At 16 weeks your baby is about 17.5 cm and 110 grams — avocado-sized. The ears have reached their final position on the sides of the head, and hearing has begun — even if it will take months to sharpen.
The short answer: the ears are in their final position and the fetus can begin registering sound, starting with the sounds carried through your own body — your heartbeat, digestion and voice. The neck has lengthened enough to hold the head more upright, and constant small movements are happening, though most women cannot feel them yet. Left-side sleeping only becomes specifically relevant in the third trimester, not now.
Your baby this week
Hearing is developing rapidly. The bones of the inner ear are formed and the ears have moved into their final position on the sides of the head — earlier in development they sat lower and further forward. Sound reaches the fetus mostly through the transmission of your own body rather than through the air, so your heartbeat, digestive sounds and voice are what is heard first and most clearly.
The neck has lengthened and strengthened enough that the head can be held more upright rather than tipped forward onto the chest. Muscle tone is developing fast, and the fetus is constantly moving — stretching, flexing, even doing small flips and kicks. Surrounded by a comparatively large volume of amniotic fluid, most of this motion does not translate into anything you can feel yet.
Your body this week
The uterus is now roughly halfway between your pubic bone and your navel — measurable progress that many care providers start recording as fundal height from around this point or soon after. Breasts may have grown a full cup size by now, driven by the same hormones preparing them for lactation later.
If you are going to feel the first flutters of movement, this is the earliest realistic point — though it is just as normal to feel nothing yet, especially in a first pregnancy. It is often described as bubbles, a light tapping, or butterflies rather than a clear kick, and it is easy to mistake for digestion until you learn to recognise it.
Tests and appointments
This week sits inside the quad test window if first-trimester screening was missed. Some care providers also begin measuring fundal height at routine appointments from around now, tracking growth in centimetres against the number of weeks.
✅ Worth doing this week
- Talk and sing to your bump — hearing is developing and your voice is one of the first things heard clearly
- Note any flutters, even ones you are not sure about — the pattern becomes clearer over the coming weeks
- Get properly measured for a bra again if the last fitting was more than a few weeks ago
- Do not force left-side sleeping yet — it matters later, not at 16 weeks
- Ask about the quad test if earlier screening was missed and the window is closing
When to call your doctor
Call the same day if: you have bleeding, severe or one-sided abdominal pain, a severe headache with visual disturbance or sudden swelling of the face and hands, fainting, a temperature above 38°C, or fluid leaking from the vagina.
FAQ — 16 weeks pregnant
Can the baby hear me at 16 weeks?
Hearing is just beginning, and it will keep improving for months — the fetus is not yet responding reliably to sound, but the machinery is now in place. Your voice, heartbeat and digestion are the sounds heard most, since they travel through your body rather than through amniotic fluid and air. External sounds become clearer from around 24–26 weeks.
Is it normal to feel nothing at 16 weeks?
Completely normal. First movements — quickening — are typically felt between 16 and 24 weeks, and first-time mothers usually feel them later than women who have been pregnant before, partly because they do not yet recognise the sensation. If this is not your first pregnancy, you may already notice occasional light flutters; if it is, most women feel nothing definite for a few more weeks yet.
What does the quad test check for at 16 weeks?
If it has not already been done, this is squarely within the 15–20 week window. It screens for Down syndrome, some other chromosomal conditions and neural tube defects using four blood markers, and — like every screening test — returns a probability rather than a yes-or-no answer.
Which side should I sleep on at 16 weeks?
Whichever is comfortable. The advice to favour the left side specifically becomes relevant from the third trimester, once the uterus is large enough to compress the vena cava when you lie flat on your back — not now, when the uterus is still small. There is no need to force a side this early, though building the habit gradually is reasonable if you find it easy.
Week 16 at a glance
At 16 weeks your baby is about 17.5 cm and 110 grams, with the ears in their final position and hearing beginning — starting with sounds carried through your own body. The neck has strengthened enough to hold the head more upright, and constant small movements are happening even though most women cannot feel them yet. Fundal height often starts being tracked around now, and the quad test window is still open if earlier screening was missed. Left-side sleeping is not yet relevant — that becomes important in the third trimester.
Inside Baby Novum: log the first uncertain flutters as they happen, and the app carries that history forward into structured kick counting once a daily pattern is established later in pregnancy.