Practice breathing in the womb is also known as “fetal breathing movements” (FBM). Practice breathing is essential for fetal lung development and helps your baby prepare for life outside the uterus. In this post, you’ll learn “when are babies lungs fully developed,” “when are lungs developed in fetus,” the lung development stages/stages of lung development, steroids for lung development, babies born with the cord around their necks, and much more!
Lung Development: When Lungs Develop in Fetus
Lungs begin to develop at 3 weeks of pregnancy and continue through each trimester.
“Development of the lower respiratory tract begins on day 22 and continues to form the trachea, lungs, bronchi, and alveoli” [1].
Some maternal health professionals believe a baby’s lungs are “fully” developed at 36 weeks, or 9 months pregnant. By this, they mean that, by 36 weeks, your baby’s lungs are formed enough to take their first breath. However, complete maturation of the lungs does not take place until a child is approximately 8 years old [1].
Regarding induction of labor, some OB-GYNs and midwives are even becoming acknowledging that when a baby is ready to be born, studies indicate that the baby’s lungs reach a point of maturation before releasing hormone signals into the amniotic fluid, which contributes to the initiation of labor at term [2].
Lung Development: How Lungs Develop
During pregnancy, your baby gets oxygen from your bloodstream through the placenta and the umbilical cord.
at 3-6 weeks of pregnancy:
At 3-6 weeks gestation, your baby’s lower respiratory tract begins to develop. A small pouch of tissue called the lung bud is created from the front wall of the tube that will become your baby’s esophagus.
Over the next week, the single bud will split into two separate buds (one for each lung), and the trachea (windpipe) will start to form between them.
By the end of 6 weeks, your baby’s larynx, trachea, lungs, lobes of the lungs, and bronchopulmonary segments have formed! (Aka, the basic structures of the respiratory system).
from 5-18 weeks:
From 5-17 weeks, this stage of fetal lung development is primarily responsible for generating the bronchial tree. By the end of week 16, your baby will have their first 20 generations of the respiratory tree!
At 17 weeks of pregnancy, your baby’s lungs have developed their main bronchioles, cartilage, and smooth muscle. However, the respiratory bronchioles have not developed yet. Therefore, infants born at this stage are unable to facilitate gas exchange and are unable to survive [1].
At about 18 weeks, the smallest tubes (bronchioles) start to develop at the tips of the branches. At the end of these tiny tubes, respiratory sacs that eventually form the alveoli begin to appear.
The alveoli are where the lungs and the blood exchange oxygen and carbon dioxide during the process of breathing in and breathing out.
From 24-40 weeks:
From 24 weeks of pregnancy on (until your child is about 8 years old) these respiratory sacs grow and multiply, adding more surface area for the exchange of oxygen and carbon dioxide.
Starting at 24 weeks, they start making a substance called surfactant, which coats the alveoli and keeps them inflated when there’s not a lot of air in the lungs (when exhaling, for example).
Adequate surfactant production is not until about 35 weeks, so infants born at that time have a much higher likelihood of independent breathing and survival than those born at 24 weeks.
By 40 weeks, your baby has about 150 million alveoli in his lungs, ready to take over the job of breathing once he’s born. By the time your child is eight years old, he will have another 150 million, which is the same number as you!
What is Practice Breathing?
Practice breathing is important for lung development and preparing for life outside of the uterus. Practice breathing can start as early as 10 weeks.
Between 24-28 weeks of gestation, fetuses practice breathe about 14% of the time [3]. Then, by 34 to 40 weeks practice breathing increases to about 30% of the time [4].
Are Hiccups Practice Breathing?
Your baby’s ability to hiccup is a positive indication that they are able to do practice breaths in your womb.
Hiccups also are a sign that the nerves that control your baby’s diaphragm are developing normally and communicating with baby’s brain.
What Does Practice Breathing Feel Like?
You cannot feel your baby practice breathing but you can feel when your baby has the hiccups. Your baby’s hiccups feel like a consistent jerking motion in the same spot of your belly.
Fetal Lung Development Milestones:
6 weeks: Lung bud develops
7 weeks: Lung bud branches into two buds, one for each main air tube (bronchus)
8 weeks: More air tubes (bronchi) start to form in the lungs
10 weeks: Breathing movements begin
18-26 weeks: Bronchi brand into smaller tubes (bronchioles) which start to expand
24-28 weeks: Now, your baby spends about 10-20% of the time practice breathing amniotic fluid
26 weeks and beyond: Respiratory sacs develop at the end of each outer bronchiole. They continue to grow, multiply and become coated in protective surfactant.
28 weeks: Gas exchange may be possible which is necessary for survival
30 weeks+: Your baby now spends 30-40% of its time practice breathing amniotic fluid
35 weeks: There is usually enough surfactant coating the maturing respiratory sacs (alveoli) to support lung function at birth.
