Each month of pregnancy brings visible changes to both the growing baby and your body. From a cluster of cells smaller than a poppy seed to a full-term newborn the size of a watermelon, the transformation happens in distinct stages. Here’s what to expect month by month.
Month 1 (Weeks 1 Through 4)
Most of month one passes before you even know you’re pregnant. After fertilization, the embryo implants into the uterine wall and begins forming the very first structures: the neural tube, which will become the brain and spinal cord, plus the earliest building blocks for the head, eyes, and mouth. By the end of week 4, the embryo is about the size of a poppy seed.
Your body may not look any different yet, but hormonal shifts are already underway. A hormone called hCG starts rising rapidly after implantation, and it’s the substance that triggers a positive pregnancy test. You might notice extreme tiredness, tender breasts, or mild nausea even this early. Some people experience light spotting. No extra calories are needed during this stage.
Month 2 (Weeks 5 Through 8)
This is when things move fast. The cells that form the heart begin clustering around weeks 5 to 6 and start pulsing. Tiny buds that will become arms and legs appear around week 6. By the end of week 8, most of the embryo’s organs and major systems have taken shape. The baby grows from the size of a sesame seed at week 5 to a raspberry by week 8.
Morning sickness often peaks during this stretch, driven by hCG levels that climb steeply through weeks 8 to 12. You may also notice food cravings or strong aversions, mood swings, frequent urination, and constipation. Your breasts may feel noticeably swollen. Despite all these internal changes, most people aren’t visibly showing yet.
Month 3 (Weeks 9 Through 12)
The embryo officially becomes a fetus at week 9. Muscles are forming, and the body starts looking more recognizably human, though the head still makes up about half of its total length. By week 10, arms, hands, fingers, feet, and toes are fully formed with no more webbing between the digits. Fingernails and toenails start developing, and external ears take shape. A healthcare provider can often detect the heartbeat with a Doppler ultrasound around week 9. By week 12, the baby is about the size of a lime.
For you, month 3 is often the tail end of first-trimester symptoms. Fatigue and nausea typically begin easing as hCG levels peak and then decline. The placenta takes over hormone production around week 10, shifting from hCG dominance to higher levels of progesterone and estrogen for the rest of pregnancy. Genetic screening through a blood test is available during the first trimester for those who want it.
Month 4 (Weeks 13 Through 16)
Welcome to the second trimester, which many people call the most comfortable stretch. The baby is growing quickly, going from plum-sized at week 13 to about the size of an avocado by week 16. Facial features are becoming more defined, and the baby can start making small movements, though you probably won’t feel them yet.
Your abdomen begins expanding visibly. The “bump” often becomes noticeable to others for the first time around now. You may start to feel more energetic as early pregnancy symptoms fade. New changes can include body aches in the back, abdomen, or thighs. Some people notice a dark line forming on the skin from the belly button down to the pubic hairline, and the skin around the nipples may darken. Steady weight gain becomes more important from here on, with a goal of roughly 1 pound per week. An extra 300 calories a day is generally enough to support that.
Month 5 (Weeks 17 Through 20)
This is a milestone month. Many people feel the baby’s first movements, often described as flutters or bubbles, somewhere between weeks 18 and 20. The baby goes from the size of a turnip to about the length of a banana. An anatomy ultrasound, typically scheduled between weeks 18 and 22, gives you the first detailed look at the baby’s organs, limbs, and (if you want to know) sex.
Stretch marks may start appearing on your abdomen, breasts, thighs, or buttocks. Some people develop patches of darker skin on the cheeks, forehead, or nose, sometimes called the “mask of pregnancy.” Swelling in the ankles, fingers, or face can begin during this period as well. You might also notice numbness or tingling in your hands, similar to carpal tunnel syndrome, caused by fluid retention pressing on nerves.
Month 6 (Weeks 21 Through 24)
The baby’s senses are developing rapidly. By the end of this month, the baby is about as long as an ear of corn. The lungs are forming but are not yet mature enough to function outside the womb. Babies born at the very end of month 6 (around 24 to 25 weeks) can survive with intensive medical care, but the odds improve dramatically with each additional week of development.
A glucose screening test is standard between weeks 24 and 28 to check for gestational diabetes. Your belly is clearly rounded now, and the baby’s movements are strong enough that others can feel them through your skin. Itching on the abdomen is common as the skin stretches. Sudden or extreme swelling, especially in the face or hands, is worth reporting to your provider promptly.
Month 7 (Weeks 25 Through 28)
The baby is packing on weight and building fat stores that will help regulate body temperature after birth. Brain growth accelerates. By week 28, the baby is roughly the size of a large eggplant. The eyes can open and close, and the baby responds to light and sound.
You may start to feel mild, irregular tightening sensations in your uterus. These are Braxton Hicks contractions, essentially practice contractions that don’t signal labor. Heartburn and shortness of breath can intensify as the uterus pushes higher against your diaphragm. Bathroom trips become more frequent again as the baby’s weight presses on your bladder.
Month 8 (Weeks 29 Through 32)
The baby continues gaining weight rapidly, going from the size of a butternut squash to roughly the size of a papaya. The lungs are maturing but still need more time. The baby’s movements may feel different now, less like kicks and more like rolls and shifts, because there’s less room to maneuver.
Your body is working hard. Shortness of breath is common. Hemorrhoids can develop from the increased pressure in the pelvic area. Your breasts may start leaking a thin, yellowish fluid called colostrum, which is early milk. Sleep often becomes difficult, both from physical discomfort and from the need to urinate frequently during the night. Your belly button may pop outward.
Month 9 (Weeks 33 Through 36)
The baby is almost fully developed and spends this month adding the final layers of body fat. Size comparisons range from a pineapple at week 33 to a head of romaine lettuce by week 36. The baby may “drop” lower into your pelvis, a shift called lightening. When this happens, you might notice your belly looks different and breathing feels a bit easier, but pelvic pressure increases.
Your cervix begins softening and thinning in preparation for labor. Before labor starts, the cervix is typically 3.5 to 4 centimeters long. It needs to thin completely (a process called effacement) and open to 10 centimeters before a vaginal delivery. A thick mucus plug that has sealed the cervix throughout pregnancy may start to loosen and appear as increased vaginal discharge.
Month 10 (Weeks 37 Through 40)
Pregnancy is counted as 40 weeks, which means it stretches into a tenth calendar month. The baby is now full-term and roughly the size of a watermelon, typically weighing between 6 and 9 pounds. Organ systems are mature, and the baby is simply waiting for labor to begin.
For someone starting pregnancy at a healthy weight, total weight gain by this point is typically 25 to 35 pounds. Real contractions differ from the Braxton Hicks variety: they come at regular intervals, get closer together over time, and don’t ease up when you change positions. Other signs that labor is approaching include the baby dropping lower into the pelvis (if it hasn’t already), a noticeable increase in vaginal discharge, and contractions that gradually grow stronger and more frequent.
How Weight Gain Adds Up
Recommended total weight gain depends on your pre-pregnancy BMI. For a single pregnancy, the general targets are 28 to 40 pounds if you were underweight, 25 to 35 pounds at a healthy weight, 15 to 25 pounds if overweight, and 11 to 20 pounds if obese. For twins, the ranges are higher across every category. Most of the gain happens in the second and third trimesters, with little expected in the first 13 weeks. That extra 300 calories per day in the second and third trimesters is surprisingly modest: roughly a banana with peanut butter and a glass of milk.