37 Weeks Pregnant: Baby Development & What to Expect

How Big Is My Baby at 37 Weeks?

At 37 weeks pregnant, your baby weighs approximately 2.9 to 3.2 kg (6.4 to 7 pounds) and measures about 48 cm (19 inches) from head to heel. Your baby is about the size of a winter melon or a bunch of Swiss chard, though there is significant variation between babies at this stage.

Your baby has been gaining weight rapidly over the past few weeks, putting on about 200 grams (half a pound) per week. This weight gain is crucial because it helps your baby build up fat stores that will regulate their body temperature after birth. The fat layer also gives your baby that adorable plump appearance and smooth skin that newborns are known for.

At 37 weeks, your baby's head circumference and abdominal circumference are approximately equal. The bones in your baby's skull remain soft and flexible to allow them to pass through the birth canal – these bones won't fully fuse until early adulthood, allowing the brain to continue growing during childhood.

Your baby's fingernails have now grown to the tips of their fingers, and some babies are even born with nails that need trimming. The lanugo (fine hair covering the body) has mostly disappeared, though some may remain on the shoulders and back. The vernix caseosa – the white, creamy substance protecting your baby's skin – may be starting to shed, though some will remain until birth.

Lung Development at 37 Weeks

Your baby's lungs are the last major organs to fully mature, and at 37 weeks they are in the final stages of development. Your baby has been practicing breathing movements for weeks by inhaling and expelling amniotic fluid. This practice helps strengthen the respiratory muscles and stimulates lung development.

The lungs are now producing adequate amounts of surfactant, the substance that prevents the tiny air sacs (alveoli) from collapsing when your baby takes their first breath. While babies born at 37 weeks generally do well, research shows that waiting until 39 weeks when possible allows for optimal lung maturation and reduces the risk of respiratory complications.

Brain Development Continues

Your baby's brain is developing rapidly, adding billions of new nerve connections every day. The brain has developed distinct regions responsible for different functions including movement, sensory processing, and primitive emotions. However, brain development continues well after birth – in fact, your baby's brain will triple in size during the first year of life.

Studies show that babies born at 39-40 weeks have better outcomes in terms of brain development compared to those born at 37-38 weeks. This is one reason why elective deliveries before 39 weeks are not recommended unless medically indicated.

What Changes Are Happening in Your Body?

At 37 weeks, many women experience their baby dropping lower into the pelvis (lightening), increased pelvic pressure, Braxton Hicks contractions, difficulty sleeping, and colostrum production. Your pelvis has expanded, and you may feel increased pressure on your bladder causing more frequent urination.

As you approach your due date, your body undergoes significant changes in preparation for labor and delivery. Understanding these changes can help you differentiate between normal pregnancy symptoms and signs that require medical attention.

Lightening: When Baby Drops

Around week 37, many babies settle deeper into the pelvis in preparation for birth. This process, called "lightening" or "engagement," occurs when your baby's head descends into the pelvic cavity. For first-time mothers, this often happens two to four weeks before delivery, while women who have given birth before may not experience it until labor begins.

When lightening occurs, you may notice that you can breathe more easily as pressure on your diaphragm decreases. However, this comes with a trade-off: increased pressure on your bladder leads to more frequent trips to the bathroom, and you may feel increased pressure in your pelvis and perineum. Some women describe this sensation as feeling like the baby might "fall out."

Your healthcare provider can check whether your baby's head is engaged during your prenatal appointment by palpating your abdomen. When they say the head is "fixed," it means the baby has dropped so far into the pelvis that the head cannot be easily moved or dislodged.

Braxton Hicks Contractions

Braxton Hicks contractions, also known as "practice contractions," often become more frequent and noticeable in the final weeks of pregnancy. These contractions cause your uterus to tighten and relax, helping to prepare your body for labor. Unlike true labor contractions, Braxton Hicks are typically irregular, don't increase in intensity over time, and often go away with rest or a change in position.

You may notice that Braxton Hicks contractions are more common after physical activity, when you're dehydrated, or after sexual activity. While they can be uncomfortable, they are a normal part of late pregnancy and serve an important purpose in preparing your uterus for the work of labor.

Colostrum Production

By week 37, your breasts have been preparing for breastfeeding for months, and many women notice that their breasts have begun producing colostrum. Colostrum is the thick, yellowish "first milk" that is incredibly rich in antibodies, proteins, and nutrients. It provides everything your newborn needs in the first few days of life before your mature milk comes in.

