What Meghan Markle — & Every Mother — Needs To Know About The Fourth Trimester

Baby Sussex, a.k.a. Archie, is 25 days old, but he might prefer to still be in the womb. That’s because he is still squarely in the so-called “fourth trimester,” or first three months of a new baby’s life (even though this particular newborn is living a v. fab life and maybe even preparing for his first trip to America soon).

The phrase “fourth trimester” was first popularized by Harvey Karp, MD, the popular pediatrician and child development expert. Karp’s reframing of the first three months of a baby’s life as a sort of final trimester of pregnancy does have a method to its madness: Karp counsels parents to think of their children as “born too soon,” as he phrases it in his book, The Happiest Baby on the Block. After all, anyone who has watched a nature documentary knows that human babies, royal or no, are born a lot less capable than giraffes or elephants are. But Karp takes it a step further, encouraging new parents to create womb-like conditions for their new child. The “fourth trimester” is also a handy way to remember what you can expect from the baby in the first months: not much. Just like in the womb, “fourth-trimester” babies mostly sleep and eat. All that cute cooing and babbling comes later.

But aside from reframing what you can expect (when you’re done expecting) from your baby, it can be useful for new moms who have given birth to think of the first three months as a “fourth trimester” for themselves, too, as their body continues to change and adjust post-birth.

It’s a vulnerable time for new moms, with many physical, anatomical and hormonal changes, as well as new, and sometimes overwhelming, emotions in relation to caring for a newborn,” Jane van Dis, MD, an OB/GYN and the medical director of Maven Clinic, tells SheKnows. Just like the actual three trimesters of pregnancy saw seismic changes in the mother’s body, the fourth trimester is a time of huge transformation, as the body adjusts to a) no longer supporting a fetus internally and b) supporting a new alive-human externally. And that’s even before you factor in the ever-changing sleep schedule of both the new baby and the new parents.

Prince Harry and Meghan Duchess of Sussex pose together with their newborn son Archie Harrison Mountbatten-Windsor in Windsor
Image: Domic Lipinski/PA/EPA-EFE/Shutterstock.

At the start of the fourth trimester, the postpartum uterus will shrink back to size, a process that can take up to four weeks. The body also releases all that extra fluid that was required for pregnancy, which may mean increased urination on Mom’s part, and even night sweats. Simultaneously, breastfeeding means more changes: breasts expand as the milk comes in, and those who breastfeed and/or pump may also experience an increase in appetite and thirst, as Amy Berg, a midwife and fourth trimester specialist, explains to SheKnows. Berg finds that framing her post-natal services as “fourth trimester support” is helpful for the new families she serves.

“Re-framing the postpartum period as an additional trimester to pregnancy bring[s] just how important and vital it is to monitor and support the postpartum period as much as the pregnancy itself,” Berg says.

That goes for everybody involved. Van Dis emphasizes that postpartum follow-ups for both mom and baby are vital. And aside from the expected changes in the body, there are a few other complications to be on the lookout for, Van Dis explains. Damage to the pelvic floor, which is common during birth, can lead to infections and permanent harm if not treated. Thyroid problems are also common in up to 10 percent of women in the U.S. postpartum, because of the hormone changes during pregnancy. Additionally, both van Dis and Berg emphasize the importance of screening for postpartum depression (PPD) and its milder cousin, “the baby blues.” (Singer Jordin Sparks recently spoke about her PPD, explicitly linking it to the fourth trimester period.) 

Baby blues, or initial feelings of sadness, affect 80% of new moms. If it lingers more than two weeks, it may be more serious postpartum depression, but here, Van Dis emphasizes that you’re not alone. One in three women experiences some form of anxiety or depression beyond the baby blues. And it’s not just because you’re sleeping less and likely overwhelmed and stressed. Hormone levels that have risen threefold (or higher!) have come crashing down overnight, which can cause depression. 

“New moms need to understand that their mental health is, at least in part, a result of an actual transformation and remodeling of the maternal brain,” she says. Reaching out for help, both to a partner and to specialists, during either baby blues or postpartum depression is vital. 

meghan markle prince harry baby archie
Image: Domic Lipinski/PA/EPA-EFE/Shutterstock.

Besides continuing to care for your own body, fourth-trimester moms can also do well to take as much pressure as possible off themselves in the first three months. Here, Karp’s original advice towards primarily worrying about cuddling comes in handy. “Sleep training before six months does not have sound evidence,” adds Berg. This may sound like bad news, but, in another context, it can be a reminder that you don’t have to set high standards for yourself or your baby. Whatever you do during the first three months also doesn’t have to represent your sleeping habits for all of parenthood, either. Common advice to new moms? Sleep when you can, knowing you can return to sleeping just at night in a few months — no need to rush.

Similarly, van Dis says she can sympathize with another common struggle of early motherhood: breastfeeding. Van Dis found breastfeeding to be far more difficult than she had expected, and her saving grace was finding a local support group. “It didn’t help my milk production, but it helped me feel less alone,” she says. It was also an important lesson about the fourth trimester: It was, van Dis says, “the realization that it’s nearly impossible to accomplish new motherhood without help.” And that help can come from family, friends, experts like lactation consultants, and more.

Amidst all these challenges, the fourth-trimester framing can also be a useful reminder that this isn’t forever — or even all of the first year. By two months, a baby may require as  little as two fewer feedings per day. Throughout the fourth trimester, babies can also begin to sleep longer, be better cared for by a partner or family member (not just mom), and also become more interactive.

The biggest gift new moms can give themselves is grace, Leah Keller, a personal trainer and founder of the Every Mother workout program, tells SheKnows. She practices what she preaches as well; despite the expectations some might have of postpartum workout programs (rigorous, regimented, all about losing that so-called “baby weight”), Keller says that listening to your own body on all fronts is most important. That includes eating when you are hungry, sleeping when you are tired (and able to sleep), and starting out slow when it comes to exercise. That can mean as little as a walk around the house, then a short walk around the block. And yes, that extends to even the newly-entitled mother to the seventh in line to the British throne.

Another bit of grace Meghan Markle deserves as much as every mother in the fourth trimester? The ability to do what is best for her as well as her new family, Britsh tabloids be damned.

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