40 weeks: There are now 150 million alveoli in the lungs, and another 150 million will form during childhood.
Is Practice Breathing a Sign of Labor?
There is evidence to suggest a lack of practice breathing may be a predictor of labor. As labor approaches practice breathing decreases. This sign has also been used to predict preterm labor [5].
But, does it make sense to have an induction or schedule a cesarean for lacking practice breathing alone?
There isn’t any evidence or reasoning to suggest that induction of labor or a scheduled cesarean is helpful or necessary for lacking practice breathing, even if the umbilical cord is also around your baby’s neck.
What if the umbilical cord is also around my baby’s neck?
Remember, your baby isn’t breathing to survive through their lungs yet! Their oxygen is coming from your bloodstream through the placenta and the umbilical cord. Did you know that 1/3 of babies are born with their umbilical cord around their neck? [6]
A baby’s first breath doesn’t occur until after the baby is born. Therefore, the OB or midwife simply unwraps it right before handing the baby to you, or even once your baby’s head is born.
An umbilical cord around your baby’s neck rarely causes complications, but if it is tight enough to restrict blood flow and impact practice breathing, there will also be signs of hypoxia and non-reassuring fetal well-being through a non stress test and biophysical profile.
The biophysical profile generally lasts 30-minutes and uses ultrasound to assess fetal heart rate, fetal breathing movements (practice breathing), fetal tone, amniotic fluid volume, and fetal movements. A scoring system is used when evaluating these 5 areas to determine if your baby is “reactive” or “nonreactive.”
If your baby is struggling at the time these tests are done, there will be multiple non-reassuring signs. If this is the case, consulting on the benefits, risks, and alternatives for interventions should occur following these tests.
However, if an OB or midwife is recommending an induction or a cesarean because of not seeing practice breathing for 20-30 minutes when the baby is only doing it 30-40% of its time by 30 weeks+, brining them into the world earlier than when they are ready likely will not help a baby with further developing lungs in-utero.
How Does a Baby Take Their First Breath?
During pregnancy, your baby’s lungs are filled with amniotic fluid and during a physiologic birth, contractions in labor drive the fluid outside the lungs, fetal adrenaline stimulated cells to stop secreting lung fluid and to start reabsorbing it, and the vagina is a tight passage that helps squeeze the amniotic fluid out of their lungs, assisting them in taking their first breaths and avoiding ‘wet lung,’ also known as acute respiratory distress syndrome.
Compared to infants exposed to labour, infants born by caesarean section are more likely to retain more liquid in their lungs and this may limit the amount of air entering into their airways at the first breath [7, 8].
Now, as I said, if there are other signs of distress in addition to this, then that is a different story of a baby who may be showing signs that they are at risk of stillbirth and consulting on the benefits, risks, and alternatives for interventions should occur following these tests.
When Do Babies Need Steroids for Lung Development?
Babies born prematurely (before 37 weeks of pregnancy) can have trouble breathing if their lungs are not sufficiently developed.
Steroids used between 25 and 33 weeks of pregnancy, steroids can improve lung development and newborn outcomes for those who are at risk of being born prematurely. This gives many preterm babies a much better chance of survival.
“Up to half of babies born before 28 weeks, and a third of babies born before 32 weeks, have problems breathing and many babies do not survive [9]. Others may become disabled due to the lack of oxygen they suffer because of the breathing difficulties experienced at birth” [9].
“Women who may be at risk of giving birth prematurely can be given corticosteroids to prevent their babies from having trouble breathing once they are born. Corticosteroids are anti-inflammation medicines that help the baby’s lungs mature before being born. They are usually given to women at risk of early labour, typically as two injections, though they can also be given before planned preterm birth and in some cases a repeat course can be given” [9].
Evidence shows that corticosteroids:
- Reduce perinatal and neonatal deaths (numbers of stillbirths and babies dying in the first 28 days of life) [9]. Without antenatal steroid treatment, about 10 out of 100 preterm babies die within a few weeks of being born [10]. With antenatal steroid treatment, about 7 out of 100 preterm babies die within a few weeks of being born [10].
- Lessen the likelihood of serious breathing problems in the first hours of life [9]. Without antenatal steroid treatment, about 12 out of 100 preterm babies have bleeding in the brain [10]. With antenatal steroid treatment, roughly 6 out of 100 preterm babies are affected [10].
- Have little to no effect on a baby’s birth weight [9]
- Reducing the risk of bleeding in the brain [10]. Corticosteroid treatment prevents this kind of bleeding in about 6 out of 100 children [10].
- Reduces the risk of a serious bowel condition called necrotizing entercolitis (NEC) [10]. Corticosteroid treatment prevents NEC in about 3 out of 100 preterm babies [10].
