IVF Pregnancy Week by Week
Your IVF pregnancy follows the same developmental stages as a natural pregnancy, but knowing your exact conception date gives you a more precise timeline. This week-by-week guide takes you from embryo transfer through your due date, covering what's happening with your baby and what to expect at each stage.
Pregnancy at a Glance: Trimester Overview
Understanding Your IVF Pregnancy Timeline
After a successful embryo transfer, pregnancy is measured in gestational weeks starting from a theoretical "last menstrual period" (LMP). For IVF patients, this dating is more accurate than natural conception because we know the exact day of fertilization and transfer.
For a day 5 blastocyst transfer, you're already 2 weeks and 5 days pregnant at the time of transfer. This guide starts from that point and follows your pregnancy through all 40 weeks.
The most critical period for organ formation. By week 13, all major organs are formed and the risk of miscarriage drops to about 2-3%. Your baby grows from a tiny cluster of cells to 74mm (size of a lemon).
The Two-Week Wait (Weeks 2-4)
Week 2-3: Transfer and Implantation
What's happening: If you had a day 5 transfer, you start at 2 weeks and 5 days. The blastocyst hatches from its protective shell (zona pellucida) and begins attaching to your uterine lining. This implantation process takes several days to complete.
What you may feel: Many women feel nothing different. Some report light spotting (implantation bleeding), mild cramping, or breast tenderness. However, these can also be progesterone side effects, so they're not reliable pregnancy indicators.
Medical care: Continue all medications exactly as prescribed. Avoid strenuous exercise and intercourse if your clinic recommends it.
Week 4: Beta hCG Testing
What's happening: The implanted embryo is producing hCG (human chorionic gonadotropin). By the end of week 4 (approximately 9-12 days post-transfer for a day 5 embryo), hCG levels are usually high enough to detect.
What you may feel: Early pregnancy symptoms may begin: fatigue, breast tenderness, frequent urination. Many women still feel normal at this stage.
Medical care: Your first beta hCG blood test typically occurs 9-14 days post-transfer. A positive result is exciting, but your clinic will likely repeat the test in 2-3 days to confirm hCG levels are rising appropriately (doubling every 48-72 hours).
First Trimester: Weeks 5-13
Week 5: Early Development
Baby's development: Your baby is now called an embryo. The neural tube (which becomes the brain and spinal cord) begins forming. The heart starts as a simple tube and begins beating, though it's not yet detectable on ultrasound. The embryo is about 2mm long—the size of a sesame seed.
What you may feel: Morning sickness may begin. Breast tenderness, fatigue, and mood changes are common. Some women experience heightened sense of smell.
Week 6: First Ultrasound Window
Baby's development: The heart is beating at 100-160 beats per minute and may be visible on ultrasound. Arm and leg buds are forming. The embryo is about 4-6mm (size of a sweet pea).
What you may feel: Nausea may intensify. Fatigue often peaks in the first trimester. You may notice bloating even though your belly isn't showing yet.
Medical care: Many IVF clinics schedule the first ultrasound around 6-7 weeks. This confirms the pregnancy is in the uterus (not ectopic) and usually detects a heartbeat.
Week 7: Heartbeat Confirmation
Baby's development: The embryo has doubled in size since last week (now about 10mm). Facial features begin forming—eyes, ears, nose, and mouth are starting to develop. Brain development is rapid.
What you may feel: Morning sickness may be at its worst. Frequent urination becomes more noticeable. You may feel more emotional than usual.
Medical care: Viability ultrasound confirms a strong heartbeat. Once a heartbeat is confirmed at 7+ weeks, the miscarriage risk drops significantly.
Week 8: Major Organ Development
Baby's development: All major organs have begun forming. Fingers and toes are webbed but present. The embryo is making small movements, though you can't feel them yet. Size: about 16mm (size of a raspberry).
What you may feel: Symptoms continue. Some women notice food aversions or cravings beginning. Your sense of smell may be very sensitive.
Medical care: Many IVF patients "graduate" from their fertility clinic around this time and transfer care to a regular OB-GYN. NIPT (non-invasive prenatal testing) can be performed starting around this time.
Week 9: Embryo to Fetus
Baby's development: Your baby officially becomes a fetus. External genitalia begin forming (though not yet visible on ultrasound). The tail disappears. Size: about 23mm (size of a grape).
What you may feel: Your uterus is expanding, which may cause occasional cramping or pulling sensations. Fatigue and nausea typically continue.
Week 10: Human Features
Baby's development: Your baby now looks distinctly human. Vital organs are functional. Bones are beginning to harden. The baby can make small movements and even hiccup. Size: about 31mm (size of a kumquat).
What you may feel: You may notice your waistline thickening, though you probably don't look pregnant yet. Visible veins may appear on your breasts and abdomen due to increased blood volume.
Week 11: Rapid Growth
Baby's development: The baby's head is still large compared to the body but proportions are changing. Tooth buds form under the gums. Hair follicles develop. Size: about 41mm (size of a fig).
What you may feel: For some women, nausea begins to improve. Your energy may start returning. The risk of miscarriage continues to decrease.
