Transcript File

Misconceptions about
Conception
Menstrual cycle is not always 28 days.
Ovulation does not always occur on day 14.
It is true that there is a fixed amount of time
between ovulation and menstruation, usually
12-16 days.
Conception can only within 24 hours after
ovulation; however, women are considered
“fertile” for 2-3 days before
ovulation.Maximum fertile day is day of
ovulation.
Necessary ingredients to
conception
An ovum, or egg that has been released
Sperm (average ejaculate contains 300350 million sperm)
Fertile-quality, “eggwhite” cervical fluid
for the sperm to swim in
Fertile quality cervical fluid
Where conception occurs
Once the egg has been released, it is
pulled from the ovary into the fallopian
tube.
Most conceptions occur in the outer
third of the fallopian tube.
The fertilized egg is called a zygote.
Corpus luteum
When the egg is released, a yellow spot
is left behind on the ovary where the
egg was. This is the corpus luteum.
Function of the corpus luteum: to
secrete hormones to prepare the uterine
lining to receive a fertilized egg.
If fertilization does not occur
The corpus luteum shrinks
Progesterone levels fall dramatically
Uterine lining is discarded through the
menstrual cycle approximately 14 days
past ovulation.
Zygote’s journey to the uterus
It takes 7-9 days for zygote to go from the
fallopian tube to the uterus
Pulled along by the cilia of the fallopian tube
Then it implants in the uterine wall.
If you experience spotting (light bleeding)
about 7-9 days after you ovulate, then there’s
a good chance you’re pregnant. Called
implantation bleeding.
hCG
After the zygote has burrowed into the
uterus, it starts releasing human chorionic
gonadotropin hormone (hCG)…the pregnancy
hormone.
It is the presence of this hormone that
pregnancy tests detect.
Function of hCG is to send a message back to
the corpus luteum to stay alive and start
producing progesterone.
Role of Progesterone
Progesterone keeps the uterine lining from
shedding.
Many very early miscarriages result from lack
of progesterone.
Taking progesterone supplements in early
pregnancy can prevent a miscarriage.
Placenta eventually takes over progesterone
production from the corpus luteum.
Fertility rates by age
Age
15
25
35
45
Rate per cycle
40-50%
30-35%
15-20%
3-5%
General facts about pregnancy
Pregnancy lasts for 266 days on average.
Doctors count first day last menstrual period
(LMP)—not the day you conceive--as the first
day of pregnancy
According to the medical model, pregnancy
lasts 40 weeks; it’s actually 38 weeks from
the time of conception until birth (on
average).
Three distinct periods of
development
Period of the zygote (weeks 1-2)-also
called the germinal period
Period of the embryo (weeks 3-8)
Period of the fetus (weeks 9-38)
**These are not the same as first,
second, and third trimester
Period of the zygote (germinal
period)
First two weeks after conception
Period of rapid development
Zygote becomes the blastocyst--hollow inner
layer of cells, which implants into the uterine
lining on days 7-9
Trophoblast—outer layer of cells; becomes
the placenta
Differentiation of cells begin
30-50% of conceptions don’t make it through
this period
Placenta is formed at the end of this stage
Life support systems of the
embryo
Amnion—sac filled with clear fluid in which
embryo floats
Placenta—disk-shaped group of tissues that
allows food and oxygen to reach the embryo;
carries waste products away
Umbilical cord—contains two arteries and one
vein that connect the baby to the placenta.
Embryo’s and mom’s blood supplies come in
close contact but never mix directly
Placenta at around 8 weeks
Developmental trends
Cephalocaudal—from head to tail;
development occurs head-down
Head region accounts for 50% of total
length during the first month
Proximodistal—development occurs
“from the inside out”—midline outward
Same pattern of development
throughout childhood
Period of the embryo
Dramatic and rapid growth takes place
Groundwork for all body structures and
internal organs is laid
By the end of this period, all of the
structures and internal organs a baby is
born with are already formed
By the end of this period, embryo loses
its gills and tail and looks more human.
The embryo at 6 weeks
Embryonic development at 8
weeks
Embryo is 1 ½ inches long and 1 oz. In
weight
Arm and leg differentiate further
Elaborate peripheral nervous system in place
Glandular system operating
Internal sex organs developed (NOTE: Sex is
determined at conception.)
Embryo can move, but movements can’t be
felt by mom yet.
