Week 18 of Your Pregnancy

Verywell / Bailey Mariner

Table of Contents
View All
Table of Contents

At 18 weeks pregnant, others may begin to notice that you're expecting. This week, you may be feeling your baby move, and you may get the opportunity to see your baby during an ultrasound.

18 Weeks Pregnant Is How Many Months? 4 months and 2 weeks

Which Trimester? Second trimester

How Many Weeks to Go? 22 weeks

Your Baby's Development at 18 Weeks

At 18 weeks, baby measures a little over 5 3/4 inches (14.7 centimeters) from the top of their head to the bottom of the buttocks (your doctor may call this measurement the crown-rump length).

The average height for a baby at 18 weeks from the top of their head to their heels (known as crown-heel length) is approximately 8 1/3 inches (21.2 centimeters). This week the baby weighs almost 8 ounces (222 grams).

At 18 weeks pregnant, your baby is about the length of baby shampoo
Verywell / Bailey Mariner  


Your baby-to-be is practicing their napping skills. The internal clock that regulates sleeping and waking throughout the day is developing and will become more organized as your baby continues to grow.

Nervous System

Baby is also beginning to form myelin. Myelin is a mix of fat and protein that insulates and protects nerve cells in the nervous system, including the brain and the spinal cord. It also helps messages travel along the nerve pathways faster.

Reproductive System

While your baby's reproductive system is still developing, at this stage, the doctor or ultrasound tech can determine the baby's sex visually with a high degree of accuracy.

Explore a few of your baby's week 18 milestones in this interactive experience.

Stay Calm Mom: Episode 4

Watch all episodes of our Stay Calm Mom video series and follow along as our host Tiffany Small talks to a diverse group of parents and top doctors to get real answers to the biggest pregnancy questions.


Your Baby's Ultrasound: What to Expect

Your Common Symptoms This Week

This week, you're more likely to look pregnant, and you have a better chance of feeling your baby move. But, as your waistline expands, you may also feel off-balance as you adjust to your changing body. Dizziness from a natural dip in blood pressure is also common during the second trimester.

Feeling Movement

Some expecting parents, especially those who have been pregnant before, may have already started to feel baby flutters. For many first-time parents-to-be, feeling those first little movements or kicks called quickening may begin this week. But not feeling baby move just yet doesn't mean there's anything wrong. Some pregnant people don't feel anything until week 20 or even later.

Baby Bump

Your uterus is continuing to expand, and it's making your pregnancy more and more visible. Of course, everyone's body is different. You may have a very obvious baby belly, or you may just have a little bump that's barely noticeable to others. You're more likely to have a bigger bump if you've been pregnant before.

Balance Issues

As your belly grows, your body shape and your center of gravity shifts. Add to that changes in your muscles and joints, and you can find yourself a little off balance. You may feel unstable, wobbly, and even begin to trip. Reaching forward can also become more difficult.

Low Blood Pressure

Some pregnant people see a natural dip in their blood pressure during mid-pregnancy. These slight changes are not typically dangerous. However, low blood pressure can lead to fatigue, dizziness, and feeling faint.

Not all those expecting have the mid-pregnancy dip. Blood pressure changes during pregnancy vary greatly depending on your health, history, and genetic background.

Self-Care Tips

You may want to learn how to combat dizziness this week. It's also a great time to think about doing something special for yourself.

Dealing With Low Blood Pressure

You may not feel any different, even if your blood pressure does drop a bit. But, if you feel a little dizzy or lightheaded, you can try:

  • Getting up slowly from a seated or lying position
  • Avoiding standing for long periods
  • Making sure your showers and baths are not overly warm
  • Drinking plenty of water

Dizziness could also be a sign of low blood sugar or anemia, so be sure to mention it to your doctor.

A Little Pampering

You've been going through a lot of physical and emotional changes in the last few months. If you can swing it, take a little break to do something for yourself. You could spend a few hours or a day with your friends or your partner at a spa or nail salon. A prenatal massage might be a nice splurge, but a hair cut, manicure, and pedicure can also get you feeling revived and reenergized.

Just be sure to let everyone who works with you at the spa or salon know that you're pregnant. Most treatments, such as manicures and hair coloring, are safe once you enter your second trimester, but limiting the use of chemicals and staying in a well-ventilated area is always safest. You can check with your doctor's office if you have questions about any treatments.

Of course, not everyone enjoys the salon. Maybe you would rather spend some quality time with your partner or friends at dinner or a movie. The important thing is to take time to do what makes you happy.

Your Week 18 Checklist

Advice for Partners

There’s a lot to prepare for before the baby arrives, including interviewing and ​choosing a doctor for your child. You can help start the search by getting some recommendations from family, friends, other parents, or even your own physician.

There are many things to consider when choosing a doctor. You may prefer the intimacy and specialization of private pediatric practices. Or, you may value the benefits of choosing a pediatrician affiliated with a medical care facility, such as easier electronic medical record referencing (for family history) and the convenience of scheduling several visits for members of the family all on the same day, in the same place.

Once you’ve narrowed your list of candidates, team up with your partner and schedule some doctor meet-and-greets. At these sessions, you can discuss basic issues, including appointment availability, weekend coverage, hospitals the practice is affiliated with, and what insurance they accept.

You’ll also want to come armed with more personal questions on topics such as:

These meetings are common practice (and are usually free), so don’t worry about pediatricians accommodating or charging for them.

At Your Doctor’s Office

You may be scheduled for prenatal testing this week.

  • The maternal serum screening or quad screen blood test is typically offered between 15 weeks and 22 weeks.
  • Amniocentesis, when recommended, is performed between week 15 and week 20.

Second Trimester Ultrasound

This week you may get to see your baby. The big, mid-pregnancy ultrasound will most likely take place between 18 weeks and 22 weeks.

This ultrasound goes by a few different names, such as:

  • Structural ultrasound
  • Anatomy screen
  • Level II (Level 2) ultrasound
  • Fetal anatomy survey
  • Second trimester ultrasound

This ultrasound provides your doctor with detailed information about your baby and your pregnancy. It includes an examination of the baby's body parts, including the:

  • Head
  • Face
  • Neck
  • Brain
  • Chest
  • Heart
  • Abdomen
  • Kidneys
  • Bladder
  • Spine
  • Arms
  • Legs
  • Reproductive organs

It also looks at and measures the umbilical cord, the placenta, and the amniotic fluid.

During this ultrasound, you can learn the sex of your baby or babies. If you don't want to know this information, be sure to tell your doctor and the ultrasound tech in advance.

Upcoming Doctor’s Visits

Your next routine prenatal visit will be around 20 weeks.

Special Considerations

Your doctor may recommend more detailed prenatal testing in certain situations. Two tests that are performed at or around 18 weeks or after are fetal echocardiogram and fetal blood sampling.

Prenatal Heart Ultrasound

A fetal echocardiogram is a special ultrasound of the baby's heart. The ultrasound uses sound waves to show the parts of the heart and how the heart is working. It also shows the blood flowing through the baby's heart and can pick up problems with the baby's heart rate or rhythm.

Your doctor may recommend this test if:

  • You already had a child born with a congenital heart abnormality
  • You or your partner have a family history of congenital heart disease
  • A prior ultrasound identified a possible heart issue
  • The baby's heartbeat is too fast or too slow
  • Genetic testing revealed a condition with a high risk of heart problems
  • You took a medication that could cause a heart issue
  • You had an infection that put the baby at risk
  • You have diabetes

This procedure is typically performed between 18 weeks and 22 weeks. It is similar to and as safe as a regular ultrasound.

Fetal Blood Sampling

Cordocentesis is a prenatal test where blood is removed from the umbilical cord to test the baby for anemia or other blood disorders. It is also a way for doctors to treat the baby for certain conditions since they can give medication or a blood transfusion directly to the baby.

This test may be recommended if the baby is at risk for severe anemia or another blood disorder. It is the only test that can get directly to the baby's blood and circulation. In the past, fetal blood sampling was also used to test for infections and chromosomal abnormalities. However, with advances in technology, safer prenatal diagnostic tests such as chorionic villus sampling (CVS) and amniocentesis are now much more common.

