At 4 weeks pregnant, the blastocyst (or ball of cells that will become your baby) is working furiously to implant itself in the uterine lining. This will ensure a safe home for your little one over the next nine months. The amniotic cavity and placenta are also forming during pregnancy week four. Fetal development by and large is still in the earliest stages at this point.
Your baby is incredibly miniscule, about .014 to .04 inches long. That is roughly the equivalent to 1/2 to 1mm long, which is comparable in size to a mustard seed. Over the next few weeks, your baby will slowly start resembling a small tadpole with eyes, rather than an egg. That is quite an accomplishment for your little one!
As you continue to grow and expand, the placenta will help nourish and support your baby during the nine months of pregnancy. It consists of vascular networks and blood from your body that helps transport oxygen and nutrients to the fetus. There are several different layers of cells forming in your body, which will eventually develop into your baby's organs and other body parts. Other layers will form baby's nervous system including his/her brain.
This early stage of pregnancy is often noted as the beginning of the embryonic period.
By the end of 4 weeks pregnant you would normally expect your period to arrive. If it does not, there is a good chance you might be pregnant!
During the early weeks of pregnancy before the placenta is fully formed, an area of your ovary forms what is called the corpus luteum. This generally occurs at the site where your egg is released from the follicle. The corpus luteum is believed to produce progesterone during the early weeks of pregnancy. By about 12 weeks, the placenta actually starts producing the majority of progesterone your body needs to carry a pregnancy.
You might actually start realizing some changes at 4 weeks pregnant. Some women start to feel a little bit tired during pregnancy at 4 weeks, which is not a surprise given the remarkable work your body is performing to support your new baby!
At 4 weeks pregnant, your baby is working hard and furious to embed herself into the lining of your uterus. This process is called implantation, and it can cause early symptoms to emerge – such as cramping and light spotting.
Cramping at 4 weeks pregnant is normal, and it's a sign of implantation. Some women describe this cramping akin to light menstrual cramps. Mild cramping at 4 weeks pregnant isn't anything to worry about. However, if cramps are extremely painful, or if they are accompanied with heavy vaginal bleeding, chills, or fever, contact your doctor or healthcare provider right away.
Light spotting can be normal at 4 weeks pregnant, and it's due to implantation bleeding. Spotting is typically pink or light brown. It should never be heavy, or bright red like your regular menstrual period.
In addition to the signs of implantation, you may start to experience a few early pregnancy symptoms at 4 weeks pregnant.
Nausea or vomiting (aka morning sickness) can start as early as 4 weeks pregnant in some women, but it's more common at 6 weeks. You may find that you're feeling slightly queasy this week, and the smells of certain foods might make you gag. Your nausea is only going to get worse as the weeks progress. Morning sickness usually doesn't go away until the second trimester.
Tender, swollen breasts are an uncomfortable pregnancy symptom to expect at 4 weeks pregnant. Even before you miss your period, your breasts may swell (even get larger) and be sore to touch. Many pregnant women describe the sensation as similar to how your breasts feel right before your period – only it's 10 times worse.
Frequent urination is one of the early symptoms of pregnancy, and it can strike as early as 4 weeks pregnant. After you conceive a baby, heightened hormones can cause more blood to flow through the kidneys, causing your bladder to fill up more often. When you realize that you have 50 percent more blood pumping through your pregnant body, this is a lot of extra fluid that's processed through the kidneys. It's no wonder that pregnant women have to run to the bathroom so often!
Your weight gain at 4 weeks pregnant is under a pound. You shouldn’t expect a hefty weight gain yet, since you’re barely pregnant. You have another 36 weeks to look forward to. Not to worry - you will steadily pack on the pounds as your pregnancy week by week progresses.
By the time you reach 40 weeks pregnant, you will have gained between 25 and 35 pounds if you’re the average-sized woman. This is the recommended pregnancy weight gain, but some women will gain more and others less.
Many women will be able to find out if they are expecting at 4 weeks pregnant. A home pregnancy test is sufficient for determining whether or not you are pregnant. If you take a test and find that you are pregnant, you should call your healthcare provider to set up your first prenatal visit. Chances are they won't want to see you for a few more weeks, but it is important nonetheless to schedule your visits. Your healthcare provider can also prescribe a prenatal vitamin if you aren't already taking one.
Some women are disappointed to find that their pregnancy test comes back negative. Give it some time. Some women don't produce enough pregnancy hormones right away for a standard test to detect a pregnancy.
How long it takes to get pregnant depends on a number of factors. Some women will try for several months before they actually get pregnant. Most practitioners will not consider infertility a problem unless you have been trying to get pregnant for more than a year with no results. At that time, your healthcare provider might suggest some special tests to determine what obstacles you might be facing.
Remember that stress is a big hindrance to pregnancy. Some women find that as soon as they stop trying, they actually get pregnant. It may sound strange, but the body is a very complex machine, and small things including stress can influence your body's ability to function normally. If you find yourself unusually stressed, consider some yoga or other meditative practices to help you remain calm and relaxed.
At pregnancy 4 weeks, if you take a home pregnancy test too early, it may give you false hopes. Sometimes, a woman can get a positive home pregnancy test, but then she has her period. This false positive is the result of a chemical pregnancy - a very early miscarriage in which the fertilized egg doesn’t implant in the lining of your uterus.
Although experiencing a chemical pregnancy is heartbreaking, this is a normal occurrence, and there’s nothing you did to lead to this early pregnancy loss. A majority of the time, the miscarriage is due to a chromosomal abnormality in the fertilized egg. Experts believe that chemical pregnancies account for 50 to 75 percent of all miscarriages.
The early weeks of pregnancy are considered a critical time of development. Any exposure to harmful substances during pregnancy week 4 or later in the first trimester is most likely to cause damage to or harm your developing fetus. It is extremely important that you do everything possible to try to avoid exposure to any potential pollutants or toxins during this time. You should inform your healthcare practitioner if you are exposed to any potentially hazardous substances that might affect your baby's development.
Remember that the most common substances implicated in fetal deformities or malformations are common toxins such as alcohol and tobacco. Substance abuse of any type can also be harmful to an unborn baby. If you have an addiction, you should talk with your healthcare provider immediately so they can help you determine the best way to proceed. Your healthcare provider will likely direct you to some support groups so that you can change your habits during this highly important time.
Did you know that environmental pollutants are just as harmful as other toxins you might ingest during pregnancy? It is important that you are aware of any environmental toxins and pollutants that may harm your fetus during pregnancy. Some of the more common pollutants that can affect fetal development include: lead, mercury, pesticides and PCBs. PCBs are mixtures of chemical compounds. Some women are exposed to certain PCBs at work. At 4 weeks pregnant, if you work in an environment where a variety of chemicals are used, you might check in with your healthcare provider to ensure that your work environment is safe.
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By the end of 4 weeks pregnant you would normally expect your period to arrive. If it does not, there is a good chance you might be 
Many women will be able to find out if they are expecting at 4 weeks pregnant. A home 
The early weeks of pregnancy are considered a critical time of development. Any exposure to harmful substances during pregnancy week 4 or later in the first trimester is most likely to cause damage to or harm your developing fetus. It is extremely important that you do everything possible to try to avoid exposure to any potential pollutants or toxins during this time. You should inform your healthcare practitioner if you are exposed to any potentially hazardous substances that might affect your baby's development. 