8-week-old embryo
Early Period of the fetus
(weeks 9-12)
Embryo becomes a fetus when bone replaces
cartilage
Facial features become distinct, human-like
Vocal cords, nails, lungs have formed
External genitalia are identifiable
Heartbeat can be heard
Baby can urinate
Baby can smile, frown, suck, and swallow
About 3 inches long; weighs about 1 ounce
Middle months of period of
the fetus (5th-6th month)
12-15 inches long, 12-32 ounces
Grasping reflex
Lung breathing is possible
Sleep/wake cycles similar to newborn’s
Eyes and ears are sensitive to light and sound
Grasping reflux; baby sucks thumb
All neurons present by 24 weeks’ gestation
Vernix and lanugo
Appear in 5th-6th month
Vernix—cheeselike covering to protect
skin from chapping
Lanugo—white, downy hair on body to
protect skin from chapping
Fetus with vernix and lanugo
Vernix and lanugo are often still present
at birth, especially if the baby is
preterm.
Age of viability
This is the age by which the fetus can
survive outside the womb
Usually this is between 22-26 weeks’
gestation
By the 24th week, the fetus has a 50%
chance of survival.
Last months (7-9) of
pregnancy
Lungs gradually mature
Rapid brain development causes sensory &
behavioral capacities to expand
Antibodies are transferred from mom to baby
Baby becomes better able to regulate
temperature
Gains 3.5 pounds in fat
Engagement (baby’s head in birth canal) by
36 weeks
Baby weighs on average 7 ½ pounds at birth
Sex Differences in Utero
Males are more physically active—they
remain more active through childhood
Females are more sensitive to external
stimulation
Females advance more rapidly in skeletal
development and are 1-2 weeks ahead of
males in bone development at birth. Trait
remains through early adolescence.
More boys are conceived than girls, but the
birth rate is roughly equal (105 males to 100
females)
Mozart effect
The finding that exposing fetuses and
babies to classical music (specifically
Mozart) is associated with greater math
and spatial ability test scores.
The finding has been disputed recently.
Seems to increase math skills in adults
for about 30 minutes after listening to
it.
Sounds and tastes infants
prefer
They prefer their mother’s voice over all
others
No preference in father’s voice over other
men’s
Fetuses develop taste preferences and
aversions; strong tastes such as garlic are
present in the amniotic fluid (also in breast
milk)
Fetal tastes may influence later taste
preferences.
Habituation
Getting accustomed to a certain
stimulus in the womb
Fetuses at 26 weeks of age show
habituation to repeated stimuli
Some psychologists think that how
quickly a fetus habituates to a routine
stimulus predicts future intelligence.
This is debatable.
Teratogens
Any environmental agent that can interfere
with the process of normal growth (even
vitamins can be teratogens)
Especially harmful in the embryonic stage
because this is when organs are being
formed.
Effects of a teratogenic substance are worse
on the body part or organ systems that are
being formed at the time of exposure
Does a teratogen always
cause damage?
No—a specific teratogen usually does NOT
cause a specific birth defect.
Three factors influence the effects of a
teratogen:
Dose—the greater the dose, the greater the
effect.
Genetic susceptibility—both the mother’s and
baby’s genotypes influence vulnerability.
Timing—Teratogens do more damage at specific
times of development.
Why are teratogens harmful
to baby but not to Mom?
Mother weighs a lot more
Mother’s organs aren’t developing like
the baby’s are
The placenta and immature fetal liver
may be unable to convert a harmful
substance to a harmless one
Examples of teratogens
Over-the-counter, prescription, and illegal
drugs
Caffeine—medical opinions differ as to
whether it’s harmful or not (4 cups or more of
coffee a day is considered harmful)
Tobacco—associated with low birth weight,
miscarriage, SIDS, asthma, and childhood
cancer
Alcohol—can result in fetal alcohol syndrome
Maternal malnutrition—smaller brain size
Maternal stress—associated with miscarriage,
Fetal alcohol syndrome
Involves mental retardation, impaired
motor coordination, poor attention and
memory, and certain physical
characteristics.
Prematurity
Babies born 3 weeks or more before the end
of pregnancy OR who weigh less than 5.5
pounds
Birth weight is best predictor of infant
survival and healthy development
Best scenario is to be at least 2 pounds at
birth and 32 weeks’ gestation
Preterm babies are more difficult infants than
other babies are and have a greater risk for
abuse.
Three stages of birth
Stage 1: cervix dilates and effaces (thins
out)…goes from totally closed to 10 cm
(completely open). Lasts 12-14 hours on avg.
in a first birth, 4-6 hours in subsequent births
Stage 2: the stage where the baby is pushed
out. Lasts around an hour in a 1st birth, 15-20
minutes in later births.
Stage 3: placenta (“afterbirth”) is delivered.
Usually occurs 5-10 minutes after baby is
born; this is usually not felt by the mother.
C-sections
C-section rates are currently 20-25% in US;
varies by hospital
Main reason for C-section: having had a prior
C-section.
Fetal distress, prematurity, certain maternal
illnesses (such as HIV), birth canal being too
narrow, and labor that doesn’t progress are
reasons for C-sections.
Push by some OB/GYNs to give women the
right to elective C-sections.