Four months pregnant corresponds to roughly weeks 14 through 17 of pregnancy, though sources vary slightly on where to draw the line. The confusion is understandable: pregnancy is tracked in 40 weeks, but 40 weeks divided by 9 months doesn’t produce neat, round numbers. Most providers consider weeks 16 to 18 the point where you’ve clearly started your fourth month, placing you solidly in the early second trimester.
Why the Week-to-Month Math Gets Confusing
Calendar months aren’t all the same length, and pregnancy months don’t map perfectly onto four-week blocks. The first trimester spans about 14 weeks, or roughly 3.5 months. The second trimester covers weeks 14 through 28. So “4 months” falls in the early portion of the second trimester, but depending on whether a source rounds up or down, you’ll see the fourth month listed as weeks 13 to 16, 14 to 17, or even 16 to 20.
The simplest way to think about it: if you’re at week 16, you are 4 months pregnant. If someone tells you they’re 4 months along and you want to picture the timeline, think weeks 14 to 17 as the range they’re likely in.
What’s Happening With Your Baby
By the end of this stretch, your baby measures about 4¾ inches from the top of the head to the bottom of the torso and weighs around 4 ounces, roughly the size of an avocado. The skeletal system is hardening from soft cartilage into bone. Facial features are becoming more defined, and the eyes are shifting from the sides of the head toward the front of the face.
This is also when you might first feel your baby move, a sensation called quickening. Most people notice it somewhere between weeks 16 and 24. If this is your first pregnancy, it’s common not to feel anything until after week 20. Early movements often feel like flutters, gas bubbles, or a light tapping rather than distinct kicks.
How You Might Feel at 4 Months
The fourth month is when many people start to feel noticeably better. The nausea and exhaustion of the first trimester typically ease up, and your energy levels climb. That said, a new set of symptoms tends to show up.
Your belly and breasts are visibly growing as your uterus expands. Lower back pain can start as your center of gravity shifts and pregnancy hormones loosen your ligaments. You may also notice nasal congestion or nosebleeds, because increased blood volume causes the lining inside your nose to swell. Gums that bleed when you brush or floss are another common side effect of this extra blood flow.
Skin changes often become visible now. Some people develop brown or gray patches on the face (melasma) or a dark vertical line running down the belly (linea nigra). Stretch marks may appear on the belly, breasts, thighs, or buttocks. Small spider veins can show up on the face and legs. These changes are driven by hormones and increased circulation, and most fade after delivery.
Other symptoms to expect: occasional dizziness from shifts in blood pressure, nighttime leg cramps, increased vaginal discharge that’s clear or white, and mild tightening sensations in your belly known as Braxton Hicks contractions. Urinary tract infections are also more common during pregnancy, so pain or burning during urination is worth mentioning to your provider promptly.
Screenings Around This Time
The fourth month is when the quad screen is typically offered. This blood test checks for markers that indicate the likelihood of certain chromosomal conditions and neural tube differences. It can be done between weeks 15 and 22, but results are most accurate between weeks 16 and 18, right in the heart of the fourth month.
If you haven’t already had an anatomy ultrasound, it’s usually scheduled for sometime between weeks 18 and 22. That scan provides a detailed look at your baby’s organs, limbs, and overall growth, and it’s often the appointment where sex can be determined if you want to know.
Weight Gain and Nutrition
During the first trimester, total weight gain is typically modest, somewhere between 1 and 4.4 pounds. Starting in the second trimester, the expected pace picks up. For someone who began pregnancy at a normal weight, the guideline is about 1 pound per week through the second and third trimesters. If you started pregnancy overweight, the target is closer to 0.6 pounds per week. For those with a higher starting BMI, roughly half a pound per week is the general recommendation.
These are averages, not rigid rules. Weight gain doesn’t happen in a perfectly steady line, and some weeks you’ll gain more or less. What matters most is the overall trend across the trimester rather than any single weigh-in.