You are almost at the end of the third month of your pregnancy, and the risk of miscarriage has decreased dramatically . Read all about your baby’s development, your body changes as well as the abnormal symptoms to watch out for this week.
Baby development in week 12
Nervous system development
The period between weeks 12 and 18 is vital for your baby’s brain development . The pituitary gland begins producing hormones in the 12th week while the brain’s nerve cells develop and multiply at a fast pace .
Internal organ development
The intestines (moved into your baby’s stomach last week) start to contract and relax repeatedly to practice healthy digestion so they can function properly after birth . The lungs continue their growth, taking part in primitive breathing while the vocal cords start to form . The pancreas is developed enough to produce insulin for your little one  with the kidneys starting to work on urine production .
The hands and feet are fully developed with your baby already able to wiggle those tiny fingers and toes . He may also start sucking on his thumb this week , which means the reflexes are starting to develop.
The face already looks like that of a newborn (only in miniature) with the eyes and ears almost in place . The hair follicles start growing special downy hair referred to as lanugo which helps your baby to stay warm .
The skeletal system starts out as a cartilaginous structure which begins to ossify or turn into hard bone around this week . The bone marrow also starts producing infection fighting white blood cells .
This week, the placenta has taken over the job of filtering oxygen and all the necessary nutrients for proper fetal growth .
12 weeks pregnancy baby size
This week, your baby measures about 2 inches (5 cm) in size, weighing around 0.5 oz (14 gm) ; almost as big as a plum .
Body changes during 12th week of pregnancy
The pressure on your bladder gradually lifts as the uterus starts moving upward from your pelvis . Your belly can now provide more space for the uterus to grow as your doctor can already feel its top (called the fundus) in your lower abdomen, just above the pubic bone .
What does 12 week pregnancy look like?
First time moms do not usually start showing enough at this stage for others to know that they are pregnant. However, the gradually thickening belly often makes non-restrictive loose clothing seem more comfortable than the regular jeans and skirts . Overweight women, second time mothers and those carrying twins are likely to start showing a bit early .
12 weeks pregnant ultrasound
Most women get their first ultrasound scan during week 12 . With the genital organs almost fully developed, your baby’s gender may be determined this week on an ultrasound image . However, sex determination might be erroneous at this early stage.
An ultrasound will also show your baby stretching, kicking, twisting and turning within the uterus . But, he is still too small for you to feel these movements. You can hear the fetal heartbeat on a Doppler device .
Screening tests in pregnancy week 12
Certain blood tests may be performed during your prenatal checkup to determine the risks of genetic disorders like Down’s syndrome. Your doctor may recommend you to take a nuchal translucency scan which involves measuring the fluid levels behind your baby’s neck . Other prenatal screening tests like amniocentesis and chorionic villus sampling (CVS) may be performed within a few weeks to confirm any fetal abnormalities .
12 week pregnancy signs and symptoms
You may notice your energy levels increasing to some extent this week  while the symptoms of frequent urination  and morning sickness begin to subside as well. However, it is perfectly normal to continue having the symptoms of tiredness, nausea, gas, bloating, heartburn and indigestion due to the increased pregnancy hormone levels. Other common 12th week signs include:
- Blurred vision (due to the retained fluid in your body, which changes the pressure within your eyeball as well as thickens the cornea and lens) 
- Excessive saliva
- Headaches (migraine) and dizziness 
- Abdominal and back pain (upper and/or lower)
- Joint and hip pain
- Improved appetite (now that you are about to enter the second trimester) 
- Depression and emotional changes (although, some women may find themselves in reasonably high spirits)
- Increased vaginal discharge (due to the pregnancy hormones and fluid retention)
- Dry itchy skin, especially around the expanding belly and breasts (due to the increased estrogen levels) 
- Sleep disturbances (insomnia)
- Round ligament and pelvic pain (due to the growing uterus)
- Darkening areola and irregular dark marks on the neck and face (mask of pregnancy or chloasma) 
- Appearance of a vertical dark line (linea nigra) 
- Mild shortness of breath 
When to call the doctor?
The symptoms to watch out for are quite the same from last week with the most alarming ones including:
- Severe headache with or without symptoms like blurred vision, sudden swelling of the hands and feet and chest pain (might indicate preeclampsia) 
- Heavy bleeding along with severe lower abdominal and back pain or cramping (might indicate a miscarriage or ectopic pregnancy)
- Extremely blurred vision (might indicate hypertension or gestational diabetes) 
- Fever (over 102 °F) that refuses to go away
- Clear or straw colored thin, odorless discharge (might indicate leaking amniotic fluid)
- Intense and frequent urge to urinate along with pain or burning sensation while urinating (might indicate a bacterial infection like UTI) 
- Severe diarrhea or nausea with vomiting over 3-4 times a day (increases the risks of weight loss and dehydration) 
- Severe back pain along with leaking urine and pain during urination (might indicate a retroverted uterus) 
Tips for a healthy pregnancy and baby
- Following a light exercise routine or join an antenatal yoga class to prepare your body for the coming changes 
- Eating smaller meals and snacks (preferably six) instead of the 3 large ones
- Drinking plenty of fluids to stay well hydrated (avoid fizzy drinks, alcohol and caffeine)
- Drinking fluids before or after meals instead of with them 
- Avoiding greasy, fatty and acidic foods to reduce heartburn 
- Making sure to use oil-free non-comedogenic makeup if you need to cover those dark marks and acne on your face 
- Following a healthy diet rich in calcium, protein and vitamins to fulfill your and your baby’s nutrition requirement
- Consulting your doctor regarding the safety of using a moisturizer if you are experiencing dry, itchy skin [skin care in pregnancy]
- Avoiding getting an x-ray unless absolutely necessary to protest the baby from the harmful radiation
- Avoiding jerky movements and actions that might hurt the baby (e.g. riding a bike, jogging and riding roller coasters)
- Consulting your doctor if you are planning to dye your hair [dyeing your hair in pregnancy]
- http://www.babycenter.com/0_shortness-of-breath-during-pregnancy_219.bc [/ref]