In week 4 of pregnancy, your body is beginning to form the placenta and amniotic sac.
Symptoms like abdominal pressure and tender breasts may appear this week, and as the cluster of cells that will soon become your baby burrows into your uterine lining, you may also spot some implantation bleeding. (But if you don't notice any symptoms at all yet, that's completely normal too.) If you’re 4 weeks pregnant, you're in month 1 of your pregnancy. Only 8 months to go! Still have questions? Here's some more information on how weeks, months and trimesters are broken down in pregnancy. Despite its extremely tiny size — no longer than 1 millimeter and no bigger than a poppy seed (think about that as you eat your morning bagel) — your little embryo is busy setting up house. You can keep track of your baby's growth each week with the What to Expect app. While you may have just started to wonder whether you're pregnant, your soon-to-be baby has already found its home: The blastocyst has completed its journey from your fallopian tube to your uterus. Once there, it burrows into your uterine lining and implants — making that unbreakable connection to you that'll last the next eight months (and a lifetime after that). As soon as that little ball of cells is settled in your uterus, it will undergo the great divide, splitting into two groups. Half of what's now called the embryo will become your son or daughter, while the other half forms the placenta, your baby's lifeline — which channels nutrients and carries waste away until delivery. While the amniotic sac (also called the bag of waters) forms around it, so does the yolk sac, which will later be incorporated into your baby's developing digestive tract. The embryo now has three distinct layers of cells that will grow into specialized parts of your baby's body. The inner layer, known as the endoderm, will develop into your baby's digestive system, liver and lungs. The middle layer, called the mesoderm, will soon be your baby's heart, sex organs, bones, kidneys and muscles. And the outer layer, or ectoderm, will eventually form your baby's nervous system, hair, eyes and outer layer of skin. Just a week after fertilization, baby-making is still in its infancy, so to speak. At 4 weeks pregnant, your body is gearing up, big-time — transforming quickly into a baby-growing haven that will house your little miracle for the next nine months or so. Chances are you're oblivious to all the hubbub. While some women experience those pesky, PMS-like early pregnancy symptoms, including mood swings, bloating and cramping, others don't feel a thing. Whatever you're feeling or not feeling, it may be too early to see a reliable result on your pregnancy test. Though you may not feel pregnant quite yet, here's what's going on behind the scenes. The fertilized egg and your uterus are making contact this week in a process called implantation, as the blastocyst you'll one day call your baby begins to attach itself to the uterine lining. Up to 25 percent of the time, implantation bleeding will occur as that bundle of cells burrows its way into the uterine wall. Implantation bleeding, which is usually very scant and either light pink, light red or light brown, occurs earlier than your expected period. Don't mistake it for your period and don't worry about the bleeding — it's not a sign that something is wrong. You might feel a little pressure in your abdomen (nothing to worry about!) and your breasts may feel a little tender and become even bigger (but get ready for more growth spurts!). Within six to 12 days after fertilization, the egg starts to release hCG, or human chorionic gonadotropin — the pregnancy hormone that will very soon turn that line on your pregnancy test pink or blue and your world upside down. HCG alerts the corpus luteum (the once-follicle this egg was released from) that it needs to stick around and produce progesterone and estrogen to nourish the pregnancy until the placenta takes over about eight weeks from now. If you haven’t started taking a prenatal vitamin yet, now’s the time. (And no, a standard multi won’t do.) Prenatals contain vitamins and minerals that are essential for your growing baby. For example, folic acid (aka folate) — which is found naturally in whole grains, green leafy vegetables, beans, bananas, broccoli and milk, and added via fortification to breads and cereals — is not only critical for neural tube development early in pregnancy but also for the development of your baby's brain during all nine months. The best prenatal for you is the one that you can actually tolerate — which, for some people, may be a chewable or liquid option, or a softgel coated in gelatin. Whichever prenatal you choose, make sure it hits, or comes close to, the recommended intake of folic acid, iron (if you can tolerate it), calcium, vitamin D, choline, omega-3 fatty acids, B vitamins and vitamin C. Think you need a Ph.D. in quantum physics to figure out your due date? Doing the math is actually a lot easier than you think — even if you slept through high school algebra. Your estimated due date is 40 weeks from the first day of your last period. Here's the slightly confusing part: If you do give birth on that day, your baby will have clocked in only 38 weeks in utero, not 40. That's because the pregnancy countdown begins two weeks before your baby is even conceived — making you about four weeks pregnant before you see a positive pregnancy test. Regardless, you shouldn't plan your schedule around your estimated due date. After all, it is just an estimate. Most babies are born between 38 and 42 weeks, and babies of first-time moms are more likely to arrive on the later side. Only a handful of babies actually make their debuts right on schedule. If your pregnant test is showing a barely visible, faint line — one that looks more like a smudge of chalk — it usually means that implantation has occurred. Still, you’ll want to take the test again in a few days or so to make sure the line has become thicker and darker, which means your pregnancy is progressing. If you see a faint line on your pregnancy test but get your period later on, that means you were only briefly pregnant. In this case, you may have experienced a very early (and common) pregnancy loss called a chemical pregnancy. As upsetting as this may be, it won’t impact your ability to get pregnant in the future. Priority number one is having a healthy baby. But it’s not uncommon to have your heart set on having a boy or girl, especially if you’ve already had a baby of the opposite sex. Unless you’re getting an assist from science — in the form of preimplantation genetic diagnosis (which is used along with IVF) or sperm sorting — there’s no real way to choose the sex of your baby. That said, some couples swear by the Shettles Method, which theorizes that having sex as close to ovulation as possible can net you a baby boy (Y-sperm are supposedly speedier); having sex two to three days before ovulation can yield a baby girl (X-sperm are supposedly slower but more resilient). In general, healthy couples have a 20 to 25 percent chance of getting pregnant during each month’s cycle. The catch: That assumes you’re having sex “regularly” — two to three times a week — and without contraception. About 85 percent of couples who are trying to conceive will get pregnant within a year. Once sperm meets egg, you can expect the process to go fairly quickly — it’ll take about two to three weeks for the fertilized egg to travel to the uterus and implant on the uterine wall, resulting in a pregnancy. Once the fertilized egg travels down the fallopian tubes, it will implant into the wall of the uterus — a process aptly known as implantation. Many women don’t experience any symptoms of implantation, but some will feel abdominal cramps and light bleeding. Whether you feel anything or not, implantation marks the beginning of your pregnancy. It won’t be long now! Drugstore pregnancy tests aren’t always cheap, but they are up to 99 percent accurate. Homemade pregnancy tests, on the other hand — while popular with bloggers and on YouTube — aren’t reliable at all (though they can be entertaining to try!). The thinking goes that by combining your urine with salt, sugar, toothpaste, or even bleach, you can detect the presence of the pregnancy hormone human chorionic gonadotropin (hCG). But there’s no evidence that these tests can yield an accurate result, and no major medical organization recommends using them. Still, if you want to try one for fun, have at it (as long as you go in knowing they're just for laughs).Your Baby at Week 4
At a Glance
4 weeks pregnant is how many months?
How big is my baby at 4 weeks?
Placenta and embryo begin forming
Development of the embryo and amniotic sac
Your Body at Week 4
No symptoms yet?
The egg implants
Pregnancy hormones will soon make an appearance
Pregnancy Symptoms Week 4
Tips for You This Week
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