Fetal blood sampling is not without risks. So, your doctor will discuss the benefits and the possible complications with you. Complications include:

  • Bleeding from the puncture site
  • The baby's heart rate going down
  • Pregnancy loss

A Word From Verywell

At 18 weeks, your baby is growing and moving all around. This week, you may feel some of those moves and get to see your child demonstrate them on the ultrasound screen. If you don't get to peek inside the womb this week, you'll probably get the chance within the next few weeks.

15 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Oyer CE, Sung CJ, Friedman R, et al. Reference values for valve circumferences and ventricular wall thicknesses of fetal and neonatal hearts. Pediatr Dev Pathol. 2004;7(5):499-505. doi:10.1007/s10024-004-1117-6

  2. Kiserud T, Piaggio G, Carroli G, et al. The World Health Organization Fetal Growth Charts: A multinational longitudinal study of ultrasound biometric measurements and estimated fetal weight. PLoS Med. 2017;14(3):e1002284. doi:10.1371/journal.pmed.1002220

  3. Pan X, Taylor MJ, Cohen E, Hanna N, Mota S. Circadian clock, time-restricted feeding and reproduction. Int J Mol Sci. 2020;21(3):831. doi:10.3390/ijms21030831

  4. Girard NJ, Dory-Lautrec P, Koob M, Dediu AM. MRI assessment of neonatal brain maturation. Imaging in Medicine. 2012;4(6):613-32.

  5. MedlinePlus, Myelin. U.S. National Library of Medicine. U.S. Department of Health and Human Services National Institutes of Health.

  6. Chitayat D, Glanc P. Diagnostic approach in prenatally detected genital abnormalities. Ultrasound Obstet Gynecol. 2010;35(6):637-46. doi:10.1002/uog.7679

  7. Linde A, Georgsson S, Pettersson K, Holmström S, Norberg E, Rådestad I. Fetal movement in late pregnancy - a content analysis of women's experiences of how their unborn baby moved less or differentlyBMC Pregnancy Childbirth. 2016;16(1):127. doi:10.1186/s12884-016-0922-z

  8. Takeda K, Shimizu K, Imura M. Changes in balance strategy in the third trimester. J Phys Ther Sci. 2015;27(6):1813-7. doi:10.1589/jpts.27.1813

  9. Salles GF, Schlüssel MM, Farias DR, et al. Blood pressure in healthy pregnancy and factors associated with no mid-trimester blood pressure drop: A prospective cohort study. Am J Hypertens. 2015;28(5):680-9. doi:10.1093/ajh/hpu204

  10. American Academy of Pediatrics. Ten Things Physicians and Patients Should Question. American Board of International Medicine (ABIM) Foundation.

  11. Bethune M, Alibrahim E, Davies B, Yong E. A pictorial guide for the second trimester ultrasoundAustralas J Ultrasound Med. 2013;16(3):98–113. doi:10.1002/j.2205-0140.2013.tb00106.x

  12. American College of Obstetricians and Gynecologists. Ultrasound in pregnancy. Practice Bulletin No. 175Obstet Gynecol. 2016;128: e241–56. doi:10.1097/aog.0000000000001815

  13. MedlinePlus. Fetal Echocardiogram. U.S. National Library of Medicine. U.S. Department of Health of Human Services National Institutes of Health.

  14. Donofrio MT, Moon-grady AJ, Hornberger LK, et al. Diagnosis and treatment of fetal cardiac disease: A scientific statement from the American Heart Association. Circulation. 2014;129(21):2183-242. doi:10.1161/01.cir.0000437597.44550.5d

  15. Berry SM, Stone J, Norton ME, Johnson D, Berghella V. Fetal blood sampling. Am J Obstet Gynecol. 2013;209(3):170-80. doi:10.1016/j.ajog.2013.07.014

Additional Reading

By Holly Pevzner
Holly Pevzner is an award-winning writer who specializes in health, nutrition, parenting, and family travel.