Stages of Pregnancy: Trimester by Trimester

• Embryo size doubles between nine and twelve weeks.
• All major organs are forming, but they are not fully developed yet.
• Eyes and ears are growing.
• The heart is beating strongly.
• At 12 weeks your baby is 2.5 inches long and weighs about 0.64 ounces.
• The head is becoming more rounded and the face is completely formed.
• Toes and fingers are formed and nails are beginning to grow.
• The baby may be very active, but you cannot feel movement yet.
• Male and female genitalia are recognizable by 12 weeks.

Your health care provider may order the Quad screen, a simple blood test. Other laboratory testing may also be ordered such as a complete blood count to test for the presence of anemia.

The American College of Obstetricians and Gynecologists (ACOG) recommends that all pregnant women be offered a screening test for Down syndrome, regardless of the woman’s age. Screening may be a maternal blood test done in the first trimester along with ultrasound, or it can be a maternal blood test done in the second trimester without ultrasound, or a combination of both.
ACOG also recommends that all pregnant women be offered invasive diagnostic testing by chorionic villus sampling (CVS) or genetic amniocentesis, regardless of age. These procedures obtain cells/tissue that allow for highly accurate diagnosis of Down syndrome or other genetic variations. However, CVS and amniocentesis are invasive and carry a small risk of causing a miscarriage.
Noninvasive Testing for Women at Increased Risk for Chromosome Abnormalities
A noninvasive blood test is now available for women with increased risk indicators for fetal chromosome variations. This test detects an increased amount of DNA material (mother and baby) that is circulating in your blood. This can predict a chromosomal abnormality such as Down syndrome (trisomy 21) in your baby. The increased risk factors include one or more of the following:

• Advanced maternal age
• Personal/family history of chromosomal abnormalities
• Fetal ultrasound abnormality suggestive of chromosomal abnormalities
• Positive serum screening test

Amniocentesis, or CVS (chronic villus sampling) may be performed on many factors, please discuss with yor health care provider. This is a procedure in which a small sample of amniotic fluid is drawn out of the uterus through a needle inserted in a pregnant woman's abdomen. The fluid is then analyzed to detect genetic abnormalities in the fetus or to determine the gender of the fetus.

• Sign up for childbirth classes and other classes that are of interest to you, such as breastfeeding, baby care, infant CPR. Refer to Childbirth Education to find available classes.
• Read about labor and childbirth. Ask your OB/midwife about their particular philosophies regarding labor and birth. Explore information about Your Birth Plan.

• At 16 weeks your baby is about 6.3 inches long and weighs .08 pounds. It is kicking and moving about frequently. You may be feeling the baby moving. If this is your first baby, you are likely to feel the first movements a bit later.
• At 20 weeks the baby is swimming in a large amount of amniotic fluid growing rapidly, both in length and weight and is now 9.8 inches and weighs about .75 pounds. The baby is very active. You will probably notice that there are times when your baby seems to be asleep and other times when he's moving a lot.
• At 24 weeks your baby is about 12.5 inches long and weighs 1 pound, 1.6 ounces. You may feel different parts of the baby's body through your abdominal wall. Your uterine muscle is stretching and you may feel occasional pain along the sides of your abdomen (round ligament pain). The top of your uterus (the fundus) reaches to just above your navel.

Read about baby care.

• Talk with your caregiver as you choose whether to breastfeed or bottle-feed. Based on your breast exam you may be encouraged to consult a lactation specialist prior to the birth of your baby.
• Finish all childbirth, breastfeeding, baby care, and other classes sooner rather than later. Babies have their own time schedules and sometimes may arrive early.
• Read about labor and childbirth and develop your birth plan. See the Birth Plan Worksheet in cover pocket of this booklet.
• At 30 weeks your baby's weight is now about 3 pounds, 11 ounces and measures about 15.8 inches in length. 
• You may be feeling pressure on your diaphragm, stomach, and intestines as your uterus and baby grow.

• At 36 weeks, the baby is almost fully mature and is now about 19.7 inches long and weighs anywhere from 5 pounds, 8 ounces to 9 pounds, 14 ounces.
• The baby may descend into your pelvis (engagement) preparing for birth.
• Once the baby has engaged, you may find that your breathing becomes easier and the pressure on your diaphragm is less.
• Your baby is putting on weight at a rate of almost 8 ounces per week until delivery.
• When the baby is awake, his eyes are open and he can differentiate between light and dark.;
• Labor may start at any time now. Do not worry if your baby is not born exactly on his due date. The due date is only an estimate. Only 5% of babies are born exactly on their due dates. The long-awaited day is near and soon you will be holding your baby in your arms.