Pregnancy Week 3

Woman who is 3 weeks pregnant

Congratulations! The third week of pregnancy is usually when ovulation and implantation occur. Here’s what you should know about your body this week.

Pregnancy Week 3: How is pregnancy calculated?

There is always a lot of confusion when discussing the way in which pregnancy is calculated. Since most women do not know when they conceived, pregnancy is always determined from the first day of your last menstrual period (LMP). Given that this is the way pregnancy is calculated, your pregnancy will last around 40 weeks. For more information on how pregnancy is measured, please see our information on calculating your dates.

Pregnancy Week 3: What changes are occurring with your body?

Many women do not notice any changes, but some women experience mild cramping and increased vaginal discharge.

During ovulation the ovaries release a mature egg that begins to travel to the uterus through the fallopian tubes. Sperm travel through the uterus to fertilize the egg within the fallopian tube. Only a single sperm fertilizes an egg. Both the sperm and the egg contain 23 chromosomes that will combine to make up the zygote which contains a total of 46 chromosomes. At conception, your baby’s gender, eye color, hair color, and much more has already been determined.

The zygote continues to travel through the fallopian tubes into the uterus where it will attach itself to the uterine wall. For additional information on ovulation please read Ovulation Frequently Asked Questions or Understanding Ovulation.*

Pregnancy Week 3: What is happening with your baby?

The blastocyst is growing and multiplying rapidly at this point. Part of the blastocyst will become the placenta, which will produce hCG (human chorionic gonadotropin). hCG is the pregnancy hormone that is detected by pregnancy tests.

Amniotic fluid is also collecting around the cells that will protect and cushion your baby throughout your pregnancy. A lot of basic growth is occurring at this time, including the beginning development of the brain, spinal cord, heart, and gastrointestinal tract.*

Pregnancy Week 3: How big is your baby?

The embryo in your body is very small and actually looks more like a group of cells than a baby. It is the size of the head of a pin and approximately .0019 inches (.048 mm) long. It could be seen by the human eye if it were not inside your body.*

Pregnancy Week 3: What should you plan for this week?

Exercise is important during pregnancy.Consult your healthcare provider before beginning or continuing an exercise routine. In most circumstances, if you are already on an exercise routine, then you likely can continue your active lifestyle. Check out our list of the top recommended exercises during pregnancy.

Remember that your baby is taking in everything that you do, both good and bad. You want to avoid alcohol, illegal drugs, certain medications, certain foods, caffeine, and smoking.

Nutrition is also important this early in pregnancy. Folic acid and other essential nutrients and vitamins are necessary for fetal growth and a healthy pregnancy. Eating a balanced diet high in protein and calcium is also beneficial for both you and the baby. If you have questions, check with your health care provider to see what dietary recommendations they encourage.

Pregnancy Week 3: Tips for making your pregnancy better

Your body is beginning to go through some drastic changes, and this can be an overwhelming time. Make sure that you do not neglect getting adequate rest and nutrition. Take time to relax and enjoy being pregnant.

Pregnancy Week 3: Tips for mom’s partner

Both you and your partner may have fears that begin to emerge now or during the next several weeks, even if this was a planned pregnancy. Be open with each other and discuss these with one another. Ask questions so that she feels you want to be involved in the pregnancy. Take time to plan little ways that you can support her and surprise her over the next 37 weeks.