Your Pregnancy Week 4

Reviewed by James Brann, MD
Learn about 
your symptoms and changes during the 4th week of pregnancy.

Your Baby

During pregnancy week four your baby is still very tiny, probably less than .04 inches long. That means at 4 weeks pregnant your baby may be at most 1mm long, which is quite small. Keep in mind however that as you continue your pregnancy your body and your baby will change and grow dramatically!

Changes in Your Growing Baby

During pregnancy week 4 your baby starts implanting into the lining of your uterus. The uterus will safely and securely house your baby for the remaining weeks of your pregnancy. Your baby will start resembling a tiny tadpole more than a ball of cells now. This week your baby's amniotic cavity starts to form. From this cavity the placenta will grow and nourish your baby throughout your pregnancy.

The placenta is vital to your baby's health and well being. The placenta is mainly comprised of vascular networks and blood that carry oxygen and vital nutrients to your baby. During this time your baby's vital organs begin to take shape. Because of this from here on out your baby undergoes a critical period in his development. It is more important than ever from here on that you avoid exposing your body or your baby to harmful substances that can damage your baby.
Many substances are harmful for babies and can cause fetal malformations or deformities. Common substances that are known to be harmful include tobacco and alcohol. Substance abuse of any kind is contraindicated during pregnancy. If you have problems with any of these substances you should consult with your healthcare provider. Together the two of you can work out a plan of action for ensuring the health and safety of your baby during your pregnancy. Fortunately there are many support groups that support recovering addicts during their pregnancy. Remember it is vital to your health and the health of your unborn baby that you are open and honest with your healthcare practitioner about your lifestyle habits.

Your Body's Development

By 4 weeks pregnant you should be anxiously hoping that Aunt Flo will skip you buy this month. For many women the first sign they are pregnant is a missed period. If you miss your period there is a good chance you may be pregnant!

During the early weeks of your pregnancy before the placenta has time to fully form, the corpus luteum produces progesterone to help support the pregnancy. By roughly pregnancy week 12 however the placenta takes over this function and produces the progesterone your body needs to support your growing baby.

Some women have low progesterone levels. This may compromise a pregnancy and is sometimes the cause of repeat miscarriages. If you suspect you have low progesterone consult with your doctor. Fortunately there are a number of safe and effective treatments to overcome this problem!

Changes in Your Body

You might start feeling a little bit pregnant now. The most common symptom women experience this early in pregnancy (aside from a missed period) is increasing fatigue. That's no surprise given the work your body is performing to create a new life! Other women feel some mild abdominal cramping in early pregnancy while some report increasing breast tenderness.

By 4 weeks pregnant you should be able to take a home pregnancy test. You should call your healthcare provider as soon as you get a positive result to schedule your first prenatal visit. Most healthcare providers won't see patients until they are eight to ten weeks pregnant (unless they are in a high risk category) but you may need to schedule your appointment a few weeks in advance. Your doctor can also prescribe prenatal vitamins for you and ensure you are taking important steps to protect your health and that of your babies during your early pregnancy weeks.

Signs of Pregnancy

Before you miss your period, you'll want to be on the lookout for any signs that you could be pregnant. Some symptoms might show up this early, while others won't start until a week or two later. Here are a few signs of pregnancy you'll want to pay attention to:

Nausea or vomiting - This is called morning sickness, and it often doesn't hit until about four weeks after you conceive. However, some women can feel nauseous sooner.

Abdominal bloating - In early pregnancy, you may experience abdominal bloating. This sensation is similar to what you might have noticed prior to your regular menstrual period. Abdominal bloating is due to hormonal changes in your expectant body.

Fatigue - It's common for women to experience fatigue. You may feel super exhausted all of a sudden. Experts aren't quite sure what causes this early sign of pregnancy, but the rising levels of the hormone, progesterone, may play a role.

Swollen, Tender Breasts - Some women notice sensitive, tender, and swollen breasts as a result of the elevated hormones. Your swollen, tender breasts will decrease in discomfort once you pass the second trimester.

Video: What to Expect from the 4th Week of Pregnancy



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