Some women leak colostrum during pregnancy, while others don't – both are completely normal. Whether or not you leak colostrum has no bearing on your ability to breastfeed. If you do experience leaking, breast pads can help absorb the moisture.

Sleep Difficulties

Sleep becomes increasingly challenging in the final weeks of pregnancy. Your growing belly makes finding a comfortable position difficult, and you may be awakened frequently by the need to urinate, Braxton Hicks contractions, leg cramps, or simply the inability to get comfortable.

Many women find that sleeping on their side with a pillow between their knees and another supporting their belly provides the most comfort. While occasional nights of poor sleep are normal, if you're experiencing persistent insomnia or excessive daytime fatigue, discuss this with your healthcare provider.

What Happens at Your Week 37 Prenatal Visit?

At your 37-week prenatal visit, your healthcare provider will check your baby's position, listen to the fetal heartbeat, measure fundal height, check your blood pressure and urine, and may perform a Group B Strep test. They will also assess whether your baby's head is engaged in the pelvis.

Prenatal visits typically occur weekly during the final month of pregnancy, allowing your healthcare provider to closely monitor both your health and your baby's well-being as you approach your due date.

During your week 37 appointment, your provider will perform several routine assessments. They will listen to your baby's heartbeat using a Doppler device or fetoscope, typically finding it in the range of 110-160 beats per minute. They will measure your fundal height – the distance from your pubic bone to the top of your uterus – which should be approximately 35-37 centimeters at this stage.

Your healthcare provider will also palpate your abdomen to determine your baby's position and check whether the head is engaged in the pelvis. This examination, often called "Leopold's maneuvers," helps identify whether your baby is head-down (vertex), breech, or transverse. Knowing your baby's position is important for planning your delivery.

Group B Streptococcus Screening

If you haven't already been tested, your healthcare provider may perform a Group B Streptococcus (GBS) screening between weeks 36 and 37. GBS is a common bacterium that can live in the vagina or rectum without causing symptoms in adults but can potentially be passed to the baby during birth.

The test involves taking a simple swab from the vagina and rectum. If you test positive for GBS, you will receive intravenous antibiotics during labor to protect your baby from infection. GBS positivity does not affect how you give birth or require early delivery – it simply means you'll receive antibiotics during labor.

What If My Baby Is Breech at 37 Weeks?

Breech presentation means your baby is positioned bottom-down instead of head-down. At 37 weeks, your healthcare provider may offer an external cephalic version (ECV) to manually turn the baby. This procedure has a success rate of about 50-60%. If unsuccessful, a cesarean delivery may be recommended.

By 37 weeks, approximately 3-4% of babies remain in a breech position, meaning their bottom or feet are positioned to come out first rather than their head. While some babies turn on their own even this late in pregnancy, breech presentation at this stage often requires intervention.

External cephalic version (ECV) is a procedure where a skilled healthcare provider uses their hands on your abdomen to gently turn the baby from breech to a head-down position. The procedure is typically performed in a hospital setting under monitoring, and sometimes medication is given to relax the uterus.

The success rate of ECV varies depending on several factors including the amount of amniotic fluid, the position of the placenta, your baby's size, and whether you've given birth before (ECV tends to be more successful in women who have had previous vaginal births). Overall, ECV is successful in about 50-60% of attempts.

ECV is generally considered safe, though there are some risks including temporary changes in the baby's heart rate, premature labor, rupture of membranes, or placental abruption. These complications are rare, and you will be monitored closely during and after the procedure.

What Should I Know About Perineal Tears?

Most women who give birth vaginally experience some degree of perineal tearing. First and second-degree tears are most common and heal well with suturing. Third and fourth-degree tears involving the anal sphincter are less common but may require specialized care. Perineal massage during pregnancy may help reduce the risk of severe tears.

Perineal tears are extremely common during vaginal birth – studies show that approximately 85% of women experience some degree of tearing during their first vaginal delivery. Understanding the types of tears and how they're treated can help reduce anxiety about this aspect of childbirth.

First-degree tears are superficial tears involving only the vaginal mucosa or perineal skin. These are minor and may not require stitches, or they may need only a few sutures. Healing is typically quick and straightforward.

Second-degree tears extend into the perineal muscle but do not involve the anal sphincter. These are the most common type of tear and require suturing under local anesthesia. With proper care, second-degree tears heal well within a few weeks.

Third and fourth-degree tears are less common, occurring in approximately 3-4% of vaginal births. Third-degree tears extend into the external anal sphincter, while fourth-degree tears extend through the anal sphincter into the rectal mucosa. These tears require careful surgical repair and may have longer-term implications for bowel and bladder function.

