Week 13 is the first week of the fourth month of pregnancy. At this time of pregnancy, ossification of the cartilage tissue begins and the bones harden.
In addition, the kidneys become functional and the foetus' body is covered with lanugo, a fine hair that falls out before birth.
Read the full article on: What Happens During the 4th Month of Pregnancy? ( 74).
By Elena Izquierdo Trechera M.D., M.Sc. (gynecologist), Marta Barranquero Gómez B.Sc., M.Sc. (embryologist), Rebeca Reus BSc, MSc (embryologist) and Sandra Fernández B.A., M.A. (fertility counselor).
Last Update: 01/04/2023
