The First Trimester

Physical Changes: When we think of a pregnant woman, we envision an expanding middle. During the first trimester, you won't see much of a bump, but you will notice growth in another area -- your breasts. They're apt to be tender and larger. One of your first pregnancy purchases might be a larger bra. From early pregnant, your breasts change and develop to produce milk.

Weight Gain: If you started your pregnancy at a normal weight, you'll probably gain somewhere around five pounds. The baby's only responsible for a few ounces. Amniotic fluid, extra blood volume and breast tissue make up the rest. Not everyone gains weight the first weeks of pregnancy. Some women actually lose due to morning sickness.

Your Baby's Development

Fertilization: About two weeks after the first day of the last menstrual period, your ovary releases an egg. It met up with a sperm in the fallopian tube. The fertilized egg has the all the chromosomes needed to determine height, hair color, sex and more. The egg begins to divide, and begins its trip toward the uterus.

Implantation: Your microscopic baby grows and doubles in size every day. Five to seven days later, it burrows into the lining of the uterus. The placenta and umbilical cord begin to form.

Week 4: You've misses your period. Your baby, called an embryo at this stage, measures about 1/100 of an inch long. He or she already has a spinal cord, and is dividing into three layers that will become the different organs and systems in the body.

Week 6: Your baby's growth rate is amazing! The embryo lengthened from 1/100 of an inch to about 1/6 inch. Tiny limb buds appear. Soon you'll be able to see legs and arms, Blood is being pumped through the fetal circulation, and a heartbeat can be seen on an ultrasound. The heart has begun beating and pumping blood. If you have a dating ultrasound, now, you'll probably be able to see a fast blip during the scan. That's your baby's heartbeat!

Second Month: At the beginning of this month, the baby is about 1/2 inch long and weighs a fraction of an ounce. By the end of the second month, all the major body organs and body systems have begun to develop. Your baby, now called a fetus, looks like a tiny human. The baby bean's now a little over an inch long and still weighs less than an ounce.

Third Month:By the end of this month, the organs and other systems are completely formed. Tiny hands, complete with fingers flail, legs kick, toes wiggle, and the mouth opens and closes. He or she is still too small for you to feel the movement. By the end of this month, the baby will be about 4 inches long and weigh just over an ounce.

Prenatal Appointments

Once you suspect (or confirm) that you're pregnant, give your health care provider a call. Most will want to see you within 12 weeks of your last normal menstrual period. If you're over 35, a high risk pregnancy or a teen, your midwife or doctor will probably schedule an earlier appointment so you can receive more intensive support. In the first trimester, you'll probably have a visit every four to six weeks, with optional ultrasounds for dating and screening.

The first prenatal appointment: The office will schedule you to come in as early as six weeks or as late as 13 weeks.

A dating ultrasound: If your cycles are irregular or you're not certain of your last menstrual period, your provider might suggest a dating ultrasound. Be sure to ask for copy of baby's first picture for your scrapbook!

The First Trimester Screening consists of an ultrasounds and a blood test. The data combines to let you know the risks that your baby has a genetic condition. If you decide to go ahead with diagnostic testing, a chorionic villi sampling can be scheduled between between 8 and 12 weeks or an amniocentesis scheduled between 15 and 21 weeks.