From Zygote to Baby: How to Build a Human

Here is an amazing infographic on embryogenesis from Tabletop Whale‘s Eleanor Lutz.

How to Build a Human: Human embryo and fetus development from fertilization to birth. Eleanor Lutz, 2014.

In this stunning data visualization, Lutz illustrates the process of fetal development, including what the baby looks like in each of the three trimesters, when the eyelids form (~12 weeks), when the fingers and toes separate (9 weeks), to when the taste pores develop (~16 weeks), to name a few.

Imagine how helpful this would be for students, or even in a childbirth education class? I’ll start bringing this around with me to each of my prenatal visits.

Printouts of this visualization can be found here. This post and more can be found on Lutz’s website: TabletopWhale.

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First hour of life for newborns: a timeline

Photo by Mikaela Wapman

Photo by Mikaela Wapman

Laura Sanders of Science News recently published a post on a Timeline of a Baby’s First Hour.

In the post, she stumbles upon a 2011 study from Sweden regarding observations of 28 of “the most mysterious creatures on the planet: brand-spanking-new humans.”

Sanders goes on,

Videos of babies in their first hour of life gave the researchers an unprecedented view of how newborns instinctually behave, when left to their own devices and nestled skin-to-skin on their mothers’ chests. I found the results, published in January 2011 in Acta Paediatrica, just as fascinating as the Drosophila courtship ritual.

Having supported a fair number of births in the hospital, I have witnessed many of the instincts of the newborn to cry, nurse, and sleep. Sometimes, routine tests or complications in birth interrupt the newborn’s instinctive inclinations and the maternal / infant initiation, as the hospital team performs the necessary evaluations, perfunctory tests (birth weight, length, head measurements, immunizations… the list goes on and on).

In uncomplicated, low-intervention births, new mothers are able to rest with their newborns on their chest and relish in the unique, indescribable joy of skin-to-skin. It is during these moments that the researchers from Sweden noted some key milestones in the first hour and 10 minutes of a newborn’s life, presented in median minutes:

Minute 0: Babies wail a robust, angry birth cry that helps wake up the lungs.

Minute 2: After all that wailing, babies spend less than a minute relaxing, holding perfectly still on their mothers’ chests. The authors speculate that this silent, still break might have evolved to keep babies hidden from predators.

Minute 2.5: As they start to wake up, newborns open their eyes for the first time. Babies gradually start moving their heads and mouths.

Minute 8: Babies become even more active, keeping their eyes open for five minutes or longer at a time. During this active phase, newborns seem to grow interested in eating, looking at their mothers’ faces and breasts, making sweet little “hungry” noises and moving their hands toward their mouths.

Minute 18: That was exhausting. Time for another rest.

Minute 36: Recharged newborns really kick it into high gear and begin scooting toward their mothers’ breasts, relying heavily on a sense of smell to navigate.

Minute 62: Babies nurse, most likely getting small amounts of colostrum, a pre-milk substance packed with protein and immune molecules. This early suckling stimulates the breasts to make milk and also helps mom’s uterus contract back to its pre-pregnancy size.

Minute 70: Babies fall asleep for a well-deserved break.

There you have it: the first seventy minutes of a newborn’s life, as described by science. Of course, these minute markers are median numbers drawn from a small number of newborns (n=28), and even the time tables of the babies included in the study varied substantially. Any single baby’s behavior might fall well outside of these time points.

These quantitative observations are helpful with respect to the introduction and recent emphasis that most hospitals are placing on “baby friendly” practices, designed to encourage breastfeeding and also happen to support the bond between mom and baby.

Photo by Mikaela Wapman

Photo by Mikaela Wapman

“Baby friendly” practices, as outlined by Baby-Friendly USA, state that “health care systems should ensure that maternity care practices provide education and counseling on breastfeeding. Hospitals should become more “baby-friendly,” by taking steps like those recommended by the UNICEF/WHO’s Baby-Friendly Hospital Initiative.” Initiatives to improve breastfeeding rates include forgoing formula and pacifiers, allow the mom and baby to stay together (rather than baby in nursery), and provide hospital staff to instruct and support new moms with breastfeeding.

