Week 18: Your cute little greased piglet

How your baby's growing:
Head to bottom, your baby is approximately 5 1/2 inches long (about the length of a bell pepper) and she weighs almost 7 ounces. She's busy flexing her arms and legs — movements that you'll likely start noticing more and more. Her blood vessels are visible through her thin skin and her ears are now in position and stand out from her head. Myelin (a protective covering) is beginning to form around her nerves, a process that will continue for a year after she's born. If you're having a girl, her uterus and Fallopian tubes are formed and in place. If your baby is a boy, his genitals are noticeable, though he may hide them from you during an ultrasound.

This is a big week for their baby skin. There are now two distinct layers—the epidermis (or the surface skin) and dermis. Currently, their skin is covered with a greasy, waxy, cheese-like substance, known as vernix caseosa. Sure, it sounds pretty nasty, but this mixture of fatty secretions covering your little swimmer from head to toe is the best way to protect their oh-so-thin skin from bruising and abrasions as well as chapping caused by amniotic fluid exposure (and your little one is swimming in that stuff!). Still don’t like the fact your little darling is currently slathered in fatty cream like a greased pig? Well, you know the birthing process? Where you have to push something the size of a watermelon out a hole the size of a grape? That adorable little greased piglet would have a lot harder time getting through the birth canal without the vernix caseosa. Fun fact for momma’s with baby girls: it’s a uterus within a uterus! Your little girl will have developed a uterus and vagina canal by the end of this week.

How your life's changing:
Bigger, more comfortable clothes are a must now as your appetite and waistline increase. Look for specially designed maternity clothes that can accommodate your expanding belly.

You may have heard that you should avoid lying on your back during your last two trimesters. Here's why: When you lie flat on your back, your uterus can compress a major vein (called the inferior vena cava) that returns blood from the lower half of your body back to your heart. Lying on your side (or even partially tilted to the side), particularly your left side, prevents this compression and improves your blood flow. Try placing a pillow behind you, or under your hip or leg for comfort.

Your cardiovascular system is undergoing dramatic changes, and during your second trimester your blood pressure is probably lower than usual. Don't spring up too fast from a lying or sitting position or you might feel a little dizzy.

If you haven't already, you'll probably have an ultrasound done sometime this trimester (usually between 16 and 20 weeks). This painless procedure helps your practitioner check how your baby's growing, screen for certain birth defects, check the placenta and umbilical cord, determine whether the due date you're working with is accurate, and see how many babies you're carrying. During the exam, you might see your baby moving around or sucking her thumb. Bring your partner along, and be sure to ask for a printout for your baby's first photo album!