Third Week of Pregnancy

 Your 3rd Week

YOU ARE: 2 WEEKS AND 1 DAY 
265 days to go... 

WHAT’S HAPPENING INSIDE?

 Here the egg is shown surrounded by sperm. Although only one sperm will fertilize the egg, several hundred are thought to be necessary to break down its defensive layers and enable fertilization to take place.

Your newly released egg will only survive 24 hours, but hopefully in that time it will meet sperm and be fertilized.

You are likely to have ovulated and your unfertilized egg now begins its journey. Once it has been released by the ovary, the egg is swept up by one of your fallopian tubes and, moving in the direction of the uterus, comes to rest in the widest portion of the tube, awaiting fertilization. 

It is no exaggeration to say that for each sperm released the chance of even reaching the site of fertilization is in the order of one in a million. Around 300 sperm reach the tube but only one will fertilize the egg. 

Once the sperm has penetrated, it triggers a reaction that makes the surface impenetrable. Each sperm and egg contain 23 chromosomes, half of the total genetic material required. The egg will always contain an X chromosome but the sperm will carry either an X or Y chromosome and therefore determines the sex of the embryo. The sperm and egg chromosomes combine forming the “zygote” and fertilization is complete.

A few hundred sperm survive the journey and encounter the egg in the fallopian tube, but it is just one sperm that actually fertilizes the egg.

FOCUS ON... DADS

Fit but not fertile? 

If you want to become a dad, there are many reasons why you should ensure you’re in good shape, not least to support your partner as she prepares for pregnancy. However, while a couch potato lifestyle isn’t desirable for men who want to conceive, it seems that pulling out all the stops at the gym might not be the best course of action either. 

Researchers asked a group of fit young men to exercise intensively four times a week for two weeks. Afterward, their semen was tested and found to contain fewer sperm and lower levels of the hormones essential for conception. These hormonal changes were temporary and returned to near normal within a few days of the men resuming previous levels of activity. 

The concern is that recovery might not be so fast among older men, or in those who have poor sperm counts and/or low hormone levels. So stay in shape but don’t overdo it

AS A MATTER OF FACT 

The hormones responsible for the production of sperm are released every 60 to 90 minutes. So a man is constantly producing sperm cells

In theory, this means that a male is always fertile, but it takes sperm a 72-day period to fully develop. So leading an unhealthy lifestyle during that time will impinge on the quality. For this reason, if you’re trying to conceive, your partner should embark on a healthy lifestyle for three months to produce good sperm.

Genes and inheritance  

The genes that parents pass on to their children at least partly determine their children’s physical and mental characteristics. In some cases, an abnormal gene may be passed on, resulting in an inherited genetic disorder.

HOW GENES ARE PASSED ON

Through the generations 

Through each generation, genes are shuffled and re-shuffled. Half of a baby's genes come from its father and half from its mother. The baby's parents in turn inherited half each of their genes from each of their own parents. One quarter of each person's genes therefore come from the grandparents. So how does this happen? 

Instead of containing the full complement of 46 chromosomes, each egg and each sperm has just half, or 23, chromosomes each. When they meet at conception the chromosomes pair up to again make up the full complement that now forms the genetic blueprint for the new individual. One of the 23 pairs of chromosomes are sex chromosomes, so gender is also determined at conception. 

Each egg carries an X chromosome and each sperm either an X or Y. If two X chromosomes combine, the baby will be a girl; if an X and Y chromosome combine, the baby will be a boy (see right).

Genetic inheritance means that successive generations can share certain characteristics. 

 What are genes?

Genes are located on rodlike structures called chromosomes that are found in the nucleus of every cell in the body. Each gene occupies a specific position on a chromosome. Because genes provide instructions for making proteins, and proteins determine the structure and function of each cell in the body, it follows that genes are responsible for all the characteristics you inherit. 

The full genetic instructions for each person, known as the human genome, is carried by 23 pairs of chromosomes, and consists of around 20,000–25,000 genes.

How inheritance works 

At conception, the embryo receives 23 chromosomes from the mother’s egg and 23 chromosomes from the father’s sperm. These pair up to make a total of 46 chromosomes. Pairs 1 to 22 are identical or nearly identical; the 23rd pair consist of the sex chromosomes, which are either X or Y. 

Each egg and sperm contains a different combination of genes. This is because when egg and sperm cells form, chromosomes join together and randomly exchange genes between each other before the cell divides. This means that, with the exception of identical twins, each person has unique characteristics

How gender is determined Of the 23 pairs of chromosomes that are inherited, one pair determines gender. This pair is composed either of two X (female) chromosomes, in which case the baby will be a girl, or of one X and one Y (male ) chromosome, in which case the baby will be a boy.

An egg always contains one X chromosome, while a sperm can carry an X or a Y chromosome. Whether your baby is a boy or a girl will therefore always be determined by the father. If a sperm carrying an X chromosome fertilizes the egg, the resulting embryo will be a girl. 

If a sperm with a Y chromosome fertilizes the egg, the resulting embryo will be a boy. In the male, both the X and Y chromosomes are active. In females, however one of the two X chromosomes is deactivated early in development of the embryo in order to prevent duplicate instructions. This could be the X chromosome from either the mother or the father.

