31 Weeks Pregnant: Baby Development & What to Expect

How Is My Baby Developing at 31 Weeks?

At 31 weeks, your baby weighs approximately 1.5 kilograms (3.3 pounds) and measures about 41 centimeters (16 inches) from head to heel. The brain is developing rapidly with billions of neural connections forming, all five senses are now functional, and baby is accumulating white fat to regulate body temperature after birth.

Week 31 represents a critical period of fetal development, particularly for the brain and nervous system. Your baby's brain is now developing at an unprecedented rate, with the cerebral cortex maturing rapidly. The brain's surface area is increasing as more folds (gyri and sulci) form, which allow for greater cognitive capacity and neural processing power. Research published in developmental neuroscience journals indicates that during this period, the fetal brain forms approximately 250,000 new neurons every minute.

The coordination between your baby's brain and body is becoming increasingly sophisticated. Your baby can now process information from all five senses - sight, hearing, taste, smell, and touch. While still in the womb, your baby can respond to light filtering through your abdomen, react to sounds (including your voice and heartbeat), taste the amniotic fluid which carries flavors from your diet, and demonstrate tactile responses to pressure on your belly.

Fat accumulation is another crucial development occurring at 31 weeks. Your baby is transitioning from the thin, translucent appearance of earlier pregnancy to the plumper, more rounded look of a newborn. This white adipose tissue serves multiple essential functions: it provides insulation to maintain body temperature after birth, serves as an energy reserve for the demanding first days of life, and gives your baby that characteristic "baby fat" appearance. Your baby is now gaining approximately 200 grams (about half a pound) per week, with much of this weight coming from fat deposition.

Lung Development at Week 31

Your baby's lungs continue to mature, producing increasing amounts of surfactant - a substance that prevents the tiny air sacs (alveoli) in the lungs from collapsing. While premature babies born at 31 weeks often survive with medical support, they typically require assistance with breathing because surfactant production is not yet at optimal levels. The lungs will continue maturing until around 36-37 weeks of pregnancy.

During this week, your baby is also practicing breathing movements more regularly. These practice breaths involve the diaphragm contracting and relaxing, which strengthens the respiratory muscles and prepares your baby for the crucial first breath after birth. You might notice these breathing movements as rhythmic, hiccup-like sensations, which are completely normal.

Baby's Sleep-Wake Cycles

By 31 weeks, your baby has developed distinct sleep-wake cycles. Research using fetal monitoring has shown that babies at this gestational age spend most of their time in quiet sleep (similar to non-REM sleep in adults), with periods of active sleep (comparable to REM sleep) and short intervals of wakefulness. You may notice that your baby's activity patterns follow a predictable rhythm, often becoming more active in the evening when you are resting.

During active sleep, your baby's brain is processing the sensory information gathered during waking periods. This is thought to be important for memory consolidation and brain development. The distinction between sleep states is a sign of neurological maturation and indicates that your baby's central nervous system is developing normally.

What Changes Are Happening to My Body at 31 Weeks?

At 31 weeks pregnant, your body is adapting to accommodate your growing baby. Common changes include your uterus expanding to about 11 centimeters above your navel, increased blood volume by 40-50%, shortness of breath as your uterus presses against your diaphragm, and ligament relaxation preparing your pelvis for birth.

Your body continues to undergo remarkable transformations during week 31 of pregnancy. The uterus, which started pregnancy about the size of a pear, now extends approximately 11 centimeters (about 4.3 inches) above your belly button. This expansion places pressure on surrounding organs and tissues, accounting for many of the physical symptoms you may be experiencing. The fundal height - the distance from your pubic bone to the top of your uterus - is approximately 31 centimeters, roughly correlating with the number of weeks pregnant you are.

Your blood volume has increased by approximately 40-50% compared to pre-pregnancy levels to support both your body and your growing baby. This increased blood volume means your heart is working harder, pumping more blood with each beat. Your resting heart rate may be 10-20 beats per minute higher than before pregnancy. While this cardiovascular adaptation is normal, it can contribute to feelings of fatigue and shortness of breath.

The hormone relaxin, which has been present throughout your pregnancy, continues to work on loosening the ligaments and joints throughout your body. This is particularly noticeable in your pelvis, where the symphysis pubis (the joint at the front of your pelvis) and sacroiliac joints (at the back of your pelvis) are becoming more flexible to facilitate childbirth. While this hormonal effect is essential for delivery, it can contribute to pelvic pain, back discomfort, and a "waddling" gait that many women experience in the third trimester.

Weight Gain at 31 Weeks

By 31 weeks, most women have gained between 9-13 kilograms (20-29 pounds) total, though this varies significantly based on pre-pregnancy weight, body type, and individual factors. The recommended weight gain during the third trimester is approximately 0.5 kilograms (about 1 pound) per week for women who started pregnancy at a normal weight. This weight is distributed among the baby, placenta, amniotic fluid, increased blood volume, breast tissue, uterine enlargement, and maternal fat stores.

