Your first trimester is from week 1 to week 12. Your pregnancy begins at conception even though your “due date” is calculated based on when you last got your period (about two weeks before conception).
The dating of your pregnancy can be confusing. Since your last period is pretty easy to mark on the calendar, that's used as the start of your pregnancy.
It may not seem like it, but your body is going through major changes! Your baby is going through the most rapid period of growth he or she will ever go through 🙂
Your baby is conceived when sperm meets egg. Only one sperm can enter the egg – it burrows down into the inner part of the egg, and all other sperm are sealed out.
The sperm head swells into a nucleus within the egg, and the egg forms its own nucleus. Each of these has 23 chromosomes that move closer together until they become one nucleus containing all of the information needed for your baby to begin.
Fertilization usually occurs in the Fallopian tubes. The fertilized egg, called a zygote, migrates from the fallopian tube to the uterus. The cells begin dividing before your newly conceived baby makes it to the uterus. Once it arrives, it burrows into the lining of the uterus. This is called implantation.
The embryo leaves its protective shell behind when it burrows into the uterine lining. The cells for baby and placenta have already separated. Your tiny ball of cells forms into a more human shape rapidly, but for now your baby is very small – smaller than a period on this page! The cells that make up your baby continue to divide rapidly over the coming week.
You may notice some light implantation spotting, but you probably won't know you're pregnant yet. Some women have pain around ovulation time: an indicator that pregnancy is possible.
Stop smoking, drinking or doing any illegal drugs. Use caution with over-the-counter drugs, caffeine, and herbal/alternative remedies. There are differing medical opinions on what's safe and what's not safe during pregnancy. The very best bet is probably just to stop everything. Have a healthy, natural pregnancy and avoid any unnatural or potentially harmful substances.
As your baby completes implantation, he or she is officially called an embryo! The amniotic sac begins to form, and a yolk sac that nourishes your baby early in your pregnancy also begins forming.
Your baby starts to take on a more formed shape, looking somewhat like a tadpole. Your baby is entering periods of vital development – avoid exposure to anything that might hurt your baby.
This rapid growth continues throughout the first trimester. Choose natural bath and body products and try and use natural products around the house. Limit your exposure to pollution or second-hand smoke. Also try to avoid paint fumes and fertilizers. Organ systems are forming rapidly and your baby is more susceptible to teratogens (substances harmful for fetal development).
Your baby's placenta is starting to develop. Your blood supply and your baby's are separated by a thin membrane of the placenta and all the nutrients he or she needs pass through it. Waste products pass from baby's side to your side and your body deals with them.
Hormones that tell your body you're pregnant begin circulating. Your body halts any ovulation preparations and begins to build the lining of the uterus. These hormones also protect the baby from being rejected by your body.
By the end of this week you may be feeling mild nausea or fatigue. Some women also report having a metallic taste in their mouth, and your breasts may become tender. If you've been charting your temperature, you'll be watching to see if your temperature drops or not (if it's high for 20 days, you're most likely pregnant!)
By the end of this week you may realize that your period is late. A home pregnancy test can confirm this. Your attention to your diet helps keep your baby happy and healthy during the first trimester, so take care of yourself while you wait on your first prenatal appointment! You may go into the office for a prenatal workup, which is a series of blood tests to assess your health at the beginning of pregnancy.
The baby has a head and a tail end with the forerunner of the brain and spinal cord developing. The chorionic villi, or the tissue that line the placenta, have finished forming. If you opt for a CVS test, these are the tissues used for the sample. The villi grow so that they end up dipped in “lakes” of your blood, though your blood and your baby's never actually mix.
This is how nutrients are transferred from your blood to your baby's. Late this week your baby will enter a critical period for heart development.
You'll miss your period this week and start suspecting pregnancy (if you haven't already)! Take a home pregnancy test or call your doctor or midwife. Your breasts may feel sore or tender – it is often a first sign of pregnancy. Fatigue and queasiness may continue or begin this week.
Things with strong tastes and smells can cause nausea. We don't know exactly what causes nausea or “morning sickness” – this could be how your baby's placenta ensures that nothing harmful is going to get to your baby – especially during the sensitive first trimester.
Your baby is developing so rapidly during the first trimester, so be very careful with what you eat and what you are exposed to. Great prenatal nutrition goes a long way towards keeping you and your baby healthy and safe from environmental risks.