Medical care: NT scan (nuchal translucency screening) is typically performed between 11-14 weeks to screen for chromosomal abnormalities.
Week 12: End of Highest Risk Period
Baby's development: Reflexes are developing—the baby can open and close fingers, curl toes, and make sucking movements. Intestines, which developed in the umbilical cord, move into the abdomen. Size: about 54mm (size of a lime).
What you may feel: Many women start feeling better as hormone levels stabilize. You may begin showing, especially if this isn't your first pregnancy.
Medical care: Many couples choose to announce their pregnancy after 12 weeks, as the miscarriage risk has dropped significantly (to about 2-3%).
Week 13: End of First Trimester
Baby's development: Fingerprints are forming. Vocal cords are developing. The baby's body is growing faster than the head now. Size: about 74mm (size of a lemon).
What you may feel: The first trimester fatigue and nausea typically improve significantly. Your appetite may return. Many women feel their best during the second trimester.
Often called the "honeymoon phase." Morning sickness fades, energy returns, and you begin feeling baby movements. The anatomy scan at 18-22 weeks checks all major organs. By week 24, your baby reaches the viability milestone.
Second Trimester: Weeks 14-27
Week 14: The "Honeymoon" Phase Begins
Baby's development: The baby can make facial expressions—squinting, frowning, grimacing. Kidney function begins (baby produces urine). Fine hair (lanugo) starts covering the body. Size: about 87mm.
What you may feel: Energy often increases dramatically. Morning sickness usually resolves. Your belly is likely visibly growing now.
Weeks 15-17: Movement Begins
Baby's development: The skeleton is hardening from cartilage to bone. The baby is actively moving, though you may not feel it yet. If you're having a girl, eggs are forming in her ovaries. By week 17, the baby is about 130mm (size of a pear).
What you may feel: First-time mothers may begin feeling "quickening" (first fetal movements) around week 16-20. It often feels like bubbles, flutters, or gas.
Weeks 18-20: Anatomy Scan
Baby's development: The baby is developing sleep-wake cycles. Ears are functional—the baby can hear your voice and heartbeat. Vernix (a waxy coating) forms on the skin. At week 20, the baby is about 160mm—you're halfway there!
What you may feel: Fetal movements become more noticeable and regular. You may experience round ligament pain as your uterus grows.
Medical care: The anatomy scan (detailed ultrasound) is typically performed at 18-22 weeks. This comprehensive exam checks all major organs, measures growth, and can reveal the baby's sex if you want to know.
Weeks 21-24: Viability Milestone
Baby's development: Rapid brain development continues. The baby is practicing breathing movements (inhaling amniotic fluid). Fingerprints and footprints are complete. By week 24, the baby weighs about 600g (1.3 lbs).
Week 24 is the viability milestone: Babies born at 24 weeks have a chance of survival with intensive medical care, though outcomes improve significantly with each additional week in the womb.
What you may feel: Your belly is clearly pregnant now. You may experience Braxton Hicks contractions (practice contractions). Back pain may begin as your center of gravity shifts.
Medical care: Glucose screening test for gestational diabetes is typically performed between 24-28 weeks.
Weeks 25-27: End of Second Trimester
Baby's development: Eyes open for the first time. The baby responds to light and sound. Lungs are developing but not yet mature enough for breathing air. Brain activity increases—sleep includes REM phases. By week 27, the baby weighs about 900g (2 lbs).
What you may feel: You may notice the baby responding to loud sounds or bright lights. Heartburn and shortness of breath may increase as your uterus pushes against your diaphragm.
The final stretch. Your baby gains most of its weight during this trimester, going from about 1 kg (2.2 lbs) at week 28 to approximately 3.4 kg (7.5 lbs) at birth. Lungs mature, fat deposits build, and the baby prepares for life outside the womb.
Third Trimester: Weeks 28-40
Week 28: Third Trimester Begins
Baby's development: The baby can blink, cough, hiccup, and has more developed sucking ability. Brain development continues rapidly. Fat deposits begin, making the baby look less wrinkled. Weight: about 1kg (2.2 lbs).
What you may feel: Discomfort increases as the baby grows. Leg cramps, back pain, and difficulty sleeping are common. Kick counts become important—you should feel regular movement.
Medical care: Appointments may become more frequent (every 2-3 weeks). RhoGAM injection is given around this time if you're Rh-negative.
Weeks 29-32: Rapid Weight Gain
Baby's development: The baby is gaining about 250g (half a pound) per week. Bones are fully developed but still soft. The baby may settle into a head-down position. By week 32, the baby weighs about 1.8kg (4 lbs).
What you may feel: Shortness of breath and heartburn may worsen. You may feel the baby's movements as distinct kicks, punches, and rolls. Braxton Hicks contractions may become more noticeable.
Weeks 33-36: Final Development
Baby's development: Lungs are nearly mature. The baby is running out of room and movements may feel different—more squirming than kicking. Fat continues accumulating. By week 36, the baby weighs about 2.6kg (5.8 lbs).
What you may feel: "Lightening" may occur—the baby drops lower into your pelvis, making breathing easier but increasing pressure on your bladder. Pelvic discomfort may increase.
