Week 18: Anatomy Scan Preparation - The Big Ultrasound

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The Most Detailed Look at Your Baby

Week 18 often marks the time when you'll have your detailed anatomy ultrasound, also known as the morphology scan or "20-week scan" (though it's typically performed between 18-22 weeks). This comprehensive examination provides the most detailed look at your baby's development so far and is one of the most exciting appointments for expectant parents⁵.

What the Anatomy Scan Reveals

During this scan, your healthcare provider will examine:

• Brain development and skull formation
• Heart structure and function (four-chamber view)
• Spine alignment and development
• Kidney function and bladder filling
• Limb development and movement
• Facial features and lip formation
• Placental position and function
• Amniotic fluid levels
• Baby's growth measurements

The technician will take numerous measurements to ensure your baby is growing appropriately and that all organs are developing normally. This scan can detect many structural abnormalities, though it's important to understand that no screening test is 100% accurate.

Gender Reveal Possibility

If you choose to learn your baby's sex, week 18 is typically when it can be determined with high accuracy. The external genitalia are now well-developed enough to distinguish between male and female anatomy, though baby's position can sometimes make visualization difficult⁶.

Some parents choose to keep the sex a surprise, while others are eager to know. There's no right or wrong choice – it's entirely personal preference. If you want to be surprised, make sure to tell your ultrasound technician before the scan begins!

Your Baby's Development This Week

Your baby now measures approximately 14.2 cm (5.6 inches) from crown to rump and weighs about 190 grams. The body proportions are becoming more balanced, with the head no longer dominating the overall size quite as much.

The nervous system is developing rapidly, with myelin (a protective coating) beginning to form around nerve fibers. This myelination process improves the speed and efficiency of nerve signal transmission and will continue well into childhood.

Vernix Caseosa Formation

Your baby's skin is beginning to be coated with vernix caseosa, a white, waxy substance that protects the skin from the amniotic fluid. This natural "moisturizer" prevents the skin from becoming waterlogged during the remaining months in the womb and provides protection during birth⁷.

Vernix is composed of water, proteins, and lipids, and it has antimicrobial properties that help protect against infection. Babies born prematurely often have more vernix, while those born after their due date may have less, as it's naturally absorbed as pregnancy progresses.

Your Physical Changes

As you approach the midpoint of pregnancy, you may notice:

• Your center of gravity shifting as your bump grows
• Possible back pain as your posture adjusts
• Increased appetite and specific food cravings
• Heartburn as your growing uterus puts pressure on your stomach
• Leg cramps, especially at night

Recipe: Nutrient-Dense Stuffed Bell Peppers

Ingredients

• 4 bell peppers, tops cut and seeds removed
• 1 cup cooked brown rice
• 1/2 lb lean ground turkey
• 1/2 cup diced onion
• 1/2 cup corn kernels
• 1/2 cup black beans, drained
• 1/4 cup shredded cheese
• 1 tsp cumin
• 1 tsp paprika
• Salt and pepper to taste

Instructions

1. Preheat oven to 375°F
2. Cook ground turkey with onion until browned
3. Mix turkey, rice, corn, beans, and seasonings
4. Stuff peppers with mixture, top with cheese
5. Bake for 25-30 minutes until peppers are tender
6. Complete protein and complex carbohydrates for steady energy

Sources:

1. ACOG Practice Bulletin. (2016). “Ultrasonography in pregnancy”
2. Efrat, Z., et al. (1999). “First-trimester determination of fetal gender”
3. Visscher, M.O., et al. (2005). “Vernix caseosa in neonatal adaptation”