Gene variations Each gene within a cell exists in two versions, one inherited from each parent. Often these genes are identical. However, some paired genes occur in slightly different versions, called alleles. There may be two to several hundred alleles of a gene, although each person can only have two. This variation in alleles accounts for the differences between individuals, such as color of eyes or shape of ears. One allele may be dominant and “overpower” the other recessive one (see box, right).

Why genetic disorders occur 

Genes usually exist in a healthy form, but somtimes a gene is faulty. Genetic disorders arise either when an abnormal gene is inherited or when a gene changes, or mutates. Genetic disorders may follow a dominant or recessive pattern of inheritance (see right). They can also be passed on via the X chromosome. 

Such sex-linked disorders are usually recessive, which means that a woman can carry the faulty gene without being affected, because she has another healthy X chromosome to compensate. If a boy receives an affected X chromosome, he will be affected; a girl will be a healthy carrier like her mother. An affected male could pass on the affected gene only to his daughters. 

YOU ARE 2 WEEKS AND 2 DAYS
264 days to go... 

WHAT’S HAPPENING INSIDE ?

Here a human egg cell 24 hours after fertilization is artificially colored purple. Around the egg is a thick layer (yellow) that has now become impenetrable. The two red areas, or pro-nuclei, contain genetic material from the mother and father before it has fused.

When your egg has been fertilized, hormonal changes naturally occur to stop your normal menstrual cycle.

At this early stage following fertilization of your egg, the developing embryo will signal its existence to the pituitary gland in your brain and switch off your menstrual cycle. It does this by producing a new hormone, called human chorionic gonadotrophin (hCG). This hormone overrides your usual monthly cycle and maintains the high progesterone levels that are essential for your pregnancy. The hormone progesterone is essential to an embryo’s survival in the uterus, and therefore to your baby’s well-being and development before birth. 

Later, starting around weeks four to five, your embryo will make all the hormones needed to maintain its own life. Of course its nourishment and shelter come from you, but even in the very early weeks of pregnancy the embryo behaves like an independent human, at least as far as its hormones and genes are concerned.

ASK A... DOCTOR 

I’ve been doing ovulation tests, but they’ve all been negative. Does this mean I haven’t ovulated this month? Even if you don’t appear to have ovulated this month, you may still have. It’s possible to miss the LH surge just by chance. This is more likely if you don’t test at the same time each day, or you drink a lot of water. 

Remember too that ovulation tests are imperfect, and it’s possible to get a false negative. If you had other symptoms of ovulation, such as pain, or changes in your mucus, it’s likely that you ovulated anyway. However if you have gone two or three months with consistently negative tests, then you might not be ovulating regularly. In that case, it’s worth seeking medical advice.

HEALTHY CONCEPTION 

When you’re trying to conceive, you’ll find you are much more aware of your general health. As a rule, colds, flu, and other common infections are unlikely to affect your fertility or your unborn baby if you have conceived. Some infections and viruses, however, can have a more serious impact: 

• Shingles and chickenpox (both caused by the same virus) are best avoided around the time of conception if you haven’t had chickenpox before. 

• Food poisoning, for example caused by listeria bacteria, can be harmful. 

• Toxoplasmosis can be contracted from handling cat feces.

AS A MATTER OF FACT

Too much testosterone can affect a woman’s fertility.

Small quantities of testosterone are secreted from the adrenal gland and the ovaries. In low levels it may aid fertility, but too much can affect the menstrual cycle and lead to infertility

 YOU ARE 2 WEEKS AND 3 DAYS 
263 days to go...

WHAT’S HAPPENING INSIDE? 

When the two nuclei have pooled their genetic material to create a cell containing its full complement of 46 chromosomes—23 each from the mother and father—the cell can start dividing, shown here at the first division creating a two-celled body

Vital cell divisions are now taking place as the fertilized egg begins its journey toward implantation.

The chromosomes from the sperm and egg joined over 24 hours ago. It takes around 30 hours for the resulting zygote to complete its first cell division. The zygote, at only 0.1 mm in diameter goes on to divide into 16 cells, forming a compact ball. 

Cell division is such that the ball of cells is hardly any larger than the  original zygote. The ball of 16 cells, now known as a “morula” (as it resembles a mulberry), travels toward the uterus, entering on day three after fertilization. Every cell within the morula is totipotent, meaning it is able to form any type of cell. From this point onward the cells will lose this function as they start to specialize.

FOCUS ON... IVF 

From eggs to embryos

Egg collection will be scheduled (see right), following the first stage of IVF. Not all follicles that were stimulated will contain eggs. Two days after egg retrieval, you will be given progesterone to thicken the uterus lining. Two to five days after fertilization, the most promising embryos are chosen to be transferred. If you’re under 40, you’ll have one or two embryos transferred. 

If you’re over 40, you may have up to three or more transferred. The goal is to achieve a pregnancy, yet limit the risks of a multiple pregnancy. Any leftover embryos can be frozen for future treatment cycles. Recent research suggests that frozen embryos are better than fresh ones—this may be because only the best embryos are selected for freezing and survive the freezing and thawing process. 

