Pregnancy Week by Week

Pregnant Week 21

Week 21

Your Baby

Your little one is between 7½ and 8 inches in length now, measuring from crown to rump and weighs approximately 10 ½ ounces. Your baby is growing stronger every single week. He or she is testing new reflexes along with exercising muscles and joints.

The ossification process continues in your baby’s bones and they are becoming harder. More vigorous movements are happening now and as a result, you may notice more forceful activity inside your growing belly.

Movements are becoming more coordinated, particularly arm and leg movements, as these muscles strengthen and grow. Your baby is very active and has lots of room to move around. He or she can spin, wiggle and even somersault in the amniotic fluid.

Meconium (your baby’s very first stool) is collecting in his or her bowels. After your baby swallows amniotic fluid, the indigestible substances are filtered out and remain behind in the intestines. Meconium is waste material, composed of various secretions of the digestive tract including undigested amniotic fluid, mucus, shed skin cells and even a little lanugo (the fine hair that covers your baby’s body). This material is usually greenish black, thick, sticky and more or less resembles tar. Sometimes before or during the course of labor, the baby will pass meconium into the amniotic fluid, while still inside the womb. This usually happens when a baby is in distress for some reason and the majority of the time it occurs in babies at term (after 37 weeks). If the baby breathes the meconium into his or her lungs, it is called “meconium aspiration”. If this happens, it can very well cause the airways to become plugged, which leads to respiratory distress. Also, it can cause the lungs to become inflamed and infection may set in, leading to pneumonia.

Production of blood cells is called “hematopoiesis” and begins about the 6th week of pregnancy (or approximately 4 weeks after conception) in the yolk sac. As your baby has grown and developed, blood cell production has transitioned to the liver and spleen. Toward the time of delivery, your little one will finally be manufacturing blood cells in the bone marrow exclusively, which will continue throughout life.

Bone marrow is the sponge-like tissue inside certain bones. Your baby’s immune system is beginning to develop, as white blood cells are produced. White bloods cells (leukocytes) help fight infections and they aid in the immune process. White blood cell levels are elevated after birth, but slowly fall as time goes on. Your baby’s blood contains much fewer white blood cells than red ones, although your baby’s body can already increase production of white blood cells to defend itself against infection. Your baby is also storing iron for red blood cell production now. Newborn babies are born with an abundance of red blood cells because of the low oxygen environment of your womb. After delivery, the red blood cell count gradually diminishes to adult levels as your baby’s body adjusts to breathing air, with its high oxygen content.

Your Body

You’re over halfway to your due date this week! You may be able to feel the top of your uterus approximately ½ inch above your belly button now. Your waistline is officially just a memory and there’s no doubt about it: you’re showing these days. At the very beginning of your pregnancy, your uterus was close to the size of your fist or a pear. Did you know that your uterus will be close to 30 times bigger than its pre-pregnancy size by the time your due date arrives? That will make it about the size of a watermelon! Immediately following delivery, it will shrink down to the size of a large grapefruit and back to the size of a pear approximately six weeks later. Your body goes through so much during the nine months of pregnancy; it’s truly amazing!

Your baby is kicking and punching fairly vigorously this week, but the amniotic sac is still doing a good job cushioning these movements. Kicks and punches will soon become much stronger. If you haven’t felt your little one’s movement yet, you most likely will by the end of this week. It’s very possible you’ve felt these first movements called “quickening” for a while now, but thought you were imagining things. This is especially true if this is your first pregnancy. If you’re very alert, slim or if you’ve been pregnant previously, you may have been able to identify your baby in action for weeks already. Some women’s partners and family begin to feel soft movement now as well. Don’t despair if your loved ones haven’t been able to share in your excitement yet, because movements are growing more intense every week. As these slight movements become more consistent, they will be very reassuring to you. If you are concerned about your baby’s movements, contact your doctor or midwife without delay.

You may be wondering if exercise is still safe and if you can continue to exercise through the rest of your second trimester and into your third trimester. Regular exercise is very beneficial to your health, your baby’s health and also your energy level. Staying active throughout your pregnancy is important to help you look and feel your best.

Regular exercise can reduce some of your bothersome pregnancy symptoms including fatigue. Besides increasing your energy and stamina, moderate exercise may boost your mood, help with constipation, lead to a better night’s sleep and also improve your ability to cope with labor and delivery (don’t forget: a shorter second stage of labor!) Low-impact exercise is best during pregnancy, particularly walking and swimming.

Prenatal yoga is also an excellent choice. Avoid anything bouncy, jerky or strenuous, because your ligaments are much more relaxed and your center of gravity is shifting. You’re much more likely to lose your balance now and in the coming months. Also, overexertion can lead to overheating, dehydration and numerous unwanted complications.

Exercise wisely, avoiding such activities as: skiing, biking, skateboarding, rollerblading, scuba diving, water-skiing and exercises that require lying flat on your back. Make sure you speak with your doctor or midwife before stating an exercise program and if you have any problems or questions, don’t hesitate to call them.


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