Human embryology again

Returning to the topic of human embryology, here is a human fetal timeline for the first 16 weeks post fertilisation (obstetricians count from the LMP = last menstrual period, which adds about 2 weeks). It is a little disturbing quite how much scientific misinformation is being circulated in regard to the topic. False information is not conducive to honest debate, and is highly corrosive of the trust people have in professionals such as scientists (it’s also unethical on both religious and Kantian grounds). In particular, contrary to what some have suggested:

Fetal length data in the table is mostly from here. Except where indicated, linked images are subsequent to miscarriage or to surgery to resolve ectopic pregnancy, so may be distressing to some readers.

Week post fertilisation Week post LMP Fetal length Image
1 3 0.01 cm / 0.005 inches 8–cell image
2 4 0.02 cm / 0.008 inches
3 5 0.1 cm / 0.04 inches heart begins beating at 21 days
4 6 0.5 cm / 0.2 inches image on flickr
5 7 1 cm / 0.4 inches image on wikimedia
6 8 1.6 cm / 0.6 inches image on flickr
7 9 2.3 cm / 0.9 inches image on flickr
8 10 3.2 cm / 1.3 inches
9 11 4.1 cm / 1.6 inches
10 12 5.4 cm / 2.1 inches
11 13 6.7 cm / 2.6 inches ultrasound image
12 14 14.7 cm / 5.8 inches
13 15 16.7 cm / 6.6 inches
14 16 18.6 cm / 7.3 inches
15 17 20.4 cm / 8 inches ultrasound image
16 18 22 cm / 8.7 inches

Below (from here) is a chart of heart development: