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18 Weeks Pregnant: Week by Week Pregnancy

Symptoms, Tips and Fetal Development


Welcome to pregnancy week 18. Here’s what’s happening this week in the world of baby growing and mama-body changes! 

Baby at 18 weeks pregnant

Your baby’s stats at 18 weeks: crown to rump is about 6 inches long and s/he’s tipping the (kitchen) scales at between 5.25-6.5 ounces. That’s big enough that you could be feeling some fetal movements, be they kicks, twists, punches, or flips. Also: baby hiccups! Later in your pregnancy your baby’s hiccups will shake your whole belly. If you’re not feeling your baby moving yet, those flutters are coming soon.

If you could peek at your baby’s teeny-tiny fingers and toes, you’d see fingerprints! His or her tiny bones are beginning to harden, in a process called ossification, with the leg bones, collarbone, and inner ear being the first to ossify. Speaking of the inner ear, your little can now hear, thanks to bone development and also the development of nerve endings getting connected with the ears. S/he’s tuning in to the sounds of your stomach rumbling and heart beating, and can be startled by loud sounds.

pregnancy week 18 embryo
Weekly development of a human fetus at 18 weeks pregnant.

Your body at 18 weeks pregnant

At 18 weeks pregnant, you’re probably sporting a bit of a belly – anyone on “bump watch” will surely be suspicious that you’re pregnant. Your uterus can be felt two finger widths or one inch below your belly button, and it’s possible you’ve picked up between 5-15 pounds by this point. If morning sickness has been a constant for you and you haven’t gained any weight, this is probably when you’ll start adding some pregnancy pounds. It’s recommended women gain 12-14 pounds in the second trimester.

The good news: You might be feeling extra frisky this trimester, now that the nausea has passed and all those hormonal changes have made your genitals ultra sensitive (the additional blood flow to the labia, clitoris, and vagina can make it easier to climax, hooray!). 

The bad news: Heartburn is a common ailment that could show up and stick around when you're 18 weeks pregnant. There are a number of tips and remedies to combat heartburn, including eating smaller meals, drinking peppermint or chamomile tea, avoiding trigger foods like tomato-based sauces and chocolate, and using antacids.

18 weeks pregnant ultrasound

Most women have an anatomy scan anytime between 18-20 weeks. The anatomy scan is a 2-D ultrasound that presents a flat profile of baby’s features and major organs, and also provides a chance to check your baby’s size, the location of your placenta, and the level of amniotic fluid. It’s also an opportunity for parents to learn the sex of their baby, assuming baby cooperates! If you don’t want to know the sex, be sure to let the ultrasound technician know so s/he doesn’t accidentally spoil the surprise. 

How big is my baby at 18 weeks?

three peppers, symbolizing the size of a 6 week embryo

At 18 weeks pregnant, your baby is the size of a pepper, on average measuring at 5.5 inches long and weighing on average at 7.4 ounces.

18 weeks is how many months pregnant? 

At this stage in your pregnancy, you are four months, 2 weeks (4m2w) pregnant. 

Common symptoms at 18 weeks pregnant

These are some of the most common symptoms women experience when they’re 18 weeks pregnant.

