GUIDE
This is the ideal delivery week according to ACOG — your baby is fully developed.
At 39 weeks your baby is the size of a watermelon, weighing about 7 to 7.5 pounds. All organ systems are mature, the immune system is receiving its final antibodies from you, and your baby is fully ready for life outside the womb. Labor could begin at any moment.
Be prepared from day one
Your baby is now the size of a watermelon — roughly 20 inches long and weighing between 7 and 7.5 pounds. This is the week ACOG considers the beginning of the ideal delivery window. Your baby is fully developed and ready to meet you.
All organ systems are mature and functional. The lungs are producing plenty of surfactant and are ready for that first breath. The heart is pumping about 28 quarts of blood per day. The digestive system is ready to process breast milk or formula. The kidneys are filtering waste effectively. Every system is go.
The immune system is receiving its final dose of antibodies from you through the placenta. These IgG antibodies will provide passive immunity for the first several months of your baby's life, protecting against infections while their own immune system develops and begins responding to vaccines. This transfer of immunity is one of the most remarkable aspects of pregnancy.
The brain at 39 weeks is significantly more mature than it was even at 37 weeks. Neural pathways are more myelinated (coated in the fatty sheath that speeds signal transmission), and brain volume has increased substantially. This is the primary reason ACOG shifted its recommendation against elective delivery before 39 weeks — those final two weeks of brain development matter.
Your baby has shed most of the vernix and lanugo. Their skin is smooth, their fat stores are ample, and their appearance is essentially what you'll see at birth. They're practicing breathing, sucking, and swallowing. They may be head-down and deeply engaged in your pelvis, or they may still have some room to move.
At 39 weeks, waiting is the hardest part. Your body may feel like it's been pregnant forever, and every sensation is analyzed: was that a contraction? Is something happening? The hypervigilance is exhausting, and it's completely normal.
Your cervix may be starting to dilate (open) and efface (thin). Your provider may check this at appointments, but it's worth knowing that cervical status is not a reliable predictor of when labor will start. You can be 3 cm dilated for weeks, or you can go from 0 to active labor in hours. Try not to read too much into the numbers.
Signs that labor may be approaching include: loss of the mucus plug, bloody show, persistent lower back pain, diarrhea, a sudden burst of energy (nesting), and Braxton Hicks that seem to be getting more regular. None of these mean labor is about to start right now, but they suggest your body is preparing.
Real labor is unmistakable once it's established. Contractions will be regular, progressive, and impossible to talk through. They won't stop when you rest, drink water, or change positions. When this happens, start timing them and review our guide on when to go to the hospital or follow your provider's guidance.
Understanding the stages of labor can help you manage expectations. Early labor can last hours (or even days for some first-time parents). Active labor is when things progress quickly. Transition is intense but brief. And then — pushing and meeting your baby.
If your provider has discussed the possibility of a C-section, whether planned or as a contingency, being informed about the procedure will help you feel prepared. You may also want to explore natural pain relief options for labor so you know all your choices when the time comes.
Emotionally, this is often a time of intense anticipation mixed with moments of fear. That's normal. You are more prepared than you think. Trust your body, trust your care team, and trust yourself.
Every pregnancy is different. You may experience all, some, or none of these symptoms.
One week to your due date. Everything is ready. Now it's about patience, rest, and being alert.
With weekly appointments, your provider is monitoring you closely. Share any new symptoms, ask about your cervical status if you're curious, and discuss your options if labor hasn't started by your due date. If your provider recommends induction, ask about the reasoning, timing, and what to expect.
Review the guidelines with your provider. The general 5-1-1 rule (contractions 5 minutes apart, lasting 1 minute, for 1 hour) is a starting point. Go immediately if your water breaks, you have heavy bleeding, you feel decreased fetal movement, or you have a severe headache with vision changes. When in doubt, call — no one will judge you for a false alarm.
This may be the hardest advice you'll hear: be patient. The waiting at 39 weeks can feel unbearable, especially if you're uncomfortable. Well-meaning people asking 'Any signs yet?' doesn't help. Try to focus on things that bring you comfort and distraction. Your baby will come when they're ready.
Labor is a marathon, not a sprint. If you can sleep, sleep. If you can nap, nap. If you can sit instead of stand, sit. Your body is about to do extraordinary work, and going into labor rested gives you the best chance of the birth experience you're hoping for. This is not the time for ambitious projects.
When in doubt, call your provider. It's always better to check and be reassured than to wait and worry.
Next week is week 40 — your due date week. Only about 5% of babies arrive on their actual due date, so don't be surprised if your baby hasn't arrived yet. Your provider will continue monitoring you closely.
Looking back, week 38 was when full term began and all organ systems became ready. If you haven't reviewed signs of labor recently, one more read-through can boost your confidence.
It's also not too early to start thinking about postpartum recovery — knowing what to expect after delivery helps you plan support and feel less overwhelmed.
You're at the finish line. Every hour brings you closer to holding your baby. It's almost time.
This guide is for informational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider with any questions about your pregnancy.
