PREGNANCY

ONCE UPON A MONTH

… and once EVERY month….

› An egg or OVUM is released from the ovaries and takes 2-3 days to travel (by means of cilia) through the oviduct to the uterus

CONCEPTION

When the sperm and egg come together (i.e. sperm fertilizes egg)

If you don’t already know this, write it down.

EARLY STAGES OF PREGNANCY

During the ZYGOTE stage, the mother may not know she is pregnant

The First Two Weeks

Pregnancy begins at the moment of conception› Two gametes ( a

sperm and an egg cell ) combine to give a complete set of chromosomes to new individual -- ZYGOTE

The Zygote begins to divide about 36 hours after conception.

Zygote after 2 divisions

Blastocyst

After 3 days, cell divisions have produced a ball full of cells (called a MORULA) the same size as original zygote.

Continued cell division forms the blastocyst (hollow ball of cells) which embeds in uterine lining around day 7

http://www.pbs.org/wgbh/nova/miracle/program.html

Signs of Pregnancy The symptoms arrive around time of implantation (day 7). They include:› Missed period› Inability to bear certain foods› Sensitivity to odors› Discomfort or tenderness in breasts› Morning nausea› Possibly cravings for certain foods

These symptoms may or may not be present… every woman and every pregnancy is different

Complaints During Pregnancy

Nausea (“morning sickness”) usually doesn’t occur after the 4 month mark

Shortness of breath Heartburn Strange cravings Varicose veins Lower back pain

(caused by change of posture)

Even more possible complaints Excessive discharge Quick weight gain Excessive thirst Headaches Hands, face, or feet swelling Muscle cramps in legs

Period of the Embryo

Week 3 – 8 All major body systems begin to form Placenta forms

› Pancake-like shape, has a cord that connects it to baby’s navel (umbilical cord)

Size of embryo – ¼ inch to 1 inch long Pregnancy may still be unknown to

mother

Living in amniotic fluid requires the baby to obtain its oxygen through the umbilical cord and placenta

3 weeks – heart and nervous system begin to form

Week 5 – brain starts to develop, arm and leg buds can be seen

Eyes & lungs begin to develop

Crucial time in development – first 2 – 3 months

Awareness of pregnancy is important early because of the harm that can be caused by alcohol, viral infections, x-rays and drugs.

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TERATOGENS

External agents such as viruses, drugs, chemicals and radiation that can harm a developing embryo or fetus.

Time when organ system or body part is at highest risk of effects from teratogens is known as ‘sensitive period’.

Effects of teratogens on a body part or organ system are worst during the period when that structure is forming and growing most rapidly.

TERATOGENS CONT’D….

The same defect can be caused by different teratogens.

A variety of defects can be caused by a single teratogen.

The longer the exposure or the higher the ‘dose’ of the teratogen, the more likely it is that serious harm will be done.

The long-term effects of a teratogen often depend on the quality of the postnatal environment.

Period of the Fetus 15 week old fetus

From week 8 – birth 3rd month – spontaneous movement By end of 3rd month all organs and major

systems have developed, use rest of time to mature

Movement can be felt between 4th & 5Th month

Full term between 37 – 40 weeks Most rapid growth occurs from 3rd & 7th

month (approx 12 inches)

Fetal Development

5th month – skeleton hardens (cartilage replaced by bone)

A 6-month old fetus can live in an incubator if born at this time

7th month – movement gets difficult – too big, head down position

8th & 9th month – fat is formed rapidly, sensitive to noise, sucks thumb, hiccups, sneezes, yawns. Aquires immunity from mother’s blood

Full term at between 37 and 42 weeks

Maternal and Fetal Health…..an important job for mother-to-be

The child’s life and health depends on the mother and her activities/lifestyle

Drugs, alcohol, even diet or sleeping pills, antibiotics, tranquilizers, pep pills, laxatives, painkillers can have effects on a developing fetus…

Ways drugs can affect fetus:

Change mother’s physiology, affecting environment of uterus

Cross the placenta unchanged and affect fetus in same way as mother, eg slowing down breathing and heart rates(barbiturates)

Narcotics – herion, cocaine, LSD can cause birth defects› Most importantly,

baby can be born addicted, suffering painful withdrawal

Alcohol

All forms of alcohol pass through placenta to fetus.

It stays in the fetal body system longer than the mother, because of baby’s immature liver

Baby may have serious impairment

Mental handicaps, behavioral problems, learning disabilities, and heart defects

FAS (fetal alcohol syndrome) can occur when mothers drink (usually to babies of heavy drinkers)

Smoking

Nicotine and CO enter mom’s blood when smoking› Then into baby’s

blood Baby’s heart rate

increases too

Smoking

Increases risk of:› spontaneous

abortion› bleeding during

pregnancy› damage to fetal

heart› low birth weight› premature birth