Fetal Development: Your Baby's Digestive System - BabyCentre UK

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1. Pregnancy /
2. How your baby's growing

Fetal development: your baby's digestive systemMedically reviewed by Joseph Aquilina, Consultant obstetrician and gynaecologistWritten by Jenny LeachPhoto credit: Jonathan Dimes for BabyCenterIN THIS ARTICLE

• How does my baby's digestion develop in the womb?
• Can my baby digest anything before he's born?
• What are the milestones in my baby's digestive development during pregnancy?
• When will my baby do his first poo?
• What can I do during pregnancy to help my baby’s digestion develop?

How does my baby's digestion develop in the womb?

Your baby doesn't need a fully functioning digestive system until after he's born (Hill 2020). Until then, he gets all the nutrients he needs straight into his bloodstream through the placenta and umbilical cord (Moore et al 2019a). But as soon as he has his first feed after birth, his system will get to work digesting his milk and breaking down waste into poos and wees. There are plenty of full nappies to come! Advertisement | page continues below It all starts at five weeks of pregnancy, when a layer of cells on the underside of your baby's embryonic body rolls into a long tube. This tube will develop into his digestive tract (Chin et al 2017). About a week later, his early digestive tract begins to form into three main parts:

• The foregut, which becomes your baby's food pipe (oesophagus), stomach, liver, and pancreas.
• The midgut, which contains most of his small intestine and two-thirds of the large intestine.
• The hindgut, which contains the rest of the large intestine, the rectum, and the anal canal. (Hill 2020, Sanderson 2019)

By about eight weeks of pregnancy, the tract becomes a solid mass of developing cells and is no longer a tube (Moore et al 2019b). But by 10 weeks, small spaces develop within the tract, expanding to open up the tube again (Moore et al 2019b). In detail, here's how the parts of your baby's digestive tract develop: Foregut: oesophagus, stomach, liver, and pancreas By about seven weeks of pregnancy, your baby’s oesophagus and stomach is forming (Moore et al 2019b). Around this time, the developing liver appears as a small outgrowth, and the pancreas also starts budding (Moore et al 2019b). These organs support your baby's digestion. Advertisement | page continues below The liver helps to process many nutrients, breaks down fats, and filters out toxins (Hoffman 2019). The pancreas supplies digestive chemicals called enzymes that help to break food into smaller particles (Tang 2019). Your baby's liver grows quickly at this time because it temporarily becomes the source of his blood cells. That's until his bone marrow can take over the job later in pregnancy (Moore et al 2019b, Palis 2014). For this reason, by 11 weeks your baby's liver accounts for 10 per cent of his weight (Moore et al 2019b). Midgut: the intestines The intestines are the longest stretch of the digestive tract, and they grow very quickly. From seven weeks of pregnancy, there is limited space in your baby's tiny body so his intestines start to grow into the base of the umbilical cord (Moore et al 2019b). By 10 weeks, the small intestine has folded into loops to help create the huge surface area necessary to absorb nutrients from food processed in the stomach (Soffers et al 2015). On the inside of the small intestine, its lining forms finger-like projections called villi. These create an even greater surface area for absorbing nutrients (Chin et al 2017, Sanderson 2019). Advertisement | page continues below At 12 weeks of pregnancy, your baby's intestines start moving out of their temporary home in the umbilical cord and back into his abdomen (Moore et al 2019b). As the intestine folds, it also continues to lengthen, especially in the last trimester (Hill 2020). By the time your baby is born, his small intestine will be about half the length of an adult's (Hill 2020). That's about 5m long (Collins and Badireddy 2019, Hill 2020)! Hindgut: rectum and anus At first, your baby's rectum and anus and the structures that will form his bladder develop together (Moore et al 2019b). But by nine weeks of pregnancy, two separate regions develop: one for the urinary system and another for the anus and rectum (Moore et al 2019b). The rectum and anal opening are formed by 11 weeks of pregnancy (Bhatia and Bordoni 2019).

Can my baby digest anything before he's born?

