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The First Trimester of Pregnancy

The first trimester of your pregnancy is an exciting time, full of many changes for you and especially for your baby, which is just 12 short weeks,  grows from a single cell to a tiny being with a beating heart and functioning kidneys. With all that change going on in your baby, you can certainly expect many changes in your own body, from fatigue and nausea. Pregnancy begins when the egg (or oocyte) and sperm meet, which happens in the fallopian tube. At this stage, the egg and sperm together form what we refer to as the zygote — a single cell. The zygote divides many times into a cluster of multiple cells called a blastocyst, which travels down the fallopian tube and into the uterus (also called the womb). When it reaches the uterus, both you and your baby begin to experience major changes.

A woman’s body goes through many changes during the first 12 weeks of pregnancy. Women often start to have concerns over:

  • what to eat
  • which types of prenatal tests they should consider
  • how much weight they might gain
  • how they can make sure their baby stays health

What Changes Occur in the WOmen’s Body in the First Trimester?

Your baby isn’t the only one growing and changing during your pregnancy. Your own body also has to adjust, and the adjustments it makes aren’t always the most pleasant and comfortable for you. Being prepared for what lies ahead can help ease your mind. In the following section, we are going to list changes in the first trimester as:

  • Breast Changes
  • Nausea
  • Fatigue
  • Bloating
  • Frequent Urination
  • Headaches
  • Constipation
  • Cramps

Tips to Overcome the Effect of Changes during the First Trimester

1. Nausea

Unfortunately, we can’t tell you how to make your nausea totally disappear. But you can try a few things to make it better. Here are some suggestions:

  • Eat small, frequent meals, so that your stomach is never empty.
  • Don’t worry too much about adhering to a balanced diet initially; just eat whatever appeals to you.
  • Avoid perfume counters, active kitchens, smelly taxicabs, barnyards, or other places where odors may be strong.
  • If your prenatal vitamins make the symptoms worse, try taking them at night just before you go to bed. If you find that they are still causing a problem, skipping them for a few days is okay.
  • Ginger (in the form of tea or tablets, for example) may help some women.
  • Try eating dry toast, saltines, whole-wheat crackers, potatoes, and other bland, easy-to-digest carbohydrates.
  • If you’re bothered by the accumulation of saliva in your mouth, sucking on lemon drop candies may be helpful.
  • Relaxation exercises and even hypnosis work for some women.

2. Constipation

About half of all pregnant women complain of constipation. When you’re pregnant, you may become constipated because a large amount of progesterone circulating in your bloodstream slows the activity of your digestive tract. The iron in prenatal vitamins may make matters worse. Try these suggestions to deal with the problem:

  • Eat plenty of high-fiber foods
  • Drink plenty of water
  • Take stool softeners
  • Exercise as regularly as you can

3. Headaches

Many pregnant women notice that they get headaches more often than they used to. These headaches may be the result of nausea, fatigue, hunger, the normal physiologic decrease in blood pressure that starts to occur at this time, tension, or even depression. You should follow some suggestion to overcome headache as:

  • Use Caffeine can alleviate the symptoms of Headache but it should not take on a regular basis.
  • Healthy Food and Extra rest can help with these symptoms.
  • Drinking water

How I Can Stay Healthy in the First Trimester?

It’s important for a woman to be aware of what to do and what to avoid while pregnant in order to take care of themselves and their developing baby.

What Should DO:

  • Take prenatal vitamins.
  • Exercise regularly.
  • Work out your pelvic floor by doing Kegel exercises.
  • Eat a diet high in fruits, vegetables, low-fat forms of protein, and fiber.
  • Drink lots of water.
  • Eat enough calories (about 300 calories more than normal).

What Should Restrain?

  • strenuous exercise or strength training that could cause an injury to your stomach
  • alcohol
  • caffeine (no more than one cup of coffee or tea per day)
  • smoking
  • illegal drugs
  • raw fish or smoked seafood (no sushi)
  • shark, swordfish, mackerel, or white snapper fish (they have high levels of mercury)
  • raw sprouts
  • cat litter, which can carry a parasitic disease called toxoplasmosis
  • unpasteurized milk or other dairy products
  • deli meats or hot dogs

What can be Expected During First Parental Visit to Doctor?

On your first prenatal visit, your practitioner will draw your blood for a bunch of standard tests to check your general health, as well as to make sure you are immune to certain infections. Women normally see their doctor once a month during the first trimester.

The following tests are routine:

  1. A standard test for blood type, Rh factor, and antibody status.
  2. Complete blood count (CBC).
  3. VDRL or RPR.
  4. Hepatitis B.
  5. Rubella.
  6. HIV.

Some doctors also include these test during the first prenatal visit as:

  1. Glucose screen.
  2. Varicella
  3. Toxoplasmosis.
  4. Cytomegalovirus (CMV)

The following are evaluated during a first-trimester ultrasound exam:

  1. The accuracy of your due date
  2. Fetal viability
  3. The Fetal abnormalities
  4. Fetal number
  5. The condition of your ovaries
  6. The presence of fibroid tumors
  7. Location of the pregnancy

Changes in First Trimester

First Trimester consists of three months (12Weeks). We will describe all changes during this time period.

Week 1

The uterine lining (endometrium) has built up during the previous month’s cycle to prepare to receive a fertilized egg. If conception has not occurred, the thickened lining is shed. The
onset of this menstrual period is recognized as the start of pregnancy if conception occurs this month. A woman who is planning to conceive may already be taking folic acid, eating
healthily, and taking regular exercise so that her body is in the best possible condition to begin a pregnancy. To maximize the chance of conception, she may also be tracking her basal body
temperature and changes in cervical mucus in order to detect when ovulation occurs. Hormonal changes during menstruation prompt several ovarian follicles in each ovary to start ripening,
although usually only one fully develops.

When a mature egg is released from an ovary, it travels down the Fallopian tube towards the uterus. If the woman has sex during this fertile time, the sperm will swim up the Fallopian tube to meet the egg, and fertilization may occur.

Week 2

Once the menstrual flow has ceased, cyclical hormonal changes, controlled by the pituitary gland in the brain, encourage the endometrium to start to thicken again in preparation for a possible pregnancy. At the same time, the ovarian follicles continue to ripen. Towards the end of this week, one of these follicles will become fully mature and rupture on the surface of one ovary. Ovulation is marked by a sharp rise in basal body temperature (the body’s lowest temperature when at rest) and thin, stretchy cervical mucus. After ovulation, the egg is captured by tiny fronds (fimbriae) at the end of the Fallopian tube and wafted down the tube, ready to meet any sperm that may arrive. Sex now, around day 14 of the cycle, has the best chance of leading to conception.

Week 3

Up to 350 million sperm are released in a single ejaculation, but fewer than 1 in 1,000 manage to pass through the cervix into the uterus, and only around 200 reach the correct Fallopian tube to meet the egg. At the moment of conception, a single sperm is drawn into the egg, which then blocks entry to others. The fertilized egg produces a hormone called human chorionic gonadotrophin (hCG) that “switches off” the menstrual cycle by stimulating continued production of progesterone, the hormone needed to maintain the endometrium. The egg
moves down the Fallopian tube and divides, forming a two-celled zygote and then a cluster of smaller cells called blastomeres. By the time it reaches the uterus, it is a ball of around 100 cells called a blastocyst.


Sexual positions where the penis is high in the vagina help with conception; raised legs after sex may also help.

Week 4

The blastocyst arrives in the uterus on average six days after conception – the endometrium is now thickened, ready to receive and nourish it. Hormones also thicken cervical mucus so that it
forms a plug in the cervix, which protects the uterus during pregnancy from infections that might otherwise travel up from the vagina. The blastocyst now develops a fluid-filled cavity,
creating two layers of cells. The outer layer (trophoblast) burrows into the endometrium and will become the placenta. The inner cell mass forms the early embryo (embryoblast) – these cells
then differentiate into a two-layered embryonic disc. The fluid-filled cavity develops into a yolk sac that will provide nourishment for the embryo during the early weeks until the placenta has developed.


Even if the pregnancy is still unconfirmed, it is vital to eat a healthy diet to support and nourish a potential embryo.

Week 5

The two-layered embryonic disc develops into a three-layered disc. The outer layer (ectoderm) forms the neural tube that will develop into the brain and spinal cord. Skin, hair, nails, and sweat glands also develop from this layer. The mid-layer (mesoderm) develops into many structures, including the heart and the skeleton. From the inner layer (endoderm), the thyroid gland, lungs, intestines, and pancreas will form. The early placenta – known as the chorionic villi – starts to develop and form blood vessels, yet nourishment still comes from the yolk sac at this stage. A pregnancy test may now register positive, even before the woman realizes she has missed a period, and she may experience symptoms such as nausea, bloating, increased urinary frequency, and breast tingling.


Over-the-counter pregnancy tests detect the hormone hCG, which is produced when the embryo implants.

Week 6

The embryo reaches around 4mm (3/16in) long, and its body curves over into a C-shape. It has a small primitive tail, and limb buds start to sprout from the trunk. Dark spots appear on the face as
eyes form, and tiny pits either side of the head will eventually become the ears. The heart is the first organ to develop, reflecting the embryo’s increasing need for sustenance as it grows. It forms
from two tubes that fuse then divide into separate chambers. It now beats at between 100 and 140 beats per minute, pumping blood around the body, and can be seen on an ultrasound scan. The embryo’s central nervous system develops connections to early muscles, and the embryo may start to move, although the woman will not feel its movements until much later on in the pregnancy.


Some women may notice they have gained a small amount of weight by week six. This is perfectly normal and healthy.

Week 7

The embryo continues to grow rapidly to around 8mm (5/16in) long – about the size of a kidney bean. The limb buds develop paddle-shaped ends from which fingers and toes will form. The lens and retina, begin to develop in the rudimentary eyes, and the liver forms and begins producing red blood cells. Veins become apparent under the Fetus’s skin. The yolk sac starts to shrink as the developing chorionic villi increasingly supply the embryo with oxygen and nutrients from the maternal bloodstream. The woman’s clothing may now start to feel uncomfortably tight around the waist. Dietary tastes often change, and some women develop aversions to particular foods. In some women, increased circulating blood volume may give rise to headaches.


Many pregnant women develop either an increased sensitivity or aversion to particular smells and tastes.

Week 8

By the end of the second month, the embryo measures about 1.4cm (1/2in) long, the size of a raspberry, and all major organs have started to form. The primitive tail begins to disappear, and limbs lengthen and develop webbed fingers and toes. Unique fingerprints have already formed. As the elbows develop, the arms curve and can move. The brain matures further, and heart valves form so that the primitive circulation flows in the right direction. The lungs continue to grow, and airways develop that connect them to the back of the throat. The mother’s uterus is now the size of a small grapefruit and may press on the lower spine, sometimes causing backache. Her waistline is now thicker, and her breasts may appear bigger, though she will still not look noticeably pregnant to others.


The three main sections of the brain are now visible as bulges, and the cranial and sensory nerves start to develop.

Week 9

The embryo now measures around 1.8cm (3⁄4in), about the size of a large grape, and its tail has disappeared. Fingers start to separate, and the wrists bend and move. The nose takes shape, the mouth and lips are almost fully formed, and the eyelids fuse over the eyes, which will not open again until around the 26th week of pregnancy. The diaphragm, a muscular sheet that will eventually separate the chest and abdominal cavities, starts to form, and the bladder and urethra separate from the lower end of the intestinal tract. The placenta supplies most of the embryo’s nourishment, and the yolk sac shrinks further. The woman may notice more weight gain; this is mainly due to fluid retention and increased blood volume. Her breasts will probably be noticeably larger and may feel tender.


Some women may have their first antenatal appointment around nine weeks. It can be with a midwife or a doctor.

Week 10

The embryo officially becomes a fetus in the eighth week of development post-fertilization (the 10th week of pregnancy). It is now around 3cm (11⁄4in) long, about the size of a prune, and
able to move vigorously. The head is almost half its length, with recognizable facial features and ears. Cartilage in the skeleton begins to harden into bone (ossify), and toenails appear. Hormones prompt the primitive gonads to develop into ovaries or testes, and the ovaries start producing eggs. The external genitals start to differentiate too, but it is not yet possible to tell male from female. Buds from the bladder grow upwards to join with tissue in the pelvis that will eventually become the kidneys. The woman’s respiratory system begins to adapt to meet the demands of pregnancy.


At around 10 weeks, fetal cartilage starts to harden and ossify into bone, aided by cells brought in by the blood supply.

Week 11

The fetus is now around 5cm (2in) long, about the size of a plum. It can open and close its mouth, enabling yawning and swallowing. Tiny teeth buds are forming within the jaw, fingers and toes start to lose their webbing, and the skin thickens and loses its previous transparency. The heart is beating faster, between 120 and 160 beats per minute, and blood is circulating rapidly around the fetal body. The woman’s abdomen may protrude a little, and she may feel increasingly breathless on exertion due to the increased workload of the heart and lungs. The enlarging uterus now moves upwards out of the pelvis, reducing pressure on the bladder, so urinary symptoms lessen, but existing varicose veins or hemorrhoids (piles) may swell up, or new ones may develop.


The 3D ultrasound image of an 11-week-old fetus will show a relatively large head and well-developed face.

Week 12

The fetus is now on average 6cm (21⁄4 in) long, about the size of kiwi fruit. As brain cells multiply rapidly, the brain develops into two distinct halves (left and right hemispheres) – each one controls the opposite side of the body. Developed reflexes mean the fetus may move in response to pressure on the abdomen, suck a thumb or fist, and urinate. It begins to produce its own hormones, and the genitals may show the first outward signs of gender. Some women now appear pregnant and may have to adjust clothing to accommodate the bump. Hormonal changes can cause nipples and areolae to darken, although this will be more pronounced later on. Often any nausea now passes, appetite improves, and early pregnancy tiredness gives way to increased energy.


Most women have their first ultrasound scan at around 12 weeks. The scan is a useful way to date the pregnancy.

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