Pregnancy can be a thrilling—and scary—time. That’s why we created this guide to explain your pregnancy week-by-week. We’ll discuss a baby’s growth and development, as well as what’s in store for you, including everything from morning sickness to the first flutters of movement. Here’s what to expect during your first trimester.
Fertilization to 5 weeks
Before your baby becomes the child you’ll love on for the rest of your life, he starts out as a tiny ball of cells that will multiply like crazy. Within the first week, he will make a home in your uterus, and estrogen and progesterone will increase to protect your uterus and stimulate placenta growth. During this time you may not even realize you’re pregnant. If you’re trying to conceive, you should take a pregnancy test if you experience any changes in your period, no matter how subtle.
6 weeks – baby’s size: pomegranate seed
Your baby: Her nose, mouth and ears are forming, as well as her digestive and respiratory systems. Tiny buds appear where her arms and legs will grow, and her heart has begun to beat.
You: Morning sickness, nausea, fatigue and mood swings all may occur. Morning sickness can occur anytime, anywhere, from once or twice a day to seven to 10 times a day. But try not to worry—symptoms usually ease up by the end of the first trimester.
7 weeks – baby’s size: small blueberry
Your baby: His umbilical cord has formed, providing oxygen and nutrition. He’s developed hands, which look like tiny paddles.
You: Your uterus is about the size of a grapefruit this week, and you’re probably eating (and peeing!) now more than ever. Some spotting is normal during pregnancy. Brown blood is usually okay, but red blood may indicate active bleeding. Regardless of color, you’ll want to tell your provider about any spotting to make sure that everything is okay.
8 weeks – baby’s size: raspberry
Your baby: His major organs and external body parts are forming, and his heart is beating at a regular pace. His arms and legs are growing, and his little fingers and toes are taking shape.
You: Morning sickness and hormonal changes may make you feel sluggish. Your breasts may get fuller or heavier and feel sore. Get as much rest as you can, because your body is doing a lot of work on the inside that you cannot see on the outside.
9 weeks – baby's size: grape
Your baby: Your little pumpkin’s head is quite large compared to his body. His heart is dividing into four chambers, and tiny teeth are forming beneath the gums.
You: If you haven’t experienced mood swings yet, they’re probably in full force right now. The first prenatal visit should occur between seven and nine weeks. You’ll have an exam, blood work and counseling on what to expect during pregnancy.
10 weeks – baby’s size: kumquat
Your baby: The kidneys, intestines, brain and liver are now working together, and he’s swallowing fluid. His fingernails and toenails are forming, and he’s sprouting peach-fuzz hair on his skin.
You: Your OB/GYN will check your blood to find out if you’ve gotten certain immunizations, as well as determine your blood type and Rh factor. During your pregnancy, you’ll want to be immunized for whooping cough during the third trimester, and the flu during flu season.
11 weeks – baby’s size: lime
Your baby: His bones are hardening, and his hands can close into little fists. Don’t be surprised if you feel him hiccupping as his diaphragm forms.
You: You may feel some discomfort as constipation and heartburn kicks in around this time. The sphincter between the stomach and the esophagus loosens during pregnancy, which causes heartburn. You can reduce symptoms by eating small, frequent meals, taking walks after eating and avoiding triggers like acidic or spicy foods.
12 weeks – baby’s size: plum
Your baby: Reflexes have kicked in, so she can move her fingers, wiggle her toes and make sucking movements with her mouth. Her intestines are moving into her abdominal cavity, and her kidneys are moving urine into the bladder.
You: You’ve probably started gaining weight by now. That’s normal -- doctors recommend women who had a healthy weight before pregnancy gain around 25 to 35 pounds. Nausea should be subsiding, and you may not feel as sluggish anymore.
13 weeks – baby’s size: peach
Your baby: He’s about three inches long and weighs about an ounce, and his head is becoming more proportional to the rest of his body.
You: Make sure you’re taking prenatal vitamins, and eating about 300 extra calories a day to help nourish your growing baby. Don’t worry if you’re not seeing a bump yet. Some women won’t show until 20 to 25 weeks. On each visit, your doctor should measure your uterus to see if it’s the size it should be.