What's happening with your baby at 13 weeks
At 13 weeks, your baby is about the size of a peach — roughly 7.4 cm from head to bottom (crown-rump length) and around 23 grams. Tiny fingerprints are forming on their fingertips, and the vocal cords are starting to develop.
Baby's intestines, which have been growing inside the umbilical cord for the past few weeks, are moving into the abdomen this week. The kidneys are functioning well enough to start producing urine, which becomes part of the amniotic fluid.
Bones are beginning to harden, though on an ultrasound baby still looks soft and cartilage-like overall. Baby can make sucking and swallowing motions now, though this doesn't provide any nutrition yet.
How are you feeling at 13 weeks pregnant?
For many people, the nausea and fatigue that peaked around weeks 9 to 11 start to ease around now, though the timing varies a lot and some people feel queasy well into the second trimester. There's no fixed schedule for when it lifts, and that's normal too.
Your uterus is now roughly the size of a grapefruit and may be rising up out of your pelvis, so a small bump can start to show — especially if this isn't your first pregnancy.
Other things people commonly notice this week: increased vaginal discharge, occasional round ligament twinges as your uterus stretches, more visible veins on your chest or legs, and a returning appetite.
First-trimester screening and genetic testing
The nuchal translucency (NT) scan, part of first-trimester combined screening, is usually done between 11 weeks and 13 weeks 6 days, so this may be the week you have it or get the results, depending on your provider's timing.
The NT scan measures fluid at the back of baby's neck and, combined with a blood test and your age, estimates the chance of certain chromosomal conditions like Down syndrome. It's a screening tool, not a diagnosis.
Noninvasive prenatal testing (NIPT), a blood test that can be done from around 9 to 10 weeks, gives information on the likelihood of certain chromosomal conditions and can sometimes give an early indication of sex chromosomes. If a screening result raises questions, your provider may discuss diagnostic options like CVS or amniocentesis.
What to do this week
Keep taking your prenatal vitamin and attend your scheduled appointments, including the NT scan if it hasn't happened yet. This is also a common week for people to start sharing their pregnancy news, since the miscarriage risk drops notably after the first trimester — though there's no rule about when is right for you.
If your clothes are starting to feel tight, this is a good week to pick up a few looser or maternity pieces rather than fighting your waistband.
If your job involves heavy lifting, long standing, or exposure to chemicals, it's worth starting the conversation with your employer or provider about any adjustments you might need.
When to call your provider
Call the same day for heavy vaginal bleeding, severe or persistent abdominal pain, fever, or fainting. These can have straightforward explanations, but they need to be checked promptly rather than watched.
Also call for calf pain or swelling in one leg, which can be a sign of a blood clot, or for severe dizziness that doesn't pass with rest. When in doubt, it's always reasonable to call and ask.