During Which Stage of Pregnancy Do the Baby's Lungs Form?

Pregnancy lasts for 40 weeks and is divided into three terms called trimesters. Each trimester has different developmental milestones for the growing baby. The baby's lungs develop towards the end of pregnancy, in the third trimester.

  1. Basics

    • The lungs are usually the last organs to fully develop. Lung development starts around the 25th week of pregnancy. Though it is ideal to carry a pregnancy to full term, after 36 weeks the lungs are developed enough for a baby to survive outside the womb.

    Breathing

    • The fetus does not need lungs early in the pregnancy because it has the placenta. The placenta does the work of providing the baby with oxygen.

    Premature Labor

    • If a woman goes into labor too early, a steroid can be given to help the lungs develop more quickly.

    Newborns

    • When babies are in the womb their lungs are filled with fluid. By the time the baby is born most of the fluid should be gone so that the baby can take his first breath. By the time the baby is 90 minutes old, he should be taking 30 to 60 breaths per minute.

    Risks

    • Women who smoke during their pregnancy are putting their baby at risk of having lung problems.

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