Fetal period
Lecturer Dr. Firdous M. Jaafar
HHDTD Module
Objectives
1- define fetal period.
2- follow the changes that occur in the fetus
from 9
th
week till term.
3- determine the methods to calculate date of
birth.
4- recognize some clinical conditions related to
birth weight .
Fetal period
The period from the beginning of the ninth week to birth
It is characterized by maturation of tissues and organs
and rapid growth of the body.
The length of the fetus is usually indicated as the crown-
rump length (CRL) (sitting height), or as the crown-
heel length (CHL), the measurement from the vertex of
the skull to the heel (standing height).
These measurements are expressed in centimeters.
Growth in length is particularly striking during the third,
fourth, and fifth months, while an increase in weight is
most striking during the last 2 months of gestation.
9- week fetus
Monthly Changes
relative slowdown in
growth of the head
compared with the rest
of the body.
At the beginning of 3
rd
month:
-The head constitutes half
the CRL, eyes move to
the ventral aspect of
the face, ears at the
side of the head .
Monthly changes
Week 12:
Primary ossification centers
appears.
Upper limbs have almost
reached their final relative
lengths, lower limbs still
underdeveloped .
External genitalia are
established .
Physiological hernia is reduced
.
Beginning of muscular activity.
Monthly changes
4
th
and 5
th
month:
Rapid increase in length, CRL
is approximately 15 cm.
Little increase in weight, less
than 500 g.
fetus is covered with lanugo
hair.
movements of the fetus can
be felt by the mother.
Monthly changes
6
th
and 7
th
month:
skin of the fetus is reddish
and has a wrinkled
appearance because of
the lack of underlying
connective tissue.
length is about 25 cm and
weighs approximately
1,100 g.
Monthly changes
8
th
and 9
th
month:
the fetus obtains well-
rounded contours .
skin is covered by a whitish,
fatty substance (vernix
caseosa).
the weight of a normal fetus
is 3,000 to 3,400 g, its CRL
is about 36 cm, and its
CHL is about 50 cm.
Time of birth
The date of birth is most accurately indicated as 266
days, or 38 weeks, after fertilization.
The obstetrician calculates the date of birth as 280
days or 40 weeks from the first day of the LNMP.
ultrasound can provide an accurate (1 to 2 days)
measurement of CRL during the 7th to 14th
weeks, by measurements of biparietal diameter
(BPD), head and abdominal circumference, and
femur length.
Clinical correlates
Low Birth Weight: when the fetal weight is less
than 2500 gm, regardless of gestational age.
Intra uterine growth restriction(IUGR): is a term
used to infant who do not attain their optimal
intra uterine growth.
Small for gestational age fetus (SGA):
Growth is normal but weight does not coincides
the expected for date