Warning Signs of Preterm Labor
Call your OB or midwife right away if you notice any of the following signs of preterm labor:
- More vaginal discharge than usual
- A change in the type of discharge – like if you’re leaking watery fluid or if your discharge becomes watery, mucusy, or bloody (even if it’s pink or just tinged with blood)
- Any vaginal bleeding or spotting
- Abdominal pain that feels like menstrual cramps, or having more than four contractions in one hour (even if they don’t hurt)
- Increased pressure in your pelvic area (a feeling that your baby is pushing down)
- Lower back pain, especially if it’s dull or rhythmic, or you didn’t previously have back pain
These symptoms can be confusing because some (such as pelvic pressure or low back pain) are common during pregnancy, and sporadic early contractions may be Braxton hicks contractions.
Check out: The Early Labor Signs You Need to Know
Still, it is better to be cautious! Call your OB or midwife right away if you have any unusual symptoms during your pregnancy.
How to Help Fetal Lung Development?
Nutrition plays a key role in fetal lung development [11]. Additionally, the influence of nutrition on lung growth also continues in early infancy and childhood.
Researchers have found that the most important nutrients for baby’s prenatal lung development are vitamins A, D, C, and E, selenium, and the omega-3 fatty acid, DHA [11, 12].
Beef, eggs, fish, sweet potatoes, carrots, spinach, and mango are all excellent sources of vitamin A.
For vitamin D, choose fortified milk and cereals and fatty fish like salmon.
Exceptionally high sources of vitamin C include oranges and orange juice, and strawberries. Other good sources include mango, bananas, broccoli. pineapple, clams, blueberries, okra, and more! One study found that a daily supplement of 500 mg vitamin C during pregnancy reduced abnormalities in neonatal pulmonary function and was associated with reduced relative risk of wheezing at 1 year of age by 56% [12].
Leafy green vegetables, whole grains, and nuts have plenty of vitamin E.
Seafood and walnuts are also good sources of selenium.
Fish is the best source of omega-3 fatty acids. But ensure you avoid eating high-mercury fish during your pregnancy.
Questions or Comments?
If you have any questions or comments, please leave them below👇🏻
Talk soon, mama!
– Katelyn Lauren
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References:
[1] Rehman S, Bacha D. Embryology, Pulmonary. [Updated 2022 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK544372/
[2] Mendelson, C. R., Montalbano, A. P., & Gao, L. (2017). Fetal-to-maternal signaling in the timing of birth. The Journal of steroid biochemistry and molecular biology, 170, 19–27. https://doi.org/10.1016/j.jsbmb.2016.09.006
[3] Natale R, Nasello-Paterson C, Connors G. Patterns of fetal breathing in the human fetal breathing during the last 10 weeks of gestation. Am. J. Obstet. Gynecol. 1980;56:24–30.
[4] Patrick J, Campbell K, Carmichael L, Natale R, Richardson B. Patterns of human fetal breathing during the last 10 weeks of pregnancy. Obstet. Gynecol. 1980;56:24–30.
[5] Besinger, R. E., Compton, A. A., & Hayashi, R. H. (1987). The presence or absence of fetal breathing movements as a predictor of outcome in preterm labor. American journal of obstetrics and gynecology, 157(3), 753–757. https://doi.org/10.1016/s0002-9378(87)80044-3
[6] Peesay M. (2017). Nuchal cord and its implications. Maternal health, neonatology and perinatology, 3, 28. https://doi.org/10.1186/s40748-017-0068-7
[7] Koos BJ, Rajaee A. Fetal breathing movements and changes at birth. Adv Exp Med Biol 2014; 814: 89–101.
[8] te Pas AB, Davis PG, Hooper SB, et al.. From liquid to air: breathing after birth. J Pediatr 2008; 152: 607–611.
[9] McGoldrick E, Stewart F, Parker R, Dalziel SR. Antenatal corticosteroids for accelerating fetal lung maturation for women at risk of preterm birth. Cochrane Database of Systematic Reviews 2020, Issue 12. Art. No.: CD004454. DOI: 10.1002/14651858.CD004454.pub4.
[10] InformedHealth.org [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. Pregnancy and birth: Before preterm birth: What do steroids do? 2008 Mar 14 [Updated 2018 Mar 22]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279568/
More references:
[11] Arigliani, M., Spinelli, A. M., Liguoro, I., & Cogo, P. (2018). Nutrition and Lung Growth. Nutrients, 10(7), 919. https://doi.org/10.3390/nu10070919
[12] McEvoy C, Schilling D, Clay N, Jackson K, Go MD, Spitale P, et al. Vitamin C supplementation for pregnant smoking women and pulmonary function in their newborn infants. JAMA. 2014;311:2074–82.
DISCLAIMER: This post is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding you or your baby’s health. Please read my Medical Disclaimer for more info
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