as a mom.
  • The father also needs to get used to the arrival of the baby.
  • Family and close friends can support the mother, father, and baby during this transition period.


Naître et grandir

Scientific review: Louise Godin, graduate nurse and IBCLC lactation consultant
Research and copywriting: The Naître et grandir Team
May 2021

Photo: GettyImages/1134293514



Note: The links to other websites are not updated regularly, and some URLs may have changed since publication. If a link is no longer valid, please use search engines to find the relevant information.

  • Bayot, Ingrid. Le quatrième trimestre de la grossesse. Toulouse, Éditions Érès, 2018.
  • Bilodeau, Mélanie. Soyez l’expert de votre bébé. Montreal, Éditions Midi trente, 2019.
  • Doré, Nicole, and Danielle Le Hénaff. From Tiny Tot to Toddler: A practical guide for parents from pregnancy to age two. Quebec City, Institut national de santé publique du Québec.
  • Gueguen, Catherine. Pour une enfance heureuse : repenser l’éducation à la lumière des dernières découvertes sur le cerveau. Paris, Éditions Robert Laffont, 2014.
  • Gueguen, Catherine. Vivre heureux avec son enfant : un nouveau regard sur l’éducation au quotidien grâce aux neurosciences affectives. Paris, Éditions Robert Laffont, 2015.
  • Karp, Harvey. “What is the fourth trimester?”
  • Lavollay, Bernadette. Les vrais besoins de votre bébé : les découvertes qui révolutionnent la naissance et les premiers mois. Paris, Éditions Les Arènes, 2018.
  • MacNamara, Deborah. Rest, Play, Grow: Making Sense of Preschoolers (Or Anyone Who Acts Like One). Vancouver, Aona Books, 2016.

    Citation du livre anglais :

  • National Childbirth Trust. “What is the fourth trimester?”
  • Odent, Michel. Le bébé est un mammifère. Paris, Éditions l’Instant Présent, 2014.
  • Pickert, Kate. “The Man Who Remade Motherhood.” TIME.
  • Stuebe, Alison M., and Kristin P. Tully. “Optimizing Maternal-Infant Health: Ameliorating the Mismatch between Evolved Dyadic Needs and the Current Culture of Health around the 4th Trimester.” In Integrating Evolutionary Biology into Medical Education: For Maternal and Child Healthcare Students, Clinicians, and Scientists, edited by Jay Schulkin and Michael Power, Oxford University Press, 2019, 288 pp.
  • The Liedloff Continuum Network

    . “Understanding The Continuum Concept.”
  • Verbiest, Sarah B., et al. “Promoting Maternal and Infant Health in the 4th Trimester.” Zero to Three, 2017.
  • Zephyr, Lory. Maman en construction : petit chantier de réflexion sur la maternité. Montreal, Les Éditions de l’Homme, 2018.