First trimester · Pregnancy week by week
Week 13 of pregnancy
Baby is the size of a peapod. About 2.90 inches, 23g.
Week 13 is the cusp of the second trimester. Black women face 3x higher preeclampsia mortality per CDC PMSS — preeclampsia onset is rare before 20 weeks, but this is the week to start tracking BP at home if you're high-risk. Source
What's happening with the baby
The fetus has fingerprints. Vocal cords are forming. The pancreas, liver, and intestines work. Bone marrow makes white blood cells. The fetus is now nearly 3 inches long.
What's happening for you
Most women feel substantially better by week 13. Energy returns. Many report a 'second wind.' The uterus has fully risen out of the pelvis and is palpable. Hair and nails grow noticeably faster.
Common (normal) symptoms this week
Energy returning, occasional headaches, increased appetite, breast continuing to grow, mild round-ligament pain when changing positions, slight visible bump.
Call your OB or 911 if
- Severe abdominal or one-sided pelvic pain with bleeding — possible ectopic pregnancy.
- Heavy vaginal bleeding (soaking a pad in an hour) with cramping.
- Fainting, severe dizziness, or shoulder-tip pain — ectopic with internal bleeding is an emergency.
- Fever over 101°F with chills or pelvic pain.
- Severe vomiting that prevents keeping any fluids down for 24+ hours (hyperemesis).
Why this week matters for Black families
By the end of the first trimester, several decisions matter for Black families. (1) Whether to do first-trimester genetic screening (NIPT). The Bonus uptake rate for NIPT is lower for Black patients, and the literature documents that providers offer it less often — if you want it, ask explicitly. (2) Documenting baseline blood pressure. Pre-existing chronic hypertension is more common in Black women and changes the entire prenatal-care plan. (3) Asking about low-dose aspirin for preeclampsia prevention. Per the USPSTF 2021 recommendation, Black patients are in the high-risk category for which aspirin from 12 weeks onward is supported by RCT evidence.
What to do this week
If you have a home blood pressure cuff, start tracking baseline. Continue aspirin if prescribed. Schedule the 16-week appointment. If you have a known sickle cell trait or disease, ensure your hematologist is co-managing — pregnancy with sickle cell carries elevated risks for both mother and baby and the management plan should be in place by now.
References
- CDC Pregnancy Mortality Surveillance System.
- ACOG Committee Opinion 821 — Sickle Cell Disease in Pregnancy.
Last medically reviewed: .
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