Fetal Growth Chart Week by Week: Baby Growth & Development

From a tiny cluster of cells to a fully developed newborn, pregnancy is a journey of exciting changes each week as your unborn baby grows. With accurate, trustworthy information, you can find peace of mind on this amazing journey and prepare for each stage of pregnancy with confidence. When your baby hits new developmental milestones, big changes will happen in your body.

A week-by-week Fetal Growth Chart can give you a clear picture of your baby's development and important developmental milestones, from the first heartbeat to the last few weeks before delivery. Knowing what to expect week by week helps you avoid confusion, develop realistic expectations and prepare yourself for labour, delivery and the sensitive postpartum period. 

How Does a Fetal Growth Chart Help Track Your Baby's Weekly Progress?

A Fetal Growth Chart is a clinical reference chart used by obstetricians to monitor fetal dimensions, skeletal development, and overall weight gain during routine prenatal checkups. The ultrasound measurements are then compared to known population percentiles. This allows doctors to see if the fetus is growing steadily and within normal ranges.

In the first trimester, doctors measure Crown-Rump Length (CRL). This is the distance between the top of the embryonic head and the outer curve of the bottom. After the first trimester, ultrasound assessments rely on measurements such as head circumference, abdominal circumference, femur length, and biparietal diameter to estimate your baby's size, weight, and overall growth. Together, these measurements provide a clear picture of your baby's development throughout pregnancy. For more information about routine scans, see this guide to prenatal tests and scans.

Note: Growth percentiles are statistical distribution markers rather than absolute health scores. 

If a fetus is at the 20th or 80th percentile, they are developing perfectly normally, as long as their individual growth curve remains stable at subsequent appointments.

What are the Key Fetal Milestones Across Each Trimester?

Early cellular differentiation, structural expansion, and rapid tissue maturation are the three separate physiological stages of fetal growth. Certain anatomical milestones necessary for survival outside the womb are established during each trimester. You can also explore this pregnancy trimester guide for an overview of changes during each stage. 

First Trimester (Weeks 1 to 12)

During these initial weeks, organogenesis happens quickly. The neural tube unites to form the foundation of the central nervous system by week four. By week 6, primitive heart contractions start, limb buds appear by week 8, and by week 12, all major organ structures, toes, and fingers are fully formed.

Second Trimester (Weeks 13 to 27)

During this phase, musculoskeletal expansion greatly quickens. Maternal perception of fetal movement usually starts around week 20, and facial muscles permit reflex movements around week 16. Vernix caseosa, a lipid layer that protects sensitive skin from extended exposure to amniotic fluid, is first produced by specialised dermal glands at week 24.

Third Trimester (Weeks 28 to 40)

Subcutaneous fat storage, pulmonary surfactant production, and neurological development are given priority in the last stage. Ossification is finished while the bones are still pliable enough to be delivered. In order to help with postnatal thermoregulation, the foetus rapidly gains weight between weeks 36 and 40 and sheds the majority of its vernix and lanugo hair.

How Can You Get Ready for Your Baby's Arrival During the Final Weeks of Pregnancy?

There is a point in pregnancy when the focus shifts subtly. You’re not tracking weekly milestones; you’re folding tiny clothes, checking your hospital bag and wondering if you’ve got everything. It’s totally normal, because doing a little bit of prep now can make those first few days with your newborn feel a lot less rushed.

Start by gathering the essentials, including diapers, baby clothes, feeding supplies, toiletries, a safe sleeping space, and any important hospital documents. If you’re ticking off a list item by item, you’re already doing enough. The goal is not to have a perfect nursery. It is to create a space where you can feel confident in your baby.

Conclusion

While a fetal growth chart can provide important clinical clarity during pregnancy, it’s essential to give equal importance to home preparation for postnatal skin health. Choosing the right newborn supplies will help to keep your baby healthy and comfortable after birth.

Traditional plastic-backed nappies trap humidity on the infant skin. This increases localised skin temperature and compromises the epidermal barrier. Breathable, high-performance diapers help prevent fluid accumulation and friction-irritation.

The advanced ventilation engineering of MamyPoko Pants Skin Breathe Care diapers ensures dependable dermatological protection. These nappies are made with a specialised Half Skin Touch Airy Sheet that reduces 50% direct material-to-skin contact, allowing continuous airflow across your baby’s bottom. 3X breathable fabric quickly releases excess heat and humidity to keep newborn skin thoroughly dry, comfortable and protected from diaper rash.