Your Week-by-Week Guide to Amazing Foetal Development
Discover the incredible journey of pregnancy with this week-by-week guide to foetal development. Learn key milestones, symptoms, and self-care tips for every stage.
Written by Dr. Siri Nallapu
Reviewed by Dr. D Bhanu Prakash MBBS, AFIH, Advanced certificate in critical care medicine, Fellowship in critical care medicine
Last updated on 23rd Sep, 2025
Introduction
The journey of pregnancy is a remarkable 40-week adventure, a period of incredible transformation where a single cell evolves into a fully formed baby. Understanding foetal development week by week can be a source of wonder, reassurance, and connection for expectant parents. This guide demystifies that process, offering a window into the womb to show you exactly what’s happening and when. From the miraculous first flicker of a heartbeat to the final preparations for life outside the womb, we’ll walk you through each key milestone. We’ll also connect these changes to what you might be experiencing in your own body, providing a holistic view of this extraordinary time. Whether you're in your first trimester or eagerly awaiting your due date, this comprehensive breakdown will be your trusted companion.
First Trimester; Weeks 5-8 (Embryonic Period)
The embryonic period is arguably the most critical phase of entire pregnancy development. While you might have just discovered you're pregnant, incredible things are happening.
Major Milestones: The Neural Tube and Heartbeat
Around week 5, the neural tube begins to form. This structure will become your baby's brain, spinal cord, and backbone—making adequate folic acid intake crucial to support its healthy closure. By week 6, a momentous event occurs: the baby’s heart begins to beat. Initially, it's a simple tube that will loop and fold into the four chambers we know, but it may already be detectable on a vaginal ultrasound. Tiny buds that will become arms and legs also emerge. By week 8, the embryo graduates from webbed hands and feet to distinct fingers and toes. All essential organs have begun to form, laying the foundation for everything to come.
Early Pregnancy Symptoms and Self-Care
This rapid internal development is often mirrored by significant symptoms for the mother. Rising hormones like hCG and progesterone can lead to fatigue, tender breasts, and the infamous morning sickness (which can strike at any time of day). This is your body’s way of supporting the pregnancy. Self-care is vital: prioritise rest, eat small, frequent meals to manage nausea, and stay hydrated. If your nausea is severe and preventing you from keeping any food or liquids down, it’s important to consult a doctor online with Apollo24|7 to rule out hyperemesis gravidarum and get advice on management.
Second Trimester; Weeks 17-20 (Halfway There!)
Often called the "honeymoon period" of pregnancy, the second trimester brings welcome relief for many and some of the most exciting pregnancy milestones.
Feeling Your Baby Move (Quickening)
Sometime between weeks 18 and 22 (sooner for second-time parents), you'll experience one of pregnancy's most magical sensations: quickening. These first movements are often described as flutters, bubbles, or gentle popcorn popping. As the weeks progress, these will become unmistakable kicks, rolls, and jabs. Keeping a rough mental note of movement patterns is a good practice, though a consistent daily pattern often doesn't emerge until closer to 28 weeks.
The Anatomy Scan: Finding Out the Sex
Typically performed between weeks 18 and 22, the anatomy scan is a detailed ultrasound that checks your baby’s physical development. The sonographer will measure the head, abdomen, and femur, examine the brain, heart, spine, kidneys, and other organs for normal growth. This is also the scan where, if you choose to and if the baby is in a favourable position, you can often find out the biological sex. It’s a profound opportunity to see your baby in detail and can provide significant peace of mind.
Third Trimester; Weeks 31-35 (Final Lung Maturation)
The home stretch! Your baby is now primarily gaining weight and putting the finishing touches on crucial systems before birth.Consult a Gynaecologist for the best advic
Positioning for Birth: Head Down or Breech?
By now, most babies will have assumed their birth position: head-down (cephalic presentation). This is the ideal position for a vaginal delivery. However, some babies may be bottom-first (breech) or sideways (transverse lie). Your healthcare provider will check the baby's position at your appointments. If your baby is breech as you approach your due date, your doctor can discuss options like External Cephalic Version (ECV) to try and turn the baby manually.
Dealing with Shortness of Breath and Insomnia
As your uterus expands, it pushes up against your diaphragm, making it harder to take deep breaths. This is completely normal. You might find relief by maintaining good posture and sleeping propped up with pillows. Pregnancy insomnia is also common due to discomfort, anxiety, and frequent trips to the bathroom. Establishing a calming bedtime routine, using pillows for support, and practising relaxation techniques can help. If your sleep issues are severely impacting your daily life, it’s worth discussing it with your doctor during a prenatal check-up.