The outcome of IVF depends to a great extent on the woman’s age, but on average each cycle has a 20 percent success rate.

ASK A... DOCTOR 

I’ve been doing ovulation tests. I’ve now ovulated so do my partner and I need to keep having sex to make sure I conceive? You can’t be sure that you’ve conceived already, so the usual advice would be to continue lovemaking. Even if you’ve been tracking your ovulation by monitoring your temperature or cervical mucus, or by using an ovulation kit, you can’t be sure exactly when it occurred. It won’t be possible for you to pinpoint the exact time of ovulation. 

Since the fertile window is several days, you may as well continue having sex for at least a couple of days after what you think is your most fertile time. 

Furthermore, since sex says “I love you” more strongly than most other means of communication, it’s good for both you and your partner to stay intimate at times you’re not trying to conceive. 

Remember also that abstention doesn’t usually have the hopedfor effect of banking up and improving the quantity and quality of sperm. In fact, the opposite may happen.

 YOU ARE 2 WEEKS AND 4 DAYS 
262 days to go...

WHAT’S HAPPENING INSIDE? 

This is an embryo at the 16-cell stage, when it has changed from a zygote into a morula. It is in the process of dividing into a hollow ball of cells—the blastocyst—which will eventually implant in the lining of the uterus.

Significant changes are taking place daily within your uterus and within just 72 hours from now, the fertilized egg will implant.

Around four days following fertilization, fluid begins to collect within the morula. This creates a separate outer cell layer, one cell thick that encapsulates an inner mass of cells. The inner layer will become the embryo, and the outer layer the placenta. The whole structure now consists of approximately 58 cells and is termed the “blastocyst.” 

The blastocyst spends several days within the cavity of the uterus before implanting. The morula had an impenetrable outer surface as it traveled, but this disappears as the blastocyst prepares for implantation.

ASK A... MOM 

Why are people so interested in whether I’ve conceived? I certainly found that once I’d told people I was trying to have a baby, they were inordinately interested in the process. It was difficult, especially in the week when I was waiting to find out if I’d conceived. The best way to deal with it is to respond by saying that you’ll let people know if there’s news. If you’re struggling to conceive, telling people you’re having difficulties should help stop them from asking.

FOCUS ON... HEALTH 

Fertility: the alternative approach 

If you’re having difficulty conceiving, or just want to improve your chances, consider using a complementary therapy. Always inform the practitioner that you might be pregnant

Reflexology works by manipulating pressure points in the feet to improve energy flow to specific parts of the body. While there is plenty of anecdotal evidence that reflexology helps conception, this isn’t currently backed up by scientific research. However, it may help relieve stress, which can be a factor in couples who have problems conceiving. 

Acupuncture works on the principle that problems such as infertility are caused by blockages in the body’s energy flow or “qi.” By inserting tiny needles into energy points that are linked to the reproductive organs, the flow is restored. In 2008, after reviewing seven studies of more than 1,300 women having fertility treatment, researchers concluded that acupuncture given around the time of embryo transfer increases the chances of pregnancy. 

It’s not as clear whether acupuncture can improve fertility in couples not undergoing treatment, but it is thought to improve male fertility by improving sperm health and reducing stress, a factor that can impede the chances of conception. 

YOU ARE 2 WEEKS AND 5 DAYS 
261 days to go...

WHAT’S HAPPENING INSIDE?

This is an embryo at the blastocyst stage, five days after fertilization. It is seen hatching from the shell that originally surrounded the unfertilized egg. At this stage, the blastocyst has moved into the uterus and is preparing to implant.

While playing the waiting game, you may want to consider how you’d feel if there are two fertilized embryos waiting to implant!

Have you conceived, and might it be twins? Twins can be nonidentical or identical and each type of twins is conceived differently. 

Nonidentical (dizygotic) twins are the result of two separate eggs being fertilized by separate sperm. They may also occur as a result of IVF if two embryos are placed in the uterus. 

Identical (monozygotic) twins occur when a single egg is fertilized by a single sperm and divides into two embryos. This split can occur at any stage up to nine days after fertilization and its timing is critical to the way the placenta(s) and amniotic sac(s) are formed. If the zygote splits within the first three days, two separate placentas and amniotic sacs develop. If the split occurs at blastocyst stage (see opposite), four to nine days after fertilization, the fetuses will share a placenta but have separate sacs; when the split occurs after day nine, the fetuses will share a placenta and a sac. 

Having nonidentical (fraternal) twins, which come from two separate fertilized eggs, depends a lot on family history. It’s often said that twins skip a generation, which isn’t quite true. In fact, your chances of having twins are simply higher if you have a close relative with twins, but twins never become inevitable, however many members of your family have them. 

Family history is most relevant with nonidentical twins, and when the twins are on the mother’s side. This makes sense because this kind of twin relies on a woman releasing two eggs in any one cycle, which may be hereditary. However, for reasons that aren’t clear, a family history of twins on the father’s side can be