Pregnancy Week 29 – The Baby’s Progress

By the time you have reached pregnancy week 29 your baby’s lungs will have developed small airways and air sacs known as ‘alveoli’. One of the most important developments with the lungs to ensure your baby is capable of breathing outside of the womb is a substance called ‘surfactant’ which is now beginning to be produced.

Pregnancy at 29 Weeks – Lung Development

Pulmonary surfactant is a complex mixture of surface-active lipoproteins that maintain a low surface tension of the lungs during expansion and contraction resulting in the stability of the air sacs and airways of the lungs. It is coated around the lung’s internal surfaces to prevent them from sticking together in the deflated state when exhaling. The progressive loss of surfactant would lead to fatal lung collapse and suffocation so it is absolutely critical to the survival of all mammalian species. The highest cause of premature birth fatality comes from an infants inability to self sustain their own breathing prior to the production of surfactant.

If a baby is suspected to be born prematurely then the mother will be given a steroid injection in order to stimulate the baby’s lungs to begin producing the substance. If the baby is born expectantly early then they will be placed in intensive neonatal care and given artificial surfactant and breathing aid until their lungs have managed to mature sufficiently. The surfactant is normally produced and secreted by the alveolar cells within the lungs and are also responsible for regenerating the lungs and aiding gas exchange. This week your 29 week fetus will now have advanced, spontaneous, rhythmic chest breathing motions that are now controlled by the brain, along with the baby’s body temperature.

The growth of the placenta, at this stage, is beginning to slow down although it still receives around 400 ml (14fl oz) of blood from your circulatory system every minute enabling it to continue providing essential life support to the infant by exchanging nutrients, gases and waste products. The placenta is always working hard to ensure the well being of your baby by preventing any harmful substances and toxins from entering from the mother’s bloodstream into the baby’s lifeline.

By the end of pregnancy week 29 your rapidly maturing baby will now have an expanding waistline of his own as his abdomen begins filling out with all the fat deposits that are now being distributed throughout the body. He will now measure around 16.75” (42.5cm) and weigh in at approximately 2.9 lbs (1.32 kg).

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(See 29 Weeks Pregnant – The Mother’s Progress)

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