Sanders refers to another observational study:

In the first hour of birth, babies whose chins touched the underside of their mothers’ breasts were more likely to successfully suckle than babies who didn’t do a chin-brush. These sorts of studies, which rely on carefully watching a newborn, are beginning to paint a more complete picture of what newborns might need in the moments after birth. And that understanding might ultimately be useful to the adults who want to ease the introduction of this new little person to the world.

Observations from these studies regarding the instinctive newborn behaviors – without interference from anyone – might help healthcare providers come up with better ways to encourage breastfeeding, and cut down on some of the routine tests that might be best delayed until the third (or fourth, fifth, or sixth) hour of the baby’s life.

You can read the whole article here. Via Science News.


Questions? Feedback?

Please feel free to comment, or contact me at mikaelawapman@gmail.com, or by filling out the form below:

Birth Videos

So many of us are filled with imagery of births as medical emergencies or otherwise painful, screaming, or distressing visions. These videos of various hospital and home births offer a new perspective and help us imagine that there are many, many possibilities for what birth “looks like”.

French Woman Giving Birth With Joy

A couple of things about this powerful birth:

  1. Notice her perineum. That stretch! The body is made to do this. It will stretch out, and stretch back. We’ve talked about Perineal Massage on the site, but here’s a visual aid for how a vaginal birth without lots of interventions can reduce perineal trauma and pelvic floor damage. For more information, see here.
  2. Consider how little movement and action there is in this film. The mom is free to take on any position that is comfortable to her, and she is calm. The birthing assistants (the doctor or partner, and the second doctor / midwife / nurse) are supporting her, but otherwise not doing much at all. After mom has delivered the shoulders, the male birth partner places the baby on mom’s chest. But there’s no pulling the head, suctioning, episiotomy… mom delivers baby without much assistance!

Natural Unassisted Homebirth

Birth of Sloane

A gentle film of a home birth from Natasha Hance.

Welcoming Theodore

A gorgeous depiction of sibling support during birth. “Waiting, birthing and welcoming Theodore into his new family of five. A homebirth in Tennessee. 9lbs 9oz” via Documentingdelight.org

Arden’s Labor

The calm birth of Arden, or “Sugarbaby” as some of the commenters have asserted, is via the TheLeakyBoob.

Happy watching!!


Please feel free to contact me at mikaelawapman@gmail.com, or in the form below:

“Morning Sickness” vs. Hyperemesis Gravidarum

Photo by Mikaela Wapman

Photo by Mikaela Wapman

Pregnancy-related Nausea or “Morning Sickness”

Pregnancy-related nausea is a common enough concept for most of us: nausea and vomiting during the first trimester, food aversions, and beyond.

Morning sickness – a misnomer, as it’s symptoms strike throughout the day for most women –  usually begins around the 6th week of pregnancy and tends to last for the duration of the first trimester (or until around the 14th week), but many women don’t experience relief from the symptoms for another month or so. And some women don’t feel a lessening of symptoms until they give birth, or somewhere around 40 weeks.

Pregnancy-related nausea affects over 70% of all pregnant womenAccording to Baby Center, more than half of pregnant women experience both nausea and vomiting, a quarter experience only nausea, and the remaining quarter are don’t experience any form of “morning sickness”.

Hyperemesis Gravidarum

Hyperemesis Gravidarum (HG) is a severe form of nausea and vomiting during pregnancy that is characterized by “unrelenting, excessive pregnancy-related nausea and/or vomiting that prevents adequate intake of food and fluids”. If HG is severe enough, or untreated, it can be associated with:

  • loss of greater than 5% of pre-pregnancy body weight (usually over 10%)
  • dehydration and production of ketones
  • nutritional deficiencies
  • metabolic imbalances
  • difficulty with daily activities

While the majority of women experience some form of morning sickness, around 1-3% of women are hospitalized for HG. That may seem pretty low, but these statistics offer very limited information, as many of the women who suffer from HG are treated as outpatients with mild to severe symptoms. Helpher.org – a website devoted to raising awareness about HG – goes on to say,

There are reports from hundreds, if not thousands, of women who terminated out of desperation when given the diagnosis of morning sickness and given inadequate treatment. One study by Zhang, et al of 1867 women found a 10.8% incidence of severe vomiting. Many women are not represented in current statistics which only report the number of women hospitalized as inpatients. HG is not a rare disorder.