Work on a good pregnancy diet focusing on fresh, natural foods. If nausea is already getting to you, “graze” on small, frequent meals. Click here for helpful hints on getting through these challenges.
The baby's brain and spinal cord start to form, along with bones that will protect them. The beginnings of the face are also present.
Most organs, along with blood, blood vessels, and a heart have started forming. Your baby's heart begins to beat around the 25th day after conception. The yolk sac is nourishing your baby this week, and the placenta continues to develop.
Your baby is also developing eyes and the earliest beginnings of ears. Your baby enters into a critical period for arm and leg development this week.
You might get a positive pregnancy test this week if you haven't already! It's a really exciting time for you and your baby. It's normal to experience mood swings or even have periods of crying – your body is being flooded with hormones!
You probably need to go to the bathroom more. Don't hold it; keeping your bladder empty is essential for keeping yourself healthy. It gets annoying to pee so frequently, but a clear bladder prevents infection.
Don't decrease your liquid intake either; shoot for 6-8 cups of water daily. This helps your body deal with wastes and eases the added stress on your liver. You can also sip on milk or broths.
Pregnancy discomforts are likely to be minor annoyances throughout your pregnancy, but you can look into natural ways of dealing with most of them.
The surface of your baby's skin is starting to develop. Sexual organs are developing, but they have not yet developed into testes or ovaries. Your baby's brain has divided into three main parts: the forebrain, the midbrain, and the hindbrain. The two hemispheres of your baby's brain are also visible this week. Your baby now measures 1/4 inch!
Your baby's body is undergoing vital development this week. His or her brain, body, and head are growing rapidly. A tiny mouth is forming on your little one, and within it is your baby's tongue.
Your baby doesn't need to take anything in through his or her mouth yet. The umbilical cord sends all the nutrients needed right to your baby. Your diet is important for your baby. It gives him or her the vital nutrients needed to work through such rapid development.
Folic acid has been shown to be very beneficial to your baby, and can provide protection from some birth defects. You can get folic acid through your diet. Include plenty of fresh fruits and vegetables. A high quality prenatal vitamin will also have folic acid in it to support your baby's rapid first trimester growth.
If you are having trouble with morning sickness or nausea, continue to eat small, frequent meals. If you get sick, eat again. Your baby needs to you to keep eating well. Choose foods that give a lot of nutrition in a small package. Bland foods like yogurts and nuts give a lot of protein and nutrients without a strong taste.
You may be able to get down fruit smoothies. Make your own with yogurt and fresh fruit (or fresh-frozen fruit) rather than buying store bought varieties or mixes, which contain unnatural additives. You can “sneak in” other supplements through smoothies as well, such as a powdered prenatal vitamin.
The baby's face, arms, and legs continue to develop. Fingers and toes begin to form this week, and baby has handprints and footprints! The baby's “tail” is nearly gone. The brain is in control of the body and directing the development of your baby. Your baby's pituitary gland is also forming this week.
Baby's skeleton is complete but still made of soft cartilage. Baby teeth are forming under your baby's gums. Your baby's intestines are forming within the umbilical cord. They will move into your baby's body once he or she is big enough to hold them.
You may be experiencing mood swings or apprehension, even if you were planning this pregnancy. It's normal to feel unsure about becoming a parent for the first time, or about becoming a parent again. Try journaling your feelings, or talking with someone you can trust.
You may feel sick and tired in the first trimester, which can make it even harder to deal with changing feelings. Be easy on yourself. Continue to eat well and get the rest that you need. Click here for more tips on surviving your first trimester.
Have you shared the news? Some women want to tell everyone as soon as they find out they are pregnant. Others want to wait until the end of the first trimester. As the first trimester closes, your risk of miscarriage decreases greatly. You can choose to tell people about your pregnancy as soon as you feel ready. If you want to spill the beans, go right ahead! If you want to wait, that's okay too. It's even okay if you don't tell anybody 😉 !
Baby is sensitive to touch this week! In the next week or so your baby develops either testes or ovaries, giving a physical indication of sex. It'll be many weeks before gender is discernible by ultrasound scan, however.
Your baby's limbs are becoming more proportional to the body and elbow and knee areas are starting to be discernible. Your baby's body will begin to straighten out some.