Your baby doesn't need to use his digestive tract during pregnancy because of the nutrients he gets via the placenta, but he does start to swallow amniotic fluid by about 13 weeks (Moore et al 2019c). Any fluid he swallows passes out of his body as wee (Moore et al 2019c) and this waste is removed from the amniotic fluid via the placenta (Moore et al 2019a). By swallowing small amounts, your baby is helping to maintain healthy levels of amniotic fluid (Moore et al 2019a). Advertisement | page continues below By 13 weeks, your baby can also make sucking and chewing movements (Moore et al 2019c). And if his thumb happens to be near his mouth, he may latch onto it (Visembryo 2017). You may be able to catch a glimpse of him doing this during an ultrasound scan. By 26 weeks, your baby's intestines may be able to absorb particles into his bloodstream (Bhatia and Bordoni 2019). Some babies also develop the wave-like movements that help to move food along the digestive tract (peristalsis) (Sase et al 2004). As with swallowing, it's just practice for your baby's system at this point, since there's no actual food to move or absorb. During the third trimester, these wave-like movements in the digestive tract may happen more often (Sanderson 2019, Sase et al 2004) as your baby's gut matures (Sase et al 2005).

What are the milestones in my baby's digestive development during pregnancy?

Weeks pregnant	What's happening
5 weeks	Your baby's digestive tube starts to form.
7 weeks	His stomach, oesophagus, liver, and pancreas start to form.
8 weeks to 10 weeks	The digestive tube becomes a solid mass of developing cells before hollowing out into a tube again.
7 weeks to 11 weeks	The intestine takes up space in the umbilical cord, forming further loops and villi. These increase the surface area of both the intestine and its lining as it grows.
11 weeks	Your baby's rectum and anus form.
12 weeks	Your baby's intestine moves back into his abdomen from the umbilical cord.
13 weeks	Your baby can suck and swallow amniotic fluid, and meconium starts to build up in his gut.
26 weeks	Wave-like movements may be present in the intestine and some absorption may be possible.
28 weeks to birth	Peristalsis and absorption become more efficient.

When will my baby do his first poo?

At about the time your baby starts swallowing amniotic fluid, a substance called meconium begins to accumulate in his intestines (Taylor and Lavine 2014). Meconium is made up of amniotic fluid, mucus, skin cells, and other substances your baby has swallowed while in your womb (Taylor and Lavine 2014). Meconium usually stays in your baby's intestine until after birth, when it comes out as his first poo (Moore et al 2019b).

What can I do during pregnancy to help my baby’s digestion develop?

Make sure you go to your mid-pregnancy ultrasound scan at around 18 weeks to 21 weeks of pregnancy (NHS 2018). During this scan, your sonographer will get an overview of how your baby is developing. She'll check your baby's abdomen, and the amount of amniotic fluid surrounding him (FMF nd, NHS 2018, PHE 2018). Rarely, an unborn baby's digestive system may not be developing as it should, meaning he isn't swallowing enough fluid, or isn't passing enough urine (Beloosesky and Ross 2019). This may be reflected in the levels of fluid surrounding him, resulting in: Advertisement | page continues below

• polyhydramnios, where there's too much amniotic fluid (NHS 2017), or
• oligohydramnios, where there's not enough amniotic fluid (Beloosesky and Ross 2019, FMF nd)

The sonographer carrying out your scan should check for these conditions (FMF nd, PHE 2018). Sometimes, however, an imbalance in fluid doesn't signify anything and gets better by itself (Carter 2017, FMF nd, Moore et al 2019a). In either case, your midwife or doctor will offer you extra checks to ensure that you and your baby stay as well as possible (NHS 2017, PHE 2018). Learn more: Advertisement | page continues below

• Baby poo: a visual guide (photos)
• Your baby's poo: what's normal and what's not
• Fetal development timeline

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Sources

BabyCentre's editorial team is committed to providing the most helpful and trustworthy pregnancy and parenting information in the world. When creating and updating content, we rely on credible sources: respected health organisations, professional groups of doctors and other experts, and published studies in peer-reviewed journals. We believe you should always know the source of the information you're seeing. Learn more about our editorial and medical review policies.

