Baby at 27 Weeks Pregnant: Development & Milestones

Week 27 stopped me in my tracks in a way I did not see coming. Not because something dramatic happened — nothing dramatic happened. It was just that somewhere between the kicks and the hiccups and the realization that my baby was blinking in there, it became very real in a different way than it had been before.

If you are at 27 weeks right now, you are in the final stretch of your second trimester. Your baby has crossed into territory that feels genuinely remarkable — and understanding what is actually happening inside gives you something to hold onto that is bigger than any symptom or worry.

This is a week worth knowing about. Let me walk you through it.

For the full context of how fetal development connects to everything else happening in your pregnancy right now — your nutrition, your prenatal appointments, your mental health — the complete guide to being pregnant at 27 puts it all in one place.

How big is your baby at 27 weeks

At 27 weeks your baby weighs roughly 900 grams — just under two pounds — and measures around 36 to 37 centimeters from head to heel. The standard size comparison is a head of cauliflower, which sounds almost absurdly large when you think back to the poppy seed of week 4.

The growth rate from here accelerates. Your baby will roughly double in weight between now and week 36. The weeks ahead are primarily about fat accumulation, lung maturation, and brain development — which is exactly as remarkable as it sounds.

What your baby can do at 27 weeks

This is the part that genuinely gets me every time I think about it.

Your baby can open and close their eyes. The eyelids — which fused shut around week 10 to protect the developing retinas — have reopened. Your baby is blinking inside you. They can perceive the difference between light and dark, and research suggests they will turn toward a bright light directed at your belly.

Your baby is dreaming. Rapid eye movement sleep — the stage associated with dreaming — has been detected in fetuses at this stage of development. We cannot know what they dream about, obviously. But the brain activity is there.

Your baby has a regular sleep cycle. They cycle through active and quiet periods roughly every 20 to 40 minutes. Those stretches where you feel nothing followed by a sudden flurry of movement are not random — they reflect your baby’s actual sleep and wake states.

Your baby hiccups. If you feel a rhythmic, repetitive small movement that is different from a kick — steady and regular, almost like a pulse — that is most likely hiccups. Completely normal, often happens multiple times a day, and caused by the diaphragm contracting as the baby practices breathing movements.

Your baby can hear you. The auditory system is developed enough at 27 weeks that your baby is responding to sound. Your voice — specifically — is the most familiar sound in their environment. Research on newborn recognition of the mother’s voice is rooted in exactly this developmental window.

Brain development at 27 weeks

 

The brain is where the most significant activity is happening at 27 weeks. The cerebral cortex — the part of the brain responsible for thought, memory, language, and consciousness — is developing its characteristic folds and grooves during this period. Those folds, called sulci and gyri, dramatically increase the surface area of the brain and are directly linked to cognitive capacity.

Synaptic connections are forming at a rate that is genuinely difficult to comprehend. The brain is wiring itself. Every sound your baby hears, every sensation they experience, is contributing to that process.

This is part of why nutrition at this stage matters so much — specifically DHA, the omega-3 fatty acid found in fatty fish and algae-based supplements. DHA is a primary structural component of brain tissue and is being incorporated at high rates during the third trimester. It is one of the reasons prenatal nutrition recommendations don’t ease up in the second half of pregnancy.

Lung development at 27 weeks

The lungs are the last major organ system to fully mature, and at 27 weeks they are still in active development. The air sacs — alveoli — are forming, and the cells lining them are beginning to produce surfactant, the substance that prevents the lungs from collapsing when air enters them after birth.

A baby born at 27 weeks is considered very preterm but has a survival rate of around 90 percent with modern neonatal care. The lungs are functional enough to work with medical support, though they would need assistance initially.

This is not something to worry about if your pregnancy is progressing normally. It is simply worth knowing because it puts into context how much is happening in these weeks — and why full-term delivery gives your baby’s lungs the time they need to complete their development without intervention.

What you are feeling at 27 weeks

The physical experience of week 27 is distinct from earlier in pregnancy. Here is what is common at this point.

Movement is stronger and more noticeable. Those early flutters of weeks 18 to 20 have become definitive kicks, rolls, and jabs. You may see your belly visibly move. Some of those movements are strong enough to be felt by a hand placed on the outside.

Braxton Hicks contractions may be starting. These are practice contractions — irregular, not painful, usually brief. They feel like a tightening across the abdomen that fades after a minute or two. They are not labor. They are your uterus rehearsing. If contractions become regular, painful, or more frequent than four in an hour, contact your provider.

Back pain is increasingly common. Your center of gravity has shifted, your uterus is pressing on surrounding structures, and the hormone relaxin has loosened your joints. Prenatal yoga, swimming, and pelvic floor work all help significantly.

Sleep is getting harder. Finding a comfortable position becomes a real project at this stage. A pregnancy pillow — specifically one that supports both your bump and your back simultaneously — makes a genuine difference. Sleeping on your left side is generally recommended because it optimizes blood flow to the placenta.

Shortness of breath. Your uterus is now pushing upward on your diaphragm, reducing lung capacity. This is normal and will ease slightly in the final weeks when the baby drops lower into the pelvis. For now, slow down when you need to and do not push through breathlessness during exercise.

Fetal movement and kick counts

At 27 weeks your provider may begin discussing kick counts — a simple practice of monitoring your baby’s movement to ensure everything is normal. The standard guidance is to choose a consistent time of day, ideally after a meal when your baby is typically more active, and count how long it takes to feel ten distinct movements.

Ten movements in two hours is generally considered reassuring. Most babies reach that count much faster.

If you notice a significant decrease in movement that does not resolve after drinking something cold and lying on your side for an hour, contact your provider. Do not wait until the next scheduled appointment. Changes in fetal movement are one of the most important signals your baby can give you, and providers want to hear about them promptly.

Your prenatal appointments around week 27

Week 27 typically falls at or near the glucose challenge test — a screening for gestational diabetes. You drink a glucose solution and have blood drawn an hour later. No fasting required for the initial screening. If your result comes back elevated, you will be referred for a three-hour glucose tolerance test, which is the diagnostic test.

Gestational diabetes is manageable and common — affecting around 6 to 9 percent of pregnancies. It does not mean your pregnancy is high-risk by default, but it does require monitoring and usually dietary adjustments.

Your provider will also likely measure your fundal height — the distance from your pubic bone to the top of your uterus — to confirm your baby’s growth is tracking appropriately. At 27 weeks, fundal height typically measures around 27 centimeters, give or take two centimeters in either direction.

Week 27 is one of those moments in pregnancy where the abstract becomes undeniably concrete. Your baby is blinking, dreaming, hiccupping, and hearing your voice. The brain is wiring itself. The lungs are practicing. Everything that is happening is purposeful and it is happening fast.

Understanding these milestones is one piece of the larger picture of what a healthy, informed pregnancy at 27 looks like from start to finish. If you have not yet read through the complete guide to being pregnant at 27, this is a good moment to do that — it connects everything from nutrition to mental health to physical fitness in a way that week-by-week content alone cannot.

When you are ready to think practically about what comes next in terms of medical care — which appointments to book, which tests to expect, and how to stay on top of your prenatal schedule through the third trimester — prenatal appointments at 27: what tests you need and when to schedule them walks you through exactly that. Knowing what is coming medically makes the final trimester feel a lot more manageable.