You’re 5 weeks pregnant and you have officially missed a period! And if your pregnancy test wasn’t positive last week, you now have enough human chorionic gonadotropin (hCG) in your system to register a strong positive on a urine test. Mixed with the dizzy euphoria of finding out that you’re pregnant, you likely have lots of questions about what’s going on inside your body in week 5 of your pregnancy. Let’s jump on in!
Estimated reading time: 8 minutes
Updated July 18, 2021
Table of contents
- Baby’s Development in Week 5 of Pregnancy
- Week 5 Pregnancy Symptoms
- How is the Due Date Calculated?
- Week 5 Pregnancy Tip: Focus on Folic Acid
- Announcing Your Pregnancy
Baby’s Development in Week 5 of Pregnancy
At 5 weeks pregnant — just 3 weeks from conception — your baby is changing rapidly but hasn’t grown much in length from week 4. Baby now measures about 1.25mm, or .05 inches long (1).
Although teeny-tiny, your baby is doing some pretty incredible things this week. For example:
- Baby’s beating heart is now visible on an ultrasound
- Eyes begin to appear — they look like shallow grooves on either side of the brain
- Baby’s skeleton is starting to form
- Arm and leg buds are visible
- Brain has differentiated into 5 different areas
Week 5 Pregnancy Symptoms
There are a lot of changes going on inside your body, although you likely won’t be aware of most of them. Other symptoms that we discussed last week will come along soon, but the biggest symptom you’ll notice this week is a missed period.
It’s time for a quick biology lesson! Each month, your body thickens up the lining of your uterus, a blood and nutrient-rich layer known as the endometrium. If you don’t get pregnant, this layer sloughs off and your period begins.
But, you ARE pregnant! By now, in week 5 of your pregnancy, your fertilized egg has traveled from the fallopian tubes into the uterus where it implanted in the endometrium for nourishment. (This implantation sometimes causes a bit of spotting. Learn about Implantation Bleeding in Week 4 Pregnancy.) Implantation triggered your body to start producing human chorionic gonadotropin (hCG), which leads to a whole complex dance of hormones.
How it All Comes Together
In addition to tipping off a positive urine pregnancy test, hCG signals your ovaries to produce more estrogen and progesterone. (It’s also responsible for the morning sickness you’re likely to start feeling soon :/) Estrogen and progesterone tell your body NOT to have a period, but instead to start growing the placenta. (Progesterone also turns up your internal heat, leading to those uncomfortable night sweats.) Once it’s fully developed, the placenta will become a life-sustaining organ for your baby, delivering all of the oxygen, nutrients, and hormones that your baby needs to develop. (Learn more about the amazing placenta in our Week 12 Pregnancy article.) The umbilical cord grows out of the placenta, forming the connection between you and your baby (2,4).
How is the Due Date Calculated?
Last Menstrual Period
The average length of human gestation is around 280 days, or about 40 weeks, from the first day of your last menstrual period (LMP). The due date is calculated by simply taking the first day of your LMP and adding 280 days to it.
For instance, if your LMP was January 1st, the calculation would go as follows:
January 1 + 40 weeks = Estimated Due Date of October 8th
But what if you can’t remember your LMP but you know for sure when you ovulated? (Some women track their ovulation when trying to conceive.) There’s pretty strong evidence that conception usually occurs within 24 hours after ovulation, so the day of ovulation is often used to mark the beginning of a pregnancy. The average time from ovulation to birth is 268 days (38 weeks, 2 days). So, if necessary, you can calculate your estimated due date by adding 268 days to the day that you ovulated.
Due Date is Just an Estimate
Remember that the due date is merely an estimate and certainly not a prediction of the actual day your baby will be born. Studies have shown that only 4% of women will deliver at 280 days, and still, only 70% will deliver within 10 days of the estimated due date. This holds true even when the date is estimated by ultrasound, which is considered to be more accurate (3). Plan to deliver sometime within 2 weeks before or after your estimated due date.
Week 5 Pregnancy Tip: Focus on Folic Acid
You’ve probably heard about the recommendation to take folic acid — also called vitamin B9 or folate — for at least 1 year before conception. But if you haven’t jumped on the folic acid bandwagon yet, the time to begin is now!
Why Do You Need Folic Acid?
Baby’s neural tube, which will become the brain and spinal cord, forms very early in his or her development. It starts as a flat ribbon, and by the end of the first month, it is a tube. If the tube doesn’t close correctly, it can cause a neural tube defect like spina bifida or anencephaly. In the United States, this type of birth defect happens in about 3,000 pregnancies each year (5). But studies have shown that taking folic acid before pregnancy and in early pregnancy significantly reduces the risk of neural tube defects.
How Much Do You Need?
Before pregnancy and during the first 12 weeks of pregnancy, the recommendation is to take 400 micrograms of folic acid daily. In fact, (this might be helpful to remember when you’re not expecting) the CDC recommends that all women of reproductive age get 400 mcg of folic acid every day, because about half of U.S. pregnancies are unplanned (6). But know that at least during your pregnancy, you should make sure that this important vitamin makes it into your daily plans.
How to Get Folic Acid
In addition to vitamin supplementation, folic acid is also found in many of the foods you’re already eating. It’s added as a supplement to most fortified breads, cereals, and pastas. It also occurs naturally in foods such as:
- beans (like pinto beans, black beans, and lentils)
- citrus fruits and juices
- egg yolks
- green beans
- leafy green vegetables
Still, it’s difficult to get the recommended amount of folic acid from a healthy diet alone. For this reason, continue to take a daily vitamin supplement containing folic acid throughout your pregnancy (1,3).
Announcing Your Pregnancy
Telling others about your pregnancy is something you don’t have to do for quite a long time if that’s your preference. You have months before your changing shape gives you away. Still, when people learn that they’re expecting, they often think right away about who to tell and when. The great news is that there’s no wrong answer. Some people like to wait until they reach the end of the first trimester, when the risk of miscarriage drops, because they feel like they wouldn’t want to have to go through telling people about a loss. Other people tell their close family and friends as soon as they find out, knowing that most pregnancies don’t end in a loss, and thinking that if the worst were to happen, their loved ones could be part of the support they’d need.
The bottom line is that there’s no right or wrong way to do things. Who to tell, when to tell, and how to tell are all a matter of what feels right to you.
Come back next week to learn what’s happening with your body and your baby in week 6! And if you’re ready to jump in and learn all about what to expect in the first trimester, check out First Trimester Pregnancy & Symptoms: The Ultimate Guide.
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- Glade, B.C., Schuler, J. (2011). Your Pregnancy Week by Week, 7th edition. First Da Capo Press.
- Ladewig, P.A., London, M.L., Davidson, M.R. (2006). Contemporary Maternal-Newborn Nursing Care, 6th edition. Pearson Prentice Hall. Upper Saddle River, NJ.
- Jukic, A. M., Baird, D. D., Weinberg, C. R., McConnaughey, D. R., & Wilcox, A. J. (2013). Length of human pregnancy and contributors to its natural variation. Human Reproduction (Oxford, England), 28(10), 2848–2855. http://doi.org/10.1093/humrep/det297
- The American College of Obstetricians and Gynecologists. (2010). Your Pregnancy and Childbirth Month to Month, 5th edition.
- Neural tube defects. March of Dimes. (n.d.). https://www.marchofdimes.org/complications/neural-tube-defects.aspx.
- Centers for Disease Control and Prevention. (2021, April 19). Folic Acid. Centers for Disease Control and Prevention. https://www.cdc.gov/ncbddd/folicacid/about.html.