Medical care: Appointments are typically weekly from week 36. Group B strep test is performed around week 35-37. Your provider may check cervical changes.
Week 37: Full Term
Baby's development: Your baby is now considered full term. All major systems are mature. The baby continues gaining weight and practicing breathing. Weight: about 2.9kg (6.3 lbs).
What you may feel: You may experience increased Braxton Hicks contractions, nesting urges, loose stools, or loss of mucus plug—all potential signs labor is approaching.
Weeks 38-39: Ready for Birth
Baby's development: The baby sheds most of the lanugo (fine body hair) and vernix (waxy coating). Brain and lungs continue maturing. Average weight at 39 weeks: about 3.3kg (7.3 lbs).
What you may feel: Many women feel very ready to not be pregnant anymore. Discomfort peaks. You may experience "false labor" (contractions that don't progress).
Week 40: Your Due Date
Baby's development: Your baby is fully developed and ready for life outside the womb. Average weight: about 3.4kg (7.5 lbs), length about 51cm (20 inches).
What happens: Only about 5% of babies are born on their exact due date. If labor doesn't begin naturally, your provider will discuss options, which may include continued monitoring or induction.
Weeks 41-42: Post-Due Date
If you haven't delivered by your due date, your provider will monitor you more closely. Most providers recommend induction by 41-42 weeks to avoid risks associated with prolonged pregnancy.
Complete Week-by-Week Development Table
The following table provides a comprehensive reference for all 40 weeks of pregnancy, showing approximate baby size, weight, and the key development happening each week:
| Week | Size (length) | Weight | Key Development |
|---|---|---|---|
| 4 | ~1 mm | <1 g | Implantation complete; hCG detectable |
| 5 | ~2 mm | <1 g | Neural tube forming; heart begins beating |
| 6 | ~5 mm | <1 g | Heartbeat visible on ultrasound; arm/leg buds |
| 7 | ~10 mm | <1 g | Facial features start; brain developing rapidly |
| 8 | ~16 mm | ~1 g | All major organs forming; fingers/toes webbed |
| 9 | ~23 mm | ~2 g | Embryo becomes fetus; external genitalia forming |
| 10 | ~31 mm | ~4 g | Bones hardening; vital organs functional |
| 11 | ~41 mm | ~7 g | Tooth buds form; hair follicles develop |
| 12 | ~54 mm | ~14 g | Reflexes developing; intestines move to abdomen |
| 13 | ~74 mm | ~23 g | Fingerprints forming; vocal cords developing |
| 14 | ~87 mm | ~43 g | Facial expressions; lanugo (fine hair) appears |
| 16 | ~12 cm | ~100 g | Skeleton hardening; movement increasing |
| 18 | ~14 cm | ~190 g | Ears functional; sleep-wake cycles begin |
| 20 | ~16 cm | ~300 g | Halfway point; anatomy scan; vernix forming |
| 22 | ~19 cm | ~430 g | Rapid brain development; fingerprints complete |
| 24 | ~21 cm | ~600 g | Viability milestone; lungs developing surfactant |
| 26 | ~23 cm | ~760 g | Eyes open; responds to light and sound |
| 28 | ~25 cm | ~1.0 kg | Third trimester; fat deposits begin; can blink |
| 30 | ~27 cm | ~1.3 kg | Brain growing rapidly; bone marrow producing blood |
| 32 | ~28 cm | ~1.8 kg | Bones fully developed (still soft); may be head-down |
| 34 | ~30 cm | ~2.1 kg | Lungs nearly mature; central nervous system maturing |
| 36 | ~34 cm | ~2.6 kg | Fat accumulating; "lightening" may occur |
| 37 | ~36 cm | ~2.9 kg | Full term; all major systems mature |
| 38 | ~35 cm | ~3.1 kg | Lanugo shedding; brain and lungs continue maturing |
| 39 | ~36 cm | ~3.3 kg | Ready for birth; continuing to add fat |
| 40 | ~36 cm | ~3.4 kg | Due date; fully developed for life outside womb |
Note: Sizes represent crown-to-rump length through week 20, and crown-to-heel estimates thereafter. All measurements are averages and individual variation is normal.
Baby Weight Gain by Month
Most weight gain happens in the third trimester. Here is the approximate average baby weight at the end of each month:
Tracking Your IVF Pregnancy Week by Week
Use our IVF Due Date Calculator to determine your current gestational age and see all your upcoming milestones. The calculator shows:
- Your exact week and day
- Which trimester you're in
- Key upcoming appointments and milestones
- Days until your due date
- A visual progress bar
Our Timeline tab provides a visual week-by-week overview of your entire pregnancy at a glance.
Key Takeaways
Your IVF pregnancy progresses through the same stages as any pregnancy. What makes it special is the precision of dating and the knowledge that your baby was wanted, planned for, and started their journey with the help of science and dedicated medical care.
Remember that every pregnancy is unique. Use this guide as a general reference, but always discuss concerns or symptoms with your healthcare provider.
This week-by-week guide is for informational purposes only. Every pregnancy is different. Always consult your healthcare provider for personalized guidance and report any concerning symptoms promptly.