  • Pregnancy brain: Many women report feeling forgetful or absent-minded in pregnancy, in a phenomena sometimes called “baby brain.” Although there’s no scientific evidence to support the idea that pregnant women experience cognitive changes, it seems reasonable to think that a major life change like pregnancy could affect memory temporarily. As baby brain is a commonly-held belief throughout our society, it’s likely that women are aware of it and therefore more alert to any sign of forgetfulness.
  • Fast-growing hair and nails: Thanks to a hormone-fueled boost in circulation and metabolism, your nails and hair are likely growing at rapid rates. Elevated hormone levels also prevent you from shedding hair at the normal rate, which can lead moms to boast thick, shiny manes throughout their pregnancies. Hair growth could also start to occur in less opportune places (think face, back, and chest). For better or worse, all hair and nail changes retreat soon after delivery.
  • Leg cramps: Leg cramps are common in pregnancy, particularly in the second half, and can be caused by inadequate levels of calcium or potassium. Make sure you’re drinking a lot of water and sleeping on your side. And if you can, avoid standing for long periods of time. 
  • Mild anemia: Anemia occurs when you don’t have enough hemoglobin-rich red blood cells to carry oxygen to your body’s tissues. Anemia can cause tiredness, but unless it’s severe it won’t affect your baby.
  • Breast growth: Your breasts might might now be almost two cup sizes larger than before you got pregnant, with more visible veins. You might notice that veins in your arms and legs are becoming more visible.
  • Slight increase in vaginal discharge: Thanks to an increase in cell turnover, it’s normal to have milky, mild-smelling discharge throughout pregnancy. It’s believed to help protect the birth canal and maintain a healthy vagina. Use unscented panty liners and never douche during pregnancy.
  • Lower blood pressure: Your blood pressure drops slightly in the second trimester due to increased blood volume. This can cause you to experience dizziness when you stand up too quickly, or in hot weather, so take care.
  • Increased appetite: As nausea fades, you might be feeling hungrier. Pregnant women need about 300 additional calories per day (so not a lot, really!). Aim to use them on nutrient-rich foods that benefit fetal development (with a few treats now and then of course!).
  • Back pain: Lower back pain in pregnancy is common, caused by loosening ligaments and the curving of your spine to compensate for your shifting center of gravity.
  • Heartburn: The increased levels of estrogen and progesterone have relaxed the muscles in your body, including those in your digestive tract, slowing the emptying of your stomach. When your expanding uterus crowds your fuller belly, heartburn is often the result. If heartburn is or becomes an issue, try eating smaller, more frequent meals. 
  • Constipation: Again, the slowed, cramped digestive system is to blame. Make sure you’re drinking a lot of water and increase your fiber intake to counteract constipation.
  • Making balance adjustments: Your uterus is now positioned higher and more forward, shifting your center of gravity and causing you to unconsciously adjust your posture and the way you walk and stand. It’s possible your belly button has started to stick out a bit!
  • Skin pigmentation: Whether it’s a linea nigra on your belly, darkening areolas around your nipples, shading in your armpits and inner thighs, or melasma (aka chloasma, the mask of pregnancy) on your face, skin pigmentation is a common side effect of pregnancy. All will fade and most will completely disappear after pregnancy.
  • Red palms and soles: You could experience redness and itchiness on your palms and the soles of your feet, again courtesy of your hormones. For relief try soaking them in cold water or applying an ice bag, and avoid things like hot water baths and wool socks and gloves that might heat up your appendages.
  • Increased libido: Many women notice they feel “in the mood” more often during the second trimester. Unless your doctor says otherwise, sex is safe during pregnancy

Pregnancy checklist at 18 weeks pregnant

Here are a few things to know or do when you’re 18 weeks pregnant.

  • Sleep on your left side: If you haven’t already, start sleeping on your left side to allow for the maximum flow of blood and nutrients to the placenta. Side sleeping also enhances kidney production for better elimination of waste products and fluids, helping you to have less swelling in your ankles, feet, and hands. Don’t worry if you do wake up on your back or abdomen, just turn back to side. Some women find body pillows can help with side positioning. If sleeping on your side is not working for you, another option is to prop yourself up in a semi-upright position.
  • Feel OK about having sex: Many women (and men!) feel anxious about having sex as though it will harm the baby. Not to worry: unless you’ve been told otherwise by doctor or midwife, sex during pregnancy is safe and women who stay sexually active during pregnancy are less likely to deliver early. Your baby is safe in your uterus and way out of reach (don’t worry, s/he can’t see what’s going on). Some women experience mild contractions after an orgasm, but as these are not the kind that trigger premature labor they are not cause for concern.
  • Check out birthing classes: It's a good time to start thinking about birthing classes. Your healthcare provider can probably help direct you towards some birthing classes in your area. Many single moms worry that they can't take these classes without a spouse, but instead consider bringing a friend who can support you throughout the class and the birth. Learn more about the options for prenatal classes here.

What to Expect at 19 Weeks Pregnant

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