Your baby's heart has separated into four chambers by this week, which is a big accomplishment. The four-chambered heart allows for internal temperature regulation. Animals with only two chambers must rely on outside assistance (such as the sun) to regulate their temperature.
Your baby's brain isn't yet developed enough for temperature regulation, and even after he or she is born, you still need to help keep baby warm. But a four chambered heart means that it won't be long before your baby can effectively regulate his or her own temperature.
Did you know that being skin-to-skin with you regulates your baby's temperature, heart rate, breathing, and even blood glucose (blood sugar) levels? Being skin-to-skin (also called “kangaroo care”) after birth is one of the most important things you can do for your baby's health. Plan on a natural birth and lots of skin-to-skin time immediately postpartum (baby can be in just a diaper and both of you can be covered in a blanket to stay cozy!)
Kegel exercises strengthen your pelvic floor and pregnancy is a great time to get into the habit of doing them. They are simply an intentional contraction and relaxation of the pelvic floor muscles and help prepare those muscles for the birth of your baby. Focus not just on contracting the muscles, but also what it feels like to have them soft and relaxed 🙂
The retina of your baby's eye is fully pigmented this week. Your baby has fingers and a thumb, though they are webbed, and there are small grooves forming for toes. Your baby's external ears have been developing along with his or her eyelids and tongue! Your baby's head has a rounded look now.
This week your baby has the distinction of being called a fetus instead of an embryo. Within the next couple of weeks risks to your baby decrease somewhat. The risks of some birth defects and congenital malformations drop after this week. Your risk of miscarriage begins to drop dramatically and is very small by the end of the first trimester.
Your clothes may be starting to feel a little tight around your abdomen. Choose pants with a loose fit or an elastic waist (a rubber band can be useful for your jeans). Pick something comfortable that doesn't restrict your circulation.
You may be longing to be past the first trimester and looking forward to a “bump” that will allow you to wear maternity clothes. Your uterus is about the size of a tennis ball by the end of this week, though your baby is still very tiny.
Or you might still be feeling a lot of morning sickness and simply be wishing that you were farther along to be over it! Remember to eat small, frequent meals and foods that offer a lot “nutritional bang for their buck.”
Your baby is growing rapidly now. He or she was growing quickly before now, but a lot that growth was organs and body systems developing. Your baby's bones and muscles are now growing quickly and your baby begins to take on the proportions that he or she has as a newborn.
If your baby is a girl, her vagina is forming this week, and if your baby is a boy, his penis is forming (though ultrasound cannot tell sex in the first trimester.) Your baby's posture is more upright this week.
Keep taking care of yourself! Nausea could be fading… or you might still feel sick. Normal household tasks can make you feel ill. It's best for you and for your baby if you're careful about what you eat and about what you use around the house. Use natural and/or homemade cleaning products. They smell better, and they don't emit harmful fumes.
Start taking pictures of your belly every week. “Belly pics” are special now and after your baby is born. Most women remember their pregnancies fondly and like to look back at how their belly grew from the first trimester onwards.
Nails and hair are forming on your baby. Genitals are well formed and distinguish boys from girls. Your baby is starting to urinate to clear wastes. Your baby's pancreas, gall bladder, and thyroid are each going through major growth.
Parts essential to your baby's future digestive process are developing this week – the hard palate and the muscles in the walls of your baby's digestive tract.
Your baby's skin is very thin and translucent. If you could see your baby, you would be able to see all his or her veins and blood vessels running under the skin. Your baby is still tiny; he or she could fit in the palm of your hand! However, your baby has grown an amazing amount since the microscopic little being he or she was at conception!
Your body is processing your baby's wastes. As he or she excretes urine, it's filtered out of the amniotic fluid by the placenta. Your body then deals with it along with your own wastes.
Support your liver with good nutrition because it's doing double duty during pregnancy! Eat leafy greens, vitamin C rich foods, and yellow pigmented foods to help your liver get its work done. Protein is also very important, even in the first trimester.
Continue to graze if you're still feeling nauseous. Your appetite may be picking up as you move through the first trimester. Eat nutrient dense foods and don't worry about weight gain. Cut out junk foods if you feel the need to cut something out!
Some women don't “show” for a long time, and some show much earlier. Congratulations making it through the first trimester! On to the second trimester – often the favorite!