The upper limbs are well differentiated into forearms, wrists, hands, and fingers; these develop at a faster rate than the lower limbs, a feature that continues even after the birth.
To help your baby's lungs expand and develop in preparation for breathing, the chest wall must be fully bathed in amniotic fluid.
Your baby's lungs continue to branch and divide. The cells lining the airways constantly produce fluid that leaves the lungs when your baby makes breathing movements. The release of this fluid is regulated by the vocal cords within the larynx.
In addition to fluid, the lungs have glands that produce mucus. Cells with tiny hairlike structures, known as cilia, have appeared that help move the mucus. This production of mucus is important once the baby is born to prevent the constant flow of air from drying the lining of the lungs, to trap dust particles, and to act as a barrier to infection.
Because the gut is still very immature, the gradual increase in amniotic fluid is due to the relatively low frequency of fetal swallowing. By 37 weeks your baby will be swallowing 1.75 pints (almost a liter), half of the total amniotic fluid volume, each day.
In this close-up the baby's left arm and chest wall can be seen. Because the skin is almost transparent the ribs are easy to see. They are very soft at this stage and still predominantly made of cartilage.
Focus On... Relationships
You may be taken aback by a sudden increase in your libido. Often, in the second trimester, women find that they feel far more energetic and sexy. The increased blood flow to the pelvic area combined with an increased lubrication of the vagina means that, in theory, having sex can be better than ever.
High levels of progesterone and estrogen make your breasts and vagina super sensitive so expect to become more easily aroused during foreplay. You may also find that you orgasm more quickly than usual. The uterus tightens when you orgasm, so be prepared for this.
Your partner may be delighted by this up-turn in events, as well as approving of a beautiful rounded body to explore, but if he isn't responding positively, talk to him about how he's feeling.