33 weeks pregnant: baby development
Immune system development
The fetal immune system is developing at a rapid pace with antibodies passing from your body to your baby so he can fight diseases and infections after birth .
Bone and skull development
The bone development continues into the 33rd week with the gradual hardening of the fetal skeleton . The bones in his skull are yet to fuse together, remaining in such a way until birth to make it easier for your baby’s head to pass through the birth canal. In fact, the skull bones do not fuse entirely until one reaches early adulthood, to allow proper brain expansion and tissue growth .
Internal organ development
These last few weeks have been vital in the growth of the fetal respiratory system with the lungs now mature enough to allow your baby to breathe on his own if you were to give birth now. The chemical agent surfactant produced by your baby’s body helps to keep the airways (respiratory tracts) open, assisting in respiration . However, babies born during the 33rd week are kept in ventilation for a few weeks after birth so their lungs could pump oxygen and carbon dioxide at a steady pace.
By the 33rd week, there is almost 1 liter of amniotic fluid surrounding your baby, protecting him from any outside impact. The volume of amniotic fluid also signifies proper functioning of the fetal kidneys as your baby should be passing about 500 ml of urine in a day .
Other organs and systems like the brain and nervous systems have already completed their development in the womb  while the fetal liver is storing iron to help your baby grow after he enters this world .
Your baby’s skin appears smoother and more opaque with the growth of the fat layer underneath . He already looks like what he will on his birth day; however, he still has a considerable amount of weight to gain.
How big is your baby?
The baby is around 17.2 inches (43.68 cm) long by the 33rd week , weighing just over 4 pounds (1.8 kg), about the size of a pineapple .
Your baby does not have much space for those jerky movements you have been feeling in the early third trimester. The fetal activity levels now depend on your surroundings, external noises as well as when and what you eat . Your baby now shows newborn-like behaviour, opening his eyes when awake and even differentiating between night and day. The gradually thinning uterine walls allow more light to penetrate the womb, letting your baby know when it is daytime .
He should already be in a proper head down position for birth; although, do not worry if he is still in a breech position as there is still time for him to rotate in place. Your doctor will carefully monitor your baby’s position in these last few weeks to make sure he comes into the birth position before delivery .
33 weeks pregnant: weight gain, belly and body changes
By this week, you can feel the top of the uterus around 5 inches over your bellybutton . You have probably already gained about 22 pounds to 28 pounds by this point, with the ideal weight gain level from here on being 0.5 to 1 pound a week .
The hormone relaxin is produced in pregnancy by your body to loosen the pelvic joints and muscles to prepare your body for childbirth. But, the functioning of this hormone is not restricted within the pelvic area as it also relaxes the muscles and joints in other parts of the body, leading to pain and discomfort.
Twin pregnancy week 33 weight gain
Women carrying multiples should gain 1.5 pounds per week throughout the third trimester . Their weight gain usually ranges around 30 pounds by the 33rd week. Maintaining a healthy diet with lots of iron, calcium and folic acid is essential to provide both babies with enough nutrients for proper mental and physical growth.
33 weeks pregnant tests and ultrasound
An ultrasound might be performed to assess the amniotic fluid levels or to check the position of your baby in the uterus in case your doctor suspects a breech baby .
Most women do not require any more medical exams and screening tests following the 28th week complete blood count performed to detect gestational diabetes (glucose tolerance ) and anemia . Those with low iron levels shown by their blood test are prescribed supplements and asked to come back for another blood count within a few more weeks.
Your doctor might order a screening test like amniocentesis during late pregnancy in case of a detected infection or complication like rupture or membranes 
Pregnancy week 33 signs and symptoms
- Indigestion and heartburn
- Braxton Hicks contractions 
- Leg cramps
- Tiredness 
- Restless leg syndrome and insomnia 
- Emotional changes, depression and anxiety
- Round ligament pain
- Tailbone and pelvic pain
- Joint (knees, jaws, hips) and back pain
- Clumsiness and pregnancy brain
- Shortness of breath and chest pain due to the growing uterus putting pressure on your lungs and ribs 
- Loss of appetite
- Tingling sensation or numbness in the hands and fingers (carpal tunnel syndrome) 
- Headaches and dizziness
- Itchy skin, especially around the expanding belly, breasts, back and thighs 
- Stretch marks and itchy rashes mainly on the belly 
- Varicose veins and hemorrhoids
- Edema or swelling of the ankles and feet 
When to call the doctor
- Uterine contractions getting more frequent over time accompanied by mucus discharge (losing the mucus plug), feeling pelvic pressure, bleeding/spotting, increased vaginal discharge, menstrual-like cramps, throbbing lower back pain (around the kidneys), flu-like symptoms (diarrhea and vomiting) and nausea (might be signs of preterm labor) 
- Severe itchiness of the hands, palm and feet that refuses to go away with any home treatment measure (might indicate a rare liver disease, intrahepatic cholestasis of pregnancy) 
- Constant headache, extreme fatigue, nausea, upper abdominal pain and lightheadedness along with sudden yet considerable nosebleeds, vision changes, edema (face and hands) and weight gain (might indicate high blood pressure or preeclampsia) 
- Pain or burning during urination and dark or cloudy urine accompanied by lower back pain, thick, egg-white, greenish or yellowish jelly-like discharge, nausea and pain or bleeding after intercourse (might indicate infectious conditions like UTI , a kidney or yeast infection )
- Extreme thirst and dry mouth along with abnormally frequent urge to urinate and yet passing little urine, sudden blurred vision, headache, abdominal pain (especially in the right side) tiredness and nausea (might indicate gestational diabetes) 
- Sudden bright red bleeding with or without lower stomach or back pain (might indicate placenta previa or a low lying placenta) 
- Lots of clear or yellowish thin watery discharge (might indicate leaking amniotic fluid)
- Unilateral swelling or one foot or ankle more swollen than the other (might indicate a blood clotting disorder)
Tips for a healthy pregnancy and baby
- Drinking lots of fluids as it helps to manage common symptoms like constipation and water retention by flushing waste materials and toxins from your system 
- Doing regular kick counts to keep track of all sorts of fetal movements (small kicks, pokes and hiccups) to ensure proper fetal health
- Doing regular pelvic floor exercise (kegels) to strengthen the pelvic muscles and better support the weight of your growing baby; it also helps manage incontinency (leaking urine) after delivery 
- Following a diet consisting lots of omega-3 fatty acids or DHA as they are essential for the fetal vision and brain development while a diet rich in DHA is also believed to minimize the risks of preterm labor and postpartum depression; FDA recommends including 8-12 ounces of fish and shellfish with high DHA and low mercury content, such as salmon, tilapia, shrimp and catfish, in your weekly diet (fresh tuna, shark and swordfish should be avoided as they might contain certain toxins) 
- Doing prenatal yoga or following a light exercise routine that includes going for a short walk 2 times a day or taking a swim to fight back and joint pain as well as to manage constipation and prepare your body for childbirth 
- http://kidshealth.org/parent/nutrition_center/staying_fit/exercising_pregnancy.html [/ref]