If you are concerned about your weight gain - whether it seems too much or too little - discuss this with your healthcare provider. They can assess your individual situation and provide personalized guidance. Remember that the goal is a healthy pregnancy for both you and your baby, and appropriate weight gain supports this outcome.

What Symptoms Are Common at 31 Weeks Pregnant?

Common symptoms at 31 weeks include Braxton Hicks contractions, shortness of breath, frequent urination, heartburn, difficulty sleeping, swollen feet and ankles, back pain, and increased vaginal discharge. Most symptoms are normal third-trimester experiences, but contact your healthcare provider for severe or concerning symptoms.

The third trimester brings a unique set of symptoms as your body continues to adapt to your growing baby. Understanding which symptoms are normal - and which warrant medical attention - can help you navigate these final weeks of pregnancy with greater confidence. Here is a comprehensive look at what you might experience at 31 weeks.

Braxton Hicks Contractions

Braxton Hicks contractions, often called "practice contractions," become more noticeable during the third trimester. These irregular contractions feel like a tightening or hardening of your abdomen and typically last 30 seconds to 2 minutes. Unlike true labor contractions, Braxton Hicks are usually painless or only mildly uncomfortable, do not increase in frequency or intensity, and often stop when you change position, walk around, or drink water.

These practice contractions serve an important purpose: they help tone your uterine muscles and may contribute to cervical ripening (softening and thinning) in preparation for labor. While experiencing several Braxton Hicks contractions per day is normal, contact your healthcare provider if you have more than four to six contractions per hour, if they become regular and increasingly painful, or if they are accompanied by other symptoms like vaginal bleeding or fluid leakage.

Shortness of Breath

Many women experience breathlessness at 31 weeks as the expanding uterus pushes upward against the diaphragm, limiting lung expansion. This is particularly noticeable during physical activity, when lying flat, or after eating a large meal. Your body compensates by increasing your respiratory rate slightly, and you may find yourself taking more shallow breaths.

To manage shortness of breath, try sleeping with extra pillows to prop yourself up, eating smaller and more frequent meals, practicing good posture to maximize lung capacity, and taking breaks during physical activities. As your baby drops lower into your pelvis in the final weeks of pregnancy (a process called "lightening" or "engagement"), you may experience some relief from breathlessness.

Sleep Difficulties

Getting comfortable at night becomes increasingly challenging at 31 weeks. Between your growing belly, frequent trips to the bathroom, leg cramps, heartburn, and general discomfort, quality sleep can feel elusive. Many pregnant women experience vivid dreams and more frequent nighttime awakenings during the third trimester.

Sleep strategies that may help include sleeping on your left side with a pillow between your knees, using a full-body pregnancy pillow for support, establishing a relaxing bedtime routine, avoiding fluids for two hours before bed (while staying well-hydrated during the day), and avoiding heavy or spicy foods close to bedtime. While "sleeping when baby sleeps" is advice more commonly given to new parents, taking daytime naps during pregnancy can help compensate for disrupted nighttime sleep.

How Often Should I Feel My Baby Move at 31 Weeks?

At 31 weeks, you should feel your baby move regularly throughout the day. Most healthcare providers recommend counting at least 10 movements within 2 hours during your baby's active periods. Contact your healthcare provider immediately if you notice a significant decrease in movement or if your baby stops moving.

Monitoring fetal movement is one of the most important things you can do during the third trimester. Your baby's movements are a reassuring sign of wellbeing, and changes in the pattern of movement can sometimes indicate that your baby needs attention. By 31 weeks, you should be familiar with your baby's typical activity patterns - when they are most active, what their movements feel like, and their general rhythm of sleep and wakefulness.

While every baby is different, most healthcare providers recommend doing daily "kick counts" starting around 28 weeks of pregnancy. The most common method involves choosing a time when your baby is typically active (often after a meal or in the evening), lying down or sitting comfortably, and counting how long it takes to feel 10 distinct movements. Most babies will move 10 times within 1-2 hours during their active periods.

At 31 weeks, your baby's movements may feel different than earlier in pregnancy. Because there is less room in the uterus, you may notice more rolling, stretching, and shifting rather than the dramatic kicks and punches of the second trimester. Hiccups, which feel like rhythmic, repetitive movements, are also common and completely normal. What matters most is not the type of movement but the consistency of your baby's individual pattern.

What Prenatal Care Do I Need at 31 Weeks?

At 31 weeks, you typically have prenatal visits every 2 weeks. Standard checks include blood pressure measurement, urine testing, fundal height measurement, baby's heartbeat monitoring, and discussing your birth plan. Additional tests may be recommended based on individual risk factors.

During the third trimester, prenatal visits become more frequent to closely monitor both your health and your baby's wellbeing. Most healthcare providers recommend appointments every two weeks from weeks 28-36, then weekly from week 36 until delivery. These regular check-ups allow your provider to identify and address any concerns promptly.

At each visit, your healthcare provider will typically measure your blood pressure and weight, test your urine for protein and glucose (which can indicate conditions like preeclampsia or gestational diabetes), measure your fundal height to assess your baby's growth, listen to your baby's heartbeat, and discuss any symptoms or concerns you may have. Your provider may also check the position of your baby, though many babies are still moving freely at 31 weeks and have not yet settled into their final birth position.

Tests You May Have at 31 Weeks

Depending on your individual situation and risk factors, your healthcare provider may recommend additional tests during this period of pregnancy. These might include:

• Group B Streptococcus (GBS) screening: Usually done between weeks 36-37, but your provider may discuss this upcoming test
• Non-stress test (NST): Monitors baby's heart rate in response to movement
• Biophysical profile (BPP): Combines NST with ultrasound assessment
• Blood tests: To check for anemia or other conditions
• Ultrasound: May be recommended to check baby's growth, position, or amniotic fluid levels

This is also an excellent time to discuss your birth preferences with your healthcare provider. Topics might include pain management options during labor, your preferences for medical interventions, who you want present during delivery, and any cultural or personal considerations. While flexibility is important (because labor and delivery can be unpredictable), having a general plan can help you feel more prepared and in control.

When Should I Seek Medical Care at 31 Weeks?

Seek immediate medical attention at 31 weeks if you experience regular contractions (more than 4-6 per hour), vaginal bleeding, fluid leaking from your vagina, severe headache with vision changes, severe abdominal pain, significantly decreased fetal movement, or signs of preeclampsia including sudden swelling and high blood pressure.

While most third-trimester symptoms are normal parts of pregnancy, certain signs and symptoms require immediate medical attention. Being aware of these warning signs can help you get timely care when it matters most. Remember that your healthcare team would always rather assess a concern that turns out to be nothing than miss something important.

Signs of Preterm Labor

At 31 weeks, your baby would benefit from every additional week of development in the womb. Signs of preterm labor include regular contractions occurring every 10 minutes or more frequently, menstrual-like cramping that comes and goes, low dull backache (different from your usual back pain), pelvic pressure that feels like baby is pushing down, change in vaginal discharge (especially if watery, mucus-like, or bloody), and a general feeling that "something is wrong."

If you experience any of these signs, contact your healthcare provider or go to your birthing facility immediately. Early intervention can sometimes stop or slow preterm labor, and if delivery is imminent, your baby can receive medications to support lung development and other important functions.

Signs of Preeclampsia

Preeclampsia is a serious pregnancy complication characterized by high blood pressure and signs of organ damage, usually to the liver and kidneys. Warning signs include severe headache that does not respond to rest or medication, visual disturbances such as blurry vision, seeing spots, or light sensitivity, upper abdominal pain (especially on the right side), sudden swelling of the face, hands, or feet, and nausea or vomiting in the third trimester.

If you experience these symptoms - especially if multiple symptoms occur together - seek immediate medical care. Preeclampsia can progress rapidly and, in severe cases, can be life-threatening for both mother and baby. Early detection and management significantly improve outcomes.

How Can I Prepare for Birth at 31 Weeks?

At 31 weeks, important birth preparations include completing childbirth education classes, touring your birthing facility, finalizing your birth plan, preparing your hospital bag, installing your car seat, and discussing maternity leave with your employer. This is also a good time to arrange support for after baby arrives.

With approximately 9 weeks until your due date, now is an excellent time to focus on practical preparations for your baby's arrival. While every pregnancy and birth experience is unique, taking steps to prepare can help you feel more confident and ready for the transition to parenthood.

If you have not already done so, consider enrolling in a childbirth education class. These classes cover topics such as the stages of labor, pain management options, breathing and relaxation techniques, what to expect during delivery, and newborn care basics. Many hospitals and birthing centers offer these classes, and virtual options are also available. Partners and support persons are typically encouraged to attend, which can help them understand how to best support you during labor and delivery.

Practical Preparations

Your hospital bag should be mostly packed by now, though you can leave out items you use daily and add them when the time comes. Beyond the essentials mentioned earlier, consider including comfortable labor clothes or a nightgown, nursing bras if you plan to breastfeed, going-home outfits for you and baby, snacks and drinks for your support person, entertainment options like books or music, and any items that bring you comfort (such as a favorite pillow or essential oils).

Your baby's car seat should be properly installed before you go into labor. Most hospitals will not discharge a newborn without a car seat, and trying to figure out installation while caring for a newborn is challenging. Many fire stations and hospitals offer free car seat installation checks - take advantage of these services to ensure your seat is correctly installed.

Consider practical arrangements for the postpartum period as well. This might include preparing and freezing meals, arranging help with housework or childcare for older children, setting up a comfortable nursing or feeding area, organizing baby supplies, and discussing parental leave plans with your employer.