Healthy Pregnancy: Your First Trimester Guide

The First Trimester

This pregnancy guide explains your baby's growth, as well as the aches, weight gain, morning sickness and other changes during the first trimester.

1 / 10 The First Trimester

Pregnancy can be a thrilling—and scary—time. That’s why we turned to Rabiya Suleman, OB/GYN, MD, at Specialists in Women’s Care in Lansing, KS to explain your pregnancy week-by-week. With her help we’ll guide you through the next 40 weeks, discussing 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. Click through to find out what to expect during your first trimester. 

Medically reviewed in June 2019.

Fertilization to 5 weeks

2 / 10 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,” says Dr. Suleman. 
6 Weeks – Baby’s Size: Pomegranate Seed

3 / 10 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.

What the doc says: “Morning sickness can occur anytime, anywhere, from once or twice a day to 7 to 10 times a day,” says Dr. Suleman.  But try not to worry—symptoms usually ease up by the end of the first trimester.  

7 Weeks – Baby’s Size: Small blueberry

4 / 10 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 more.

What the doc says: 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,” says Suleman. 

8 Weeks – Baby’s Size: Raspberry

5 / 10 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.

What the doc says: “I actually encourage my patients to get as much rest as they can in the first trimester because your body is doing a lot of work on the inside that you cannot see on the outside,” says Suleman. 

9 Weeks – Baby's Size: Grape

6 / 10 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.

What the doc says: “The first prenatal visit should occur between seven and nine weeks,” says Suleman, “You’ll have an exam, blood work and counseling on what to expect during pregnancy.”


10 Weeks – Baby’s Size: Kumquat

7 / 10 10 Weeks – Baby’s Size: Kumquat

Your Baby: The kidneys, intestines, brain and liver are 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.

What the doc says: “During your pregnancy, you’ll want to be immunized for whooping cough during the third trimester, and the flu during flu season,” says Suleman.  

11 Weeks – Baby’s Size: Lime

8 / 10 11 Weeks – Baby’s Size: Lime

Your baby: His bones are hardening, and his hands can close into fists. Don’t be surprised if you feel him hiccupping as his diaphragm forms.

You: You may feel some discomfort from constipation and heartburn.

What the doc says: “The sphincter between the stomach and the esophagus loosens during pregnancy, which causes heartburn,” says Suleman. “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

9 / 10 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 abdomen, 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.

What the doc says: Good news! Nausea should be subsiding, and you may not feel as sluggish anymore, says Suleman.  

13 Weeks – Baby’s Size: Peach

10 / 10 13 Weeks – Baby’s Size: Peach

Your Baby: He’s about 3-inches long, 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 more calories/day to nourish your growing baby.

What the doc says: Don’t worry if you’re not seeing a bump yet. “Some women won’t show until 20 to 25 weeks,” says Dr. Suleman. “[That] doesn’t mean your uterus isn’t growing appropriately.” Your doctor will measure your uterus to see if it’s the size it should be.

Continue to the Second Trimester Guide

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