You Can Talk to Them Now
Week 18 marks a turning point you may not have expected: your baby can hear you. The inner ear bones have hardened enough to transmit vibrations, and the auditory nerve is functional. The sounds your baby hears right now are mostly internal, your heartbeat, blood rushing through vessels, the gurgles of digestion, but external sounds, including your voice, are beginning to reach them too [1].
Some women feel self-conscious about this idea. Others immediately start narrating their day. There is no wrong response. What matters is that this is one of the first ways the person you haven't met yet is already learning who you are.
Your Baby This Week
Your fetus is now about the size of a bell pepper, measuring roughly 5.6 inches (14.2 cm) from crown to rump and weighing approximately 6.7 ounces [1]. The growth pace is accelerating.
Milestones this week:
- Hearing is now functional. The ossicles (tiny bones of the middle ear) have hardened, allowing vibration to transmit sound. Your baby can hear muffled versions of your voice and other external sounds [3].
- Myelin is forming. A fatty insulating substance called myelin is beginning to coat the nerve fibers throughout the nervous system. Myelin dramatically speeds the transmission of nerve signals and will continue developing well into the toddler years [4].
- Female reproductive anatomy is complete. If your baby is female, the uterus and fallopian tubes are fully formed by this week. The ovaries already contain millions of immature egg cells, more than she will ever use in her lifetime [3].
- The skeleton continues hardening. Ossification is ongoing in the legs, spine, and skull. Calcium from your diet continues to be incorporated into the developing bones [1].
Preparing for the Anatomy Scan
The anatomy scan (also called the Level II ultrasound or 20-week scan) can be scheduled as early as 18 weeks, though most providers and practices schedule it between 19 and 22 weeks to allow all structures to be adequately visible [2][5].
Here is how to prepare and what to expect:
Scheduling. If you haven't already scheduled your anatomy scan, call MomDoc now. The window is weeks 18 through 22. Waiting much past 22 weeks narrows the ability to see all structures clearly, as the baby grows larger and harder to image in full.
Before the appointment.
- Drink a moderate amount of water before your scan. A comfortably full bladder can help the sonographer get better images early in the exam.
- Eat a normal meal beforehand. There is no fasting required for the anatomy scan.
- Write down any questions you have. This is a long appointment and a good time to ask about placenta position, fluid levels, or anything else you've been wondering about.
What the sonographer is evaluating [2][5]:
- Brain, skull, and facial structures (lip, nose, eye orbits)
- Spine from top to bottom
- Four-chamber heart view and outflow tracts
- Abdominal organs: stomach, kidneys, bladder, umbilical cord insertion
- Arms, legs, hands, and feet
- Placental location and amniotic fluid volume
The sex question. Week 18 is late enough that sex can often be determined on ultrasound if the baby is cooperative. Tell your sonographer at the start whether you want to know.
If something needs a second look. Sometimes the baby's position makes it impossible to see a specific structure clearly. This is extremely common and almost never a sign that something is wrong. A follow-up scan or a brief re-scan at the end of the appointment is often all that's needed [2].
Your Body at Eighteen Weeks
- Definite fetal movement. By week 18, many women, particularly those who have been pregnant before, are feeling recognizable kicks and rolls. First-time mothers may still be in the "is that gas or the baby?" phase. Both are normal.
- Nighttime leg cramps. As blood volume increases and the expanding uterus puts pressure on leg veins, painful cramps in the calves may wake you at night. Gentle stretching before bed, staying well hydrated, and ensuring adequate magnesium in your diet can help reduce frequency.
- Nasal congestion. Pregnancy rhinitis (stuffy nose without illness) often peaks in the second trimester. Saline sprays and humidifiers are safe first-line options.
- Lower back discomfort. The relaxin hormone is loosening pelvic ligaments, which is necessary for birth but can cause achiness in the low back and hips. Supportive footwear and attention to posture help.
What MomDoc Wants You to Know
The anatomy scan is the most anticipated appointment of most pregnancies. The nerves you feel walking in are completely normal. The vast majority of anatomy scans come back with entirely reassuring findings, and for most families, the appointment is primarily memorable for being the first really detailed look at their baby's face.
Come prepared with questions. Come with your partner or support person if you'd like. And if you find out the sex, know that whatever you're feeling in that room, from surprise to grief to pure joy, has been felt in that same room by someone before you.