Like more moderate forms of pregnancy-related nausea and vomiting, symptoms from HG can resolve around 21 weeks, though – for less than half of these women – can last for the duration of the pregnancy. The effects of all forms of HG are severe: considering the cost of additional doctor’s visits, outpatient care, consultations, and treatments for consultations, the annual cost could reach to one billion dollars.

Beyond the financial effects of HG are the emotional and psychological impacts: family relationships are disrupted, women could be “misdiagnosed by a disease erroneously presumed to be psychological”, and women could lose their jobs because of the debility. 

While there is no known prevention of HG, there are many ways to alleviate and manage the symptoms. These include: bed rest, acupressure, herbs (ginger or peppermint), IV fluids to restore lost hydration, electrolytes, vitamins and nutrients, tube feeding, and medications.

Distinguishing between Pregnancy-Related Nausea and HG:

Pregnancy-related nausea is what is commonly referred to as morning sickness. Symptoms of those suffering from Hyperemesis Gravidarum are generally more severe, as is depicted in the chart below (source: www.helpher.orgAmerican Pregnancy).

Why do we have pregnancy-related nausea, anyways?

Theories regarding the etiology of pregnancy-related nausea and HG are inconclusive. This is partially because pregnancy-related nausea and HG are influenced by a number of factors, and may vary among women depending on their biological makeup (genetics), body chemistry, and general health.

Theories regarding the cause of  pregnancy-related nausea and HG center on hormonal changes (increase in estrogen during pregnancy) and physical changes (relaxed esophageal sphincter) during pregnancy, since the time period is restricted to pregnancy.

Other half-witted theories include: one’s psychological state may be related to the development of pregnancy-related nausea and HG. In this vein, women who are frustrated, depressed, isolated, and / or have feelings of helplessness are more likely to experience pregnancy-related nausea or HG. Understandably, others respond by pointing to the fact that most, if not all women experience psychological effects (frustration, anger, depression, isolation, and feelings of helplessness) secondarily to  pregnancy-related nausea and HG.

At present moment, there are no conclusive theories as to the etiology of pregnancy-related nausea and HG. Click here to learn more about the many theories of pregnancy-related nausea and HG’s etiology.

Narratives from HG

To get a sense of what Hyperemesis Gravidarum (HG) can look like, check out Huffington Post ‘s post What It Really Feels Like to Have Hyperemesis Gravidarum”. An account of a third time mom who experienced HG so severe that she was hospitalized for 11 days, and spent the remaining duration of her pregnancy receiving IV fluids and medications for HG through a PICC line and stomach pump. Alexa continues,

One of the worst things about HG is how isolating it is. I cannot go out, cannot even talk on the phone for a long time because it makes me feel sick. I cannot cook, everything smells terrible to me, and even walking to the bathroom makes me vomit most days. I also have ptyalism, which is hyper-salivation, and swallowing it makes me vomit too, so I am constantly spitting into a cup. I feel disgusting.

Her account ends happily, with her giving birth to a 9 pound, 11 oz son (described by her OB as “the world’s most effective parasite”). For her, her HG improved after about 22 weeks of pregnancy, though she is the first to remind us that “far too many sufferers are severely ill until they give birth”. Read the whole thing here

For more information on Hyperemesis Gravidarum, visit www.helpher.org and beyondmorningsickness.com.

Why the Long, Difficult Birth for Humans?

Labor for first time moms averages somewhere between 10 – 20 hours. Among other Great Apes, such as Chimpanzees, labor takes on average two hours. In addition to the time in labor, human labor is described as extremely difficult compared to other primates.

What characteristics contribute to such disparate childbirths in humans and other primates?

1. The Obstetric Dilemma

The most significant tradeoffs in human evolution are evidenced at the time of birth: efficient bipedal locomotion promotes a relatively narrow pelvis, while delivering relatively large-brained babies selects for a broad pelvis. In other words, the narrow pelvic opening that is good for efficient upright walking is not so good for the delivery of large-brained humans.

The interaction of these features in our evolutionary history has shaped a female pelvis that reflects a compromise in these selective pressures: the constraints on the human pelvis due to walking on two legs, combined with the exceptionally large brains of human babies make human birth especially long and painful.

2. Bipedalism Promotes a Narrow Pelvis

Humans are the only living mammal to walk on two legs, and bipedalism requires narrow, short, squat, and basin shaped pelvic anatomies. In contrast, quadrupedal animals (like our closest relatives, chimpanzees) have pelvises that are long and two dimensional in appearance. Compare image A (the pelvis of a chimpanzee) to image C (the pelvis of a human female).

Comparison of pelves from (A) Pan, (B) Australopithecus, (C) Human female, and (D) Human male (from Lovejoy, 2005, figure 5).

Comparison of pelves from (A) Pan, (B) Australopithecus, (C) Human female, and (D) Human male (from Lovejoy, 2005, figure 5).

Notice how long the chimpanzee (image A) pelvis is compared to the squat pelvis of a human female (image C)? That humans walk on two legs is one explanation for the pronounced differences between humans and chimpanzees.

3. Big Brains and Birth

One important characteristic of primates as a group is a high encephalization quotient, or a large head and brain relative to body size. For most primates, this means that neonates at birth have heads that are close to the size of the maternal birth canal through which they must pass, making birth far from easy.

From Rosenberg and Trevathan (2002); based on Shultz (1949).

From Rosenberg and Trevathan (2002); based on Shultz (1949).

The image above describes the relationship of the maternal pelvic inlet (outer white ovals) and size of the baby’s head (dark solid ovals).

Think of a hard boiled egg. For gorillas and chimpanzees, the baby’s head is the size of the yolk, while the mother’s pelvic opening is the size of the egg white. Though baby must pass through the muscles and tissue of the birth canal, there is no bony resistance from the mother’s pelvis. For humans, imagine the hard boiled egg as the shape of the pelvic opening, and a golf ball as the baby’s head.

4. Passage through the Birth Canal

It’s not just the tight squeeze that makes birth difficult – the human birth canal isn’t a constant shape in cross-section. Thanks to bipedalism, the the birth canal is twisted in the middle, while the birth canal is described as a “relatively straight tube” for quadrupedal primates. A monkey baby has a tight squeeze through his mother’s pelvis, however her birth is significantly less difficult than a human baby’s. This is because, unlike the complicated cross-sectional area of the human birth canal, a monkey’s birth canal maintains the same cross-sectional dimensions from front to back.

Image by Karen R. Rosenberg and Wenda R. Trevathan

Image by Karen R. Rosenberg and Wenda R. Trevathan

As a human baby makes her way down the birth canal, she enters the birth canal at it’s widest side-to-side, relative to the mother’s body. But midway through, the orientation of the birth canal shifts 90 degrees, and the baby must now navigate a series of twists and turns so that her largest dimensions – the head and shoulders – are aligned with the largest areas of the birth canal.

The baby must rotate through the changing dimensions of the birth canal twice in order to navigate and pass through the differing pelvic dimensions through the birth canal’s entrance and exit. Our unique mechanism of birth is one of the distinguishing features of human birth, and adds an additional source of difficulty for so many mothers and babies.

5. Differing Degrees of Cervical Dilation

Among primates, human babies have exceptionally big brains. Because of this, the female cervix must dilate three times as much as other primates in order to deliver the big-brained, broad shouldered baby.

Image via Dr. Cheryl Knott

Image from Dr. Cheryl Knott via

Chimpanzee mothers must dilate around 3.3 centimeters before they’re able to give birth. Human mothers must dilate 10 centimeters before they’re able to deliver. The extra 6.6 centimeters of dilation takes significantly more time, but later stages of dilation are also experienced as significantly more painful. As described in the Mayo Clinic, the early stages of labor (0 – approximately 4cmaren’t always experienced as particularly uncomfortable, and certainly don’t require the same degree of attention as later stages of labor. Later stages of dilation (around 8, 9, 10 centimeters) leading up to transition and delivery are when women experience the most pain.

In Sum: the Obstetric Dilemma

Researchers eloquently describe the interaction of demands as a “tug of war” exerted on the maternal pelvis, which makes human birth significantly more risky than birth in other primates and mammals. Others have described this tradeoff as a scar of human evolutionary history, or the obstetric dilemma.

The Good News: Delivering with Company

Unlike most primates who seek solitude during parturition, virtually all women cross-culturally seek out assistance during birth from relatives, doulas, obstetricians, midwives, and other supports. While there are stories of women who had successful solitary births, studies of childbirth across cultures find that these stories are exceptional. Across cultures, women seek out both physical and emotional assistance in labor and delivery.

If you’re pregnant, consider giving birth with continuous emotional support: from a partner, family member, friend, or doula. A woman’s desire to be surrounded by familiar “others” has deep roots in our human lineage, is associated with fewer birthing complications.


Please feel free to contact me at mikaelawapman@gmail.com, or in the form below:

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References:

Aiello, L., & Dean, C. (1990). An introduction to human evolutionary anatomy. London: Academic Press.

Aiello, L., Wheeler, P., (1995). The expensive-tissue hypothesis: the brain and the digestive system in human and primate evolution. Current. Anthropology. 36, 199–221.

DeSilva, J.M., Lesnik, J.J. (2008) Brain size at birth throughout human evolution: A new method for estimating neonatal brain size in hominins. Journal of Human Evolution 55:1064–1074.

DeSilva, J. M. (2011). A shift toward birthing relatively large infants early in human evolution. Proceedings of the National Academy of Sciences of the United States of America108(3), 1022-7.

Ellison, Peter T. On Fertile Ground. Cambridge, MA: Harvard University Press, 2001. Print.

Hrdy, S.B. (2009). Mothers and Others. Harvard University Press: Cambridge Press.

Hrdy, S. B. (2005). Comes the child before man: how cooperative breeding and prolonged postweaning dependence shaped human potential. in Hunter-Gatherer Childhoods: Evolutionary, Developmental & Cultural Perspectives. Edited by: B. S. Hewlett and M. E. Lamb. Aldine Transaction: New Brunswick, 65-91.

Hodnett  ED,  Gates  S,  Hofmeyr  GJ,  Sakala  C,  Weston  J  .  “Continuous support for women during childbirth.”  Cochrane Database Syst Rev. 2011 Feb 16; (2):CD003766.

Hogan MC, Foreman KJ, Naghavi M, Ahn SY, Wang M, Makela SM, Lopez AD, Lozano R, Murray CJ. 2010. Maternal mortal- ity for 181 countries, 1980-2008: a systematic analysis of pro- gress towards Millennium Development Goal 5. Lancet 375:1609–1623.

Howell N. Demography of the Dobe !Kung. New York: Academic Press, 1979.

Kramer, K. L. a. E., P.T. (2010). Pooled energy budgets: resituating human energy allocation trade-offs. Evolutionary Anthropology. 19: p. 136-147.

Krogman WM. 1951. The scars of human evolution. Scientific American 184:54–57.

Langergraber, K.E., Schubert, G., Rowney, C., Wrangham, R., Zommers, Z., and Vigilant, L. (2011). Genetic differentiation and the evolution of cooperation in chimpanzees and humans. Proceedings of the Royal Society of London – Series B, Biological Sciences, 278: 2546-2552.

Rosenberg, K. & Trevathan, W. (2002). Birth, obstetrics and human evolution. BJOG: an International Journal of Obstetrics and Gynaecology, 109, 1199-1206.

Rosenberg KR (1992) The evolution of modern human childbirth. Yearbook Physical Anthropology 35:89–124.

Rosenman BA, Lovejoy CO, Spurlock LB, Tague RG. A reconstruction of the Sts 14 pelvis, and the obstetrics of Australopithecus [abstract]. American Journal of Physical Anthropology 1999; (Supplement 28):235.

Schultz A. The Life of Primates. London: Weidenfeld and Nicolson, 
1969.

Stoller M. The obstetric pelvis and mechanism of labor in nonhuman primates [PhD dissertation]. University of Chicago, 1995.

Tague RG, Lovejoy CO (1986) The obstetric pelvis of A.L. 288-1 (Lucy). Journal of Human Evolution 15: 237–255.

Trevathan, W. (2010). Ancient bodies, modern lives: How evolution has shaped women’s health. New York: Oxford University Press.

Trevathan, W., & Rosenberg, K. R. (2000). The shoulders follow the head: postcranial constraints on human childbirth. Journal of Human Evolution39, 583–586.

Trevathan W. Fetal emergence patterns in evolutionary perspective. American Anthropology 1988;90:674–681.

Oxorn, H. (1986). Oxorn-Foote Human Labor and Birth, 5th edition. Norwalk, CT: Appleton-Century-Crofts.

Wells, J. C., DeSilva, J. M., & Stock, J. T. (2012). The Obstetric Dilemma: An Ancient Game of Russian Roulette, or a Variable Dilemma Sensitive to Ecology? Yearbook of Physical Anthropology55, 40-71.

World Health Organization. 2006. Neonatal and perinatal mortality: country, regional and global estimates. Geneva: World Health Organization.

First Time Moms: Consider Perineal Massage

Tearing during childbirth is common (more than 70% of women experience perineal trauma in childbirth) especially for first time vaginal births, and in vacuum or forceps assisted deliveries (Beckman and Stock, 2014Aashiem, Nilsen et al. 2011). Studies have found that perineal massage before birth has a positive effect on the incidence of perineal trauma at birth among first time moms. Second time moms experience a significant reduction in pain three months postpartum.

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Pregnant [39 weeks]” by Kevin Dean is licensed under CC BY 2.0

What is perineal massage? 

Perineal massage stretches the inner tissue of the lower vagina. Perineal massage teaches you to respond to pressure in your vagina by relaxing your pelvic floor, and can increase muscle and tissue elasticity. It is also thought to enhance the hormonal changes that soften the connective tissue in late pregnancy. I include instructions on how to massage your perineum later in this post.

How do I go about it?

Typically, women start massaging around 34-35 weeks of pregnancy, and are encouraged to spend 5 – 10 minutes 1-2 times a week. Recent studies indicate that the more frequently women use perineal massage, the less likely they are to experience the benefits. Specifically, women who did perineal massage 1.5 times a week experienced a 17% reduction in perineal trauma and a 17% reduction in episiotomy. In contrast, women who massaged between 1.5-3.4 times a week experienced only an 8% reduced risk of perineal trauma. So, the less frequent the massage, the more beneficial the outcomes. 

The research:

In a Cochrane Review, women who massaged their perineum once or twice a week beginning at thirty-five weeks of pregnancy were compared to women who did nothing. Researchers found that women who were assigned to do perineal massage experienced a 10% decrease in risk of tears requiring stitches (aka perineal trauma), and a 16% decrease in the risk of episiotomy, however these findings were only significant for first time moms.

Although second time mothers did not experience the same reduction in risk of stitches and episiotomy in childbirth, second time mothers reported a significant reduction (32%) in the incidence of pain at three months postpartum. More frequent massage in second time moms was associated with a reduction in perineal pain postpartum.

So, for first time moms only, perineal massage 1.5 times a week during pregnancy has been found to decrease the risk of episiotomy, as well as a decrease the risk of trauma requiring stitches. 

For second time moms, frequent perineal massage (between 1.5-3.4 times a week) is associated with a reduction in pain postpartum.

How to do a perineal massage:

  • Find a comfortable position (legs bent outward while lying on the bed, standing with one foot on the edge of a bathtub or counter, sitting on the toilet)
  • Use unscented oil such as olive, sunflower, or sweet almond oil. Insert one or both thumbs in the entrance of the vagina.
  • Pressing towards the back of your vaginal wall, move your thumbs back and forth in a U-shape, focusing on relaxing your muscles at the same time. First downward for 2 minutes, and then sideways for 2 minutes.
  • Massage for around 5 minutes each time. Remember your breath as you do this – count to four on your inhales, hold, and count to four on your exhale.
  • You can try pushing harder each time you do a perineal massage.

Or if you prefer, a medical explanation how-to: “Digitally stretch perineal tissues by inserting lubricated fingers 1.5 inches into the lower portion of the vagina and slowly massaging downward in a U-shaped movement” (Beckmann and Stock, 2014).

Questions? Feel free to check out any of these sources: 

The length of human pregnancies can naturally vary up to 5 weeks

Science Daily covers a recently published study from journal Human Reproduction, investigating the variability in the length of human pregnancy:

Normally, women are given a date for the likely delivery of their baby that is calculated as 280 days after the onset of their last menstrual period. Yet only four percent of women deliver at 280 days and only 70% deliver within 10 days of their estimated due date, even when the date is calculated with the help of ultrasound.

Already 40 weeks pregnant? Not to worry, that’s within the range of normal! Researchers found that the average length of pregnancy was 328 days, which is 38 weeks and two days, though the length of pregnancies can vary by as much as 37 days.

“We know that length of gestation varies among women, but some part of that variation has always been attributed to errors in the assignment of gestational age. Our measure of length of gestation does not include these sources of error, and yet there is still five weeks of variability. It’s fascinating.”

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Pregnancy” by Robert Pecino Martinez is licensed under CC BY 2.0

In addition to variation in gestation length:

Embryos that took longer to implant also took longer from implantation to delivery, and that pregnancies that showed a late progesterone rise were significantly shorter by an average of 12 days than pregnancies with an early rise.

Dr Jukic said: “I am intrigued by the observation that events that occur very early in pregnancy, weeks before a woman even knows she is pregnant, are related to the timing of birth, which occurs months later. I think this suggests that events in early pregnancy may provide a novel pathway for investigating birth outcomes.”

Read the whole story here.

Gestation and the Maya calendar

Mayan_Zodiac_Circle

Maya life revolves around the concept of time. So much so that children are named after the date of which they’re born, and agricultural, civil, religious decisions were derived based on a priest’s reading of sacred calendars. The Maya civilization had a distinctive, complex, and precise calendar system which consisted of more than 20 intercalated counts, or cycles, of differing lengths.

The Tzolk’in, or Sacred Round is a 260 day calendar made up of 20 days of 13 numerical coefficients, and is the central hub of Maya time. The Tzolk’in lists sacred days, omens, sacrificial, warring and agricultural advice. The Haab’ is a 365 day calendar of the solar year. The Haab’, functioning very similar to our own calendar, is made up of 18 named “months” of 20 days each, with a much-dreaded interval of 5 unlucky days tacked onto the end of the Haab’ cycle. The Haab’ combines with the Tzolk’in to create 18,980 different permutations of days, forming the complex 52-year Calendar Round. To calculate periods of time longer than the 52 year cycle of the Calendar Round, the Maya used the Long Count calendar.

From this introduction of Maya time, we can look more closely at one interesting aspect of the Tzolk’in cycleThe key constant of the Maya calendar system is the Tzolk’in 260-day cycle, made up of 20 day names and 13 numerical coefficients.

tzolkin

Representation of the Tzolk’in calendar. The 13 numbers (depicted as the inside circle) combine with each of the 20 day signs (the larger circle), representing the 260 day Tzolk’in cycle.

But what is the significance of 260 days?

The Tzolk’in cycle results in different permutations of the 20 day-signs with a number from 1 to 13. 20 is an important number for Mayan mathematics. Namely, 10 fingers + 10 toes = 20. One-word translations of the 20 day signs are as follows: earth, wind, house, lizard, serpent, death, deer, rabbit, rain, dog, monkey, tooth, staff, jaguar, eagle, owl, quake, knife, storm, and birth. These one-word translations are only sketches of the different meanings of the day-signs, but nonetheless point to an important theme. The 20-day sequence of day signs ends with birth, and illustrates how the Maya concept of time is not only cyclical, but also leads to the development of something new. That the sequence ends with birth lends itself to understanding Maya time as the spiral growth of human and cosmic proportions, beyond the scope of the cycle of a clock.

