During the fourth month of pregnancy, the foetus is covered with a layer of very fine hair called lanugo. This hair serves as a means of protection against the cold, which is why lanugo covers almost all of the baby's body.
On the other hand, it is important to mention that at around the 15th week of pregnancy, the baby's facial muscles can already perform the sucking movement and the baby can suck its thumb.
The increase in size of the foetus during this fourth month of gestation means that the woman's belly begins to increase in size and, therefore, the pregnancy is already quite evident externally.
Read the full article on: Pregnancy Stages by Month – Fetal Development with Pictures ( 79).
By Andrea Rodrigo B.Sc., M.Sc. (embryologist), Marta Barranquero Gómez B.Sc., M.Sc. (embryologist), Silvia Jiménez Bravo B.Sc., Ph.D. (senior clinical embryologist), Silvia Azaña Gutiérrez B.Sc., M.Sc. (embryologist) and Marie Tusseau (invitra staff).
Last Update: 03/07/2023