Reducing the Risk of Severe Tears

While not all tears can be prevented, research suggests that perineal massage during the final weeks of pregnancy may help reduce the risk of severe tears and the need for episiotomy, particularly for first-time mothers. Your healthcare provider can teach you how to perform perineal massage safely.

During labor, techniques such as warm compresses on the perineum, controlled pushing, and certain birthing positions (such as side-lying or hands-and-knees) may help reduce tearing. Your birth attendants will support you during the pushing phase to help protect your perineum.

When Should I Go to the Hospital or Birth Center?

Go to the hospital when contractions are regular (5 minutes apart for 1 hour for first-time mothers, sooner for experienced mothers), if your water breaks, if you have heavy bleeding, if baby's movements significantly decrease, or if you experience severe symptoms like headache or vision changes. Always call ahead before leaving.

Knowing when to go to the hospital is one of the most common concerns for pregnant women in the final weeks. While every labor is different, there are some general guidelines to help you know when it's time to make the trip.

For first-time mothers, the general recommendation is to use the "5-1-1 rule": go to the hospital when your contractions are 5 minutes apart, lasting 1 minute each, for at least 1 hour. This pattern suggests you are in active labor. For women who have given birth before, labor often progresses faster, so you may be advised to come in sooner – such as when contractions are 7-8 minutes apart.

True labor contractions differ from Braxton Hicks in several ways: they become progressively stronger, longer, and closer together over time; they don't go away with rest or position changes; and they are often accompanied by other signs of labor such as bloody show (a pink-tinged mucus discharge) or rupture of membranes.

Signs to Go Immediately

Certain situations require immediate medical attention regardless of your contraction pattern. Go to the hospital right away if:

• Your water breaks – whether as a gush or a slow leak of clear, pale yellow, or greenish fluid
• Heavy vaginal bleeding – more than normal bloody show or period-like bleeding
• Decreased fetal movement – if your baby is moving less than usual or you notice a significant change in their movement pattern
• Severe or constant abdominal pain – especially if it doesn't come and go like contractions
• Severe headache, vision changes, or upper abdominal pain – these could indicate preeclampsia
• Fever over 37.5°C (99.5°F) – which could indicate infection

Before You Leave for the Hospital

Always call the labor and delivery unit before leaving home. The staff can help assess whether it's time to come in based on your symptoms, and they can prepare for your arrival. Have your hospital bag packed and ready, including your prenatal records, identification, insurance information, and any items you want for labor and postpartum.

Consider the distance to your hospital or birth center when planning when to leave. If you have a long drive or anticipate traffic, you may want to leave earlier. Some women arrange to stay with friends or family closer to the hospital as their due date approaches, particularly if they live far away.

How Can I Prepare for Birth at 37 Weeks?

At 37 weeks, final preparations for birth include packing your hospital bag, finalizing your birth plan, installing the car seat, arranging childcare for other children, and reviewing labor signs and coping techniques. Consider perineal massage and continue attending prenatal classes if enrolled.

With just three weeks until your due date (and the possibility that labor could begin at any time), week 37 is an excellent time to finalize your preparations for birth and the postpartum period.

Your hospital bag should be packed and ready by the door. Essential items include your identification and insurance cards, a copy of your birth plan, comfortable clothing for labor and postpartum, toiletries, phone and charger, and going-home outfits for you and baby. Many hospitals provide basic supplies like diapers and pads, but check with your facility about what to bring.

If you haven't already, now is the time to install your infant car seat. Many fire stations and hospitals offer car seat inspection services to ensure it's installed correctly. Remember, you cannot take your baby home from the hospital without a properly installed car seat.

Review your birth plan with your partner and healthcare provider. While flexibility is important since birth rarely goes exactly as planned, having discussed your preferences for pain management, labor positions, delayed cord clamping, skin-to-skin contact, and feeding plans helps ensure your wishes are known.

Mental Preparation

The final weeks of pregnancy can bring a mix of excitement and anxiety. It's completely normal to have concerns about labor, birth, and caring for a newborn. If you're feeling overwhelmed, talk to your partner, a trusted friend, or your healthcare provider about your concerns.

Many women find it helpful to practice relaxation techniques such as deep breathing, visualization, or mindfulness. These techniques can be valuable coping tools during labor and can help reduce anxiety in the waiting period. If you've been attending prenatal classes, review the techniques you've learned.