6th week: The heart starts to beat
- Weeks and days
- 5+0 to 5+6
- Month
- 2
- Trimester
- 1
This week, the embryo grows from about 1.5 to 5 millimeters. At around 5+1, its heart beats for the first time; on ultrasound, it can usually be seen from about 5+6.
Week 6 of 40
Calculate your weekHow big is the embryo?
1.5 to 5 mm
In one week, the embryo becomes about three times as long. The neural tube, from which the brain and spinal cord develop, closes, and at the end of the week the first beginnings of the arms appear.
Length according to the Carnegie stages of embryology. On ultrasound, the crown-rump length is measured; at around 5+6 it is only about 1 mm.
This week
Your baby
- The heart beats from about 5+1, and blood circulation begins with the heartbeat.
- The neural tube closes by about 6+2.
- The first arm buds form at the end of the week.
Your body
- The median hCG level is 1,398 mIU/ml; 217 to 7,138 is normal. More in the hCG levels chart.
- On average, nausea begins at around 5+4. About one in five women has none at all.
- Around one in four has bleeding in the first trimester, usually light.
What matters now
- Folic acid 400 µg daily. According to the German recommendation, 800 µg if you did not already start taking it 4 weeks before conception.
- Iodine 100 to 150 µg daily.
- Make an appointment with your gynecologist.
Get checked right away: one-sided pain in the lower abdomen, heavy bleeding, pain in the tip of the shoulder, or dizziness. This can be a sign of an ectopic pregnancy.
On ultrasound
- 5+0
Gestational sac is reliably visible as a dark bubble in the uterus.
- 5+5
Yolk sac was visible in all pregnant women by this day.
- 5+6
Embryo with heartbeat was visible from this point in all women with a reliable date.
No heartbeat yet? With an embryo under 7 mm, this is only a suspicion, not a diagnosis. A follow-up check then takes place after 7 days at the earliest.
Frequently asked questions about the 6th week of pregnancy
When can you see the heartbeat on ultrasound?
The heart beats from about 5+1. On ultrasound through the vagina, one study found the heartbeat visible from 5+6 in all women with a reliable date. After IVF, at the earliest 25 days after egg retrieval, that is, at 5+4.
Is it normal to have no nausea in the 6th week of pregnancy?
Yes. About one in five pregnant women has neither nausea nor vomiting during the whole pregnancy. For the others, nausea begins on average at around 5+4.
Does health insurance pay for an ultrasound in the 6th week of pregnancy?
In Germany, an early ultrasound is covered by health insurance only if a disrupted early pregnancy is suspected. The first regular ultrasound screening takes place between 8+0 and 11+6.
Which month is the 6th week of pregnancy?
The 2nd month of pregnancy, in the 1st trimester. Figures such as 5+3 weeks also belong to the 6th week of pregnancy.
Sources
- Carnegie stage table, UNSW Embryology
- Heart Development, UNSW Embryology
- Bree RL et al.: Transvaginal sonography in the evaluation of normal early pregnancy, AJR 1989;153:75
- Schats R et al.: Embryonic heart activity, BJOG 1990;97:989
- Doubilet PM et al.: Diagnostic criteria for nonviable pregnancy early in the first trimester, NEJM 2013;369:1443
- Ectopic pregnancy and miscarriage, NICE guideline NG126, updated 17 June 2026
- Gadsby R et al.: A prospective study of nausea and vomiting during pregnancy, Br J Gen Pract 1993;43:245
- Hasan R et al.: Patterns and predictors of vaginal bleeding in the first trimester, Ann Epidemiol 2010;20:524
- Alaze-Hagemann F et al.: Recommendations by the Healthy Start Network 2026 (Handlungsempfehlungen Netzwerk Gesund ins Leben), Geburtshilfe Frauenheilkd 2026;86(6):e60
- Maternity guidelines (Mutterschafts-Richtlinien), Federal Joint Committee (Gemeinsamer Bundesausschuss), in effect since 25 August 2026
- Weeks of pregnancy, familienplanung.de, Federal Institute for Public Health (BIÖG)
- Ectopic pregnancy, NHS, as of 19 August 2026