Pregnancy week 39
Having grown almost 1/2 a size since the previous week, the baby in pregnancy week 39 is about 7 1/2 pounds and around 21 1/2 inches long. During week 39, fetal monitoring can come in quite handy in helping determine weather there is any sign of fetal distress during labor. When the uterus contracts, the amount of oxygen rich blood that reaches the placenta dramatically reduces. Although this is a natural and usually unproblematic event, complications can arise. There are two types of fetal monitors; internal and external. The internal monitor calls for a slip of electrode to be implanted into the baby’s skull while it is still in the womb, and would require that the mother’s water breaks before any signs of distress can be examined. The external monitor fits like a fanny pack over the mothers abdomen and works like a type of ultrasounds. At this point, most of the vernix covering the baby’s skin has dispersed and there is not much lanugo left. The baby will soon pass it’s first meconium, or bowel movement, after birth.
When the baby isn’t progressing through the birth canal by the time labor has been induced, the doctor may introduce forceps. Forceps are a tool that look like tongs and are used to clasp the baby’s head inside the vagina and help pull it out. Risks are minimal when the procedure is done carefully and expertly but do include bruising, inflammation, and more seriously, internal bleeding in the skull. Sometimes an episiotomy is used and the vaginal area may be numbed. If the uterus is not contracting well enough to push the baby out, and forceps are not an option, the doctor may use what is called a vacuum extractor. This lightly sucks the baby’s head towards the end of the birth canal. The bones in the baby’s skull are fully developed, however, they have some pieces missing to allow the head to compress in order to fit through the birth canal. The bones may slide over each other and overlap during delivery.
Current guidance (today's medical sources): At thirty-nine weeks the pregnancy is full term and the baby is ready for birth. Labour could begin any day. The brain and lungs continue to mature right up to and after birth. Staying aware of the signs of labour and of the baby's movements remains important, and any concerns are worth a call to the maternity unit.
If the baby's movements slow or change, or if your waters break, contact your maternity unit. Contact your healthcare provider promptly about heavy vaginal bleeding, severe or persistent abdominal pain, a high fever, severe or sudden headache, vision changes, or fainting. Seek urgent care if you are worried — these can be signs that need medical attention.
Sources: NHS — 39 weeks pregnant; ACOG — How to Tell When Labor Begins; Mayo Clinic — Fetal development: The 3rd trimester. Informational only. See our sources & medical-review policy.
Frequently asked questions
How many months is 39 weeks pregnant?
Week 39 falls in the third trimester. Pregnancy is usually counted in weeks (about 40 in total) rather than months, because weeks are more precise.
What is happening to the baby at 39 weeks?
At 39 weeks the pregnancy is 'full term'; the baby is ready for birth.
What symptoms are common at week 39?
Labour could start any day; staying alert to its signs is useful. Symptoms vary a lot from person to person; discuss anything that worries you with your healthcare provider.
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See the week-by-week guide →Informational only — not medical advice. Pregnancy Week to Week is a general educational reference. It is not a substitute for professional medical care, diagnosis, or treatment. Every pregnancy is different: always consult your doctor, midwife, or other qualified healthcare provider about your own pregnancy, and never disregard or delay professional advice because of something you read here. In an emergency, contact your maternity unit or local emergency number immediately.