Pregnancy Milestones by Trimester

First Trimester

During the first three months of pregnancy, your baby’s basic organ system begins to develop. You’ll be tired more often, and will likely have to use the bathroom more often. Some pregnant women also experience constipation. Some milestones you may hit include:

• •4 weeks: A ball of cells called a blastocyst has officially become an embryo, roughly the size of a poppy seed. This is when organ development begins, lasting approximately six weeks.
• •5 weeks: The baby’s heart begins to beat, generally at about twice the rate of an adult heart.
• •6 weeks: Facial features begin to form, and little buds for the arms and legs start to develop.
• •10 weeks: The embryo officially becomes a fetus. Organs like kidneys, intestines, brain, and liver are beginning to function, and fingernails and toenails are starting to form.
• •12 weeks: You’ll likely be able to hear the baby’s heartbeat at a prenatal checkup, though this may have already happened at an ultrasound.

Second Trimester

By the beginning of the second trimester, many mothers feel more energetic and have less nausea—though some experience more headaches. It’s important to stay hydrated during this period. Certain milestones include:

• •14 weeks: The baby’s kidneys are producing urine that’s released into the amniotic fluid. The baby can make facial expressions and may begin sucking his or her thumb.
• •16 weeks: The baby’s gender might be detectable at a mid-pregnancy ultrasound, which is generally done between 16 and 20 weeks into pregnancy.
• •18 weeks: If you haven’t already felt the baby moving around in the womb, you likely will around this time. Within a couple weeks after that, other people should be able to feel baby movements from outside your stomach.
• •23 weeks: The baby’s sense of motion has developed, and hearing continues to improve.
• •24 weeks: taste buds are developing, and both the brain and hair should be growing quickly. The baby may weigh just over a pound and be up to a foot long.
• •27 weeks: Though they won’t be functional for a few more weeks, the baby’s lungs are developing quickly. The baby will inhale and exhale amniotic fluid and will have begun sleeping and waking at regular intervals. They’ll also likely begin opening and closing their eyes and sucking on their fingers