Conclusion
Witnessing the stages of foetal development is a profound reminder of the miracle of life. From a cluster of cells to a kicking, hiccupping, responsive baby, each week brings a new milestone. This week-by-week guide aims to empower you with knowledge, helping you understand the incredible processes happening within your body and forge a deeper connection with your growing baby. While this information is valuable, remember that every pregnancy is unique. Some babies measure a week ahead, others a week behind; some mothers feel movement early, others later. These variations are usually normal. Use this guide as a source of wonder, not worry. Your most important partner on this journey is your healthcare provider, who can offer personalised care and address any specific concerns you have along the way.Consult a Gynaecologist for the best advic
Consult a Gynaecologist for the best advic
Dr. Mona Yadav
Obstetrician and Gynaecologist
19 Years • MBBS, MD (Obstetrics & Gynaecology)
Dombivli
Nulife multispeciality, Dombivli
Dr. Asha Rani Singh
Obstetrician and Gynaecologist
24 Years • MBBS DGO
Delhi
Dr Asha Rani Singh Clinic, Delhi
Dr. Parul Sharma
Obstetrician and Gynaecologist
8 Years • MBBS, MS (Obstetrics & Gynaecology)
New Delhi
THE DOCTORS NESST, New Delhi
Dr. K Anusha
Obstetrician and Gynaecologist
4 Years • MBBS, DGO
Yemmiganur
SRINIVASAA HOSPITAL, Yemmiganur
Dr. Shyamala Devi
Obstetrician and Gynaecologist
38 Years • MBBS, MS Obstetrics & Gynaecology
Vijayawada
Sri Shivshakti Nilayam, Vijayawada
Consult a Gynaecologist for the best advic
Dr. Mona Yadav
Obstetrician and Gynaecologist
19 Years • MBBS, MD (Obstetrics & Gynaecology)
Dombivli
Nulife multispeciality, Dombivli
Dr. Asha Rani Singh
Obstetrician and Gynaecologist
24 Years • MBBS DGO
Delhi
Dr Asha Rani Singh Clinic, Delhi
Dr. Parul Sharma
Obstetrician and Gynaecologist
8 Years • MBBS, MS (Obstetrics & Gynaecology)
New Delhi
THE DOCTORS NESST, New Delhi
Dr. K Anusha
Obstetrician and Gynaecologist
4 Years • MBBS, DGO
Yemmiganur
SRINIVASAA HOSPITAL, Yemmiganur
Dr. Shyamala Devi
Obstetrician and Gynaecologist
38 Years • MBBS, MS Obstetrics & Gynaecology
Vijayawada
Sri Shivshakti Nilayam, Vijayawada
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Frequently Asked Questions
1. What is the difference between an embryo and a foetus?
The term 'embryo' refers to the developing baby from conception until the end of the 8th week of pregnancy. This is when all major internal and external structures begin to form. After the 8th week, and until birth, the developing baby is called a 'foetus.' This period is marked by tremendous growth and the refinement of all those initial structures.
2. When can you typically hear the baby's heartbeat?
A foetal heartbeat can first be detected by a vaginal ultrasound as early as 5.5 to 6 weeks of pregnancy. It may take longer to detect with an abdominal ultrasound. The sound may become audible with a Doppler device, which is used during prenatal check-ups, between weeks 10 and 12, though it can sometimes be later.
3. Is it normal not to feel baby move at 20 weeks?
Yes, it can be perfectly normal, especially for first-time mothers. The experience of feeling those first movements (quickening) varies widely and typically occurs between 18 and 22 weeks. If you are concerned about a lack of movement as you get further along, always contact your healthcare provider for reassurance.
4. What are the most critical weeks of foetal development?
The first trimester (weeks 1-12) is the most critical for development. This is when the baby's organs, brain, spinal cord, arms, and legs are forming. This is why early and consistent prenatal care, including taking folic acid, is so vital for preventing congenital disabilities.
5. What does a baby look like in the womb at 12 weeks?
By week 12, the baby looks unmistakably human, though in miniature. It is about the size of a lime. The head is still large compared to the body, but the eyes, ears, and nose are in their correct positions. Fingers and toes have fully separated, and nails are beginning to grow. The kidneys are starting to produce urine.