Beloosesky R, Ross MG. 2019. Oligohydramnios. UpToDate. www.uptodate.comOpens a new window [Accessed January 2020] Bhatia A, Bordoni B. 2019. Embryology, gastrointestinal. StatPearls. www.ncbi.nlm.nih.govOpens a new window [Accessed January 2020] Carter BS. 2017. Polyhydramnios and oligohydramnios. Medscape. reference.medscape.comOpens a new window [Accessed January 2020] Chin AM, Hill DR, Aurora M, et al. 2017. Morphogenesis and maturation of the embryonic and postnatal intestine. Semin Cell Dev Biol 66:81-93. www.ncbi.nlm.nih.govOpens a new window [Accessed January 2020] Collins JT, Badireddy M. 2019. Anatomy, abdomen and pelvis, small intestine. StatPearls. www.ncbi.nlm.nih.govOpens a new window [Accessed January 2020] FMF. nd. Fetal abnormalities by system: amniotic fluid - oligohydramnios. The Fetal Medicine Foundation. fetalmedicine.orgOpens a new window [Accessed January 2020] Hill MA. 2020. Gastrointestinal Tract Development. University of New South Wales Embryology. embryology.med.unsw.edu.auOpens a new window [Accessed January 2020] Hoffman M. 2019. Human anatomy: picture of the liver. WebMD. www.webmd.comOpens a new window [Accessed January 2020] Moore KL, Persaud TVN, Torchia MG. 2019a. Placenta and fetal membrances. Chapter 7 in The developing human: clinically oriented embryology. 11th edition. Elsevier. Moore KL, Persaud TVN, Torchia MG. 2019b. Alimentary system. Chapter 11 in The developing human: clinically oriented embryology. 11th edition. Elsevier. Moore KL, Persaud TVN, Torchia MG. 2019c. Ninth week to birth. Chapter 6 in The developing human: clinically oriented embryology. 11th edition. Elsevier. NHS. 2017. Polyhydramnios. NHS, Health A-Z, Pregnancy and baby. www.nhs.ukOpens a new window [Accessed January 2020] NHS. 2018. 20-week scan. NHS, Health A-Z, Pregnancy and baby. www.nhs.ukOpens a new window [Accessed January 2020] Palis J. 2014. Primitive and definitive erythropoiesis in mammals. Front Physiol 5: 3. www.ncbi.nlm.nih.govOpens a new window [Accessed January 2020] PHE. 2018. NHS fetal anomaly screening programme handbook: valid from August 2018. Public Health England. assets.publishing.service.gov.ukOpens a new window [Accessed January 2020] Sanderson IR. 2019. Overview of the development of the gastrointestinal tract. UpToDate. www.uptodate.comOpens a new window [Accessed January 2020] Sase M, Miwa I, Sumie M, et al. 2004. Ontogeny of gastric emptying patterns in the human fetus. J Matern Fetal Neonatal Med 17(3): 213-7 [Accessed January 2020] Sase M, Miwa I, Sumie M, et al. 2005. Gastric emptying cycles in the human fetus. Am J Obstet Gynecol 193(3 Pt2): 1000-4 [Accessed January 2020] Soffers JHM, Hikspoors JPJM, Mekonen HK, et al. 2015. The growth pattern of the human intestine and its mesentery. BMC Dev Biol 15:31. www.ncbi.nlm.nih.govOpens a new window [Accessed January 2020] Tang JCF. 2019. How does a normal pancreas function? Medscape. www.medscape.comOpens a new window [Accessed January 2020] Taylor SA, Lavine JE. 2014. Meconium. In Fetal and neonatal secrets. 3rd ed. www.sciencedirect.comOpens a new window  [Accessed January 2020] Visembryo. 2017. Why are you left or right handed?/i> The Visible Embryo. www.visembryo.comOpens a new window [Accessed January 2020]Jenny LeachJenny Leach is an editor and writer specialising in evidence-based health content. Opens a new window Opens a new window Opens a new window

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