The Maya conceive of 13 phases of the moon from new to full, which may explain the importance of the number 13 in the Tzolk’in calendric cycle. During a new moon, the moon isn’t visible to the observer until around the second day. Counting forward, the time from new to full moon, or the growth cycle of the moon, takes approximately 13 days. By day 13, the moon appears full for 2 – 3 days. In this way, the number 13 symbolizes the growth of the moon from new to full. While there are alternative interpretations of the number 13, the significance of the number 20 and 13 addressed above introduce one consistency in the Maya worldview: the microcosm (individual)  and macrocosm (universe) mirror each other.

It is possible that the 260-day Tzolk’in cycle originated to predict when a woman would give birth. The length of human gestation is approximately 260 days, from the number of days between first missed period and birth. Therefore, a child conceived on 1 Imix would be born on 1 Imix of the following Tzolk’in year. Interestingly, these those 260 days corresponds to nine lunar cycles of 29.53 days each. That the 20 day signs begin with earth and end in birth support this theory.

The importance of the number 13 has reference to the lunar growth cycle, and the 260-day Tzolk’in calendar is made up of nine lunar cycles of 29.53 days each. The combination of these features is one reason for calling the Tzolk’in calendar a “lunar” calendar. While this explanation of the origin of the Tzolk’in calendar can never be proven, it nonetheless introduces the importance of astronomy for the Maya. Maya goddess, Ix Chel (pronounced Ish-Chel) supports the synthesis of individual with the cosmos, or birth with moon. Ix Chel is considered a woman’s god, and represents birth and medicine. She is also associated with the moon, and has been called “Our Mother Moon“.

Ixchel_Dresden_Codex

Representation of Ix Chel, Maya goddess of childbirth, motherhood, and the moon. Source: Dresden Codex

This brings up another complex idea: the triangular relationship between the earth, moon, and sun. These features further point to the macrocosmic relationship of the earth, moon, and sun in the understanding of the Tzolk’in calendric cycle.

It’s also possible that the 260 day cycle tracked a different sort of fertility: the period from planting to harvest. 260 days corresponds to the time between planting and harvesting certain types of maize, from zenith to zenith. According to creation myths such as the Popol Vuh, as well as Preclassic artistic representations, humankind was fashioned out of maize by the gods. As an agricultural society, maize is the staff of life and survival depends on the production and harvest of maize. In this sense, the life cycle of maize is emblematic of the human lifecycle.

That the Maya combine the Haab’ and the Tzolk’in rounds introduces an important aspect of the Maya worldview. The Haab’ is the calendar of the yearly cycle of the sun, while the sacred Tzolk’in count symbolizes one’s inner dimensions of reality. Combining these two aspects of human experience – the inner with the outer, microcosmic with the macrocosmic – synthesizes the two into one inclusive cosmo-conception. The significance of the numbers 13 and 20, which make up the Tzolk’in count further support the Maya worldview that the inner and outer realms mirror each other. Furthermore, Ix Chel, goddess of childbirth, motherhood, and the moon fully acknowledges the interaction of the individual processes (in this case, birth) with the cosmos (specifically, the moon). Agricultural and gestation explanations for the 260 day Tzolk’in cycle both illustrate how Maya notions of time are tethered to microcosmic and macrocosmic forces. Though the origin of the Tzolk’in 260 day count is unknown, the Tzolk’in has multiple interpretations, and the overlap of these two explanations may explain why 260 days is sacred.

Maya conceptions of time involve an approach of mutual involvement, connection, and overlapping inclusion, rather than a dualistic approach seen in other systems of time. The cycles of growth in the individual mirror those developments in the cosmos, creating a worldview of complete acknowledgement of spirit in matter, and an interconnectedness between self and universe.

dresden_codex

The Dresden Codex, one of the surviving folding-screen books of the Maya. Concerned with the 260-day ritual counts. Days are divided up in various ways, with divisions associated with different gods.

References:

Clendinnen, I. (2003). Ambivalent conquests: Maya and Spaniard in Yucatan, 1517-1570. Cambridge [u.a.: Cambridge University Press.

Coe, M. D. (1992). Breaking the Maya code. New York: Thames and Hudson.

Coe, M. D. (1999). The Maya. New York: Thames and Hudson.

Jenkins, J. M. (1994). Tzolkin: Visionary perspectives and calendar studies. Garberville, CA: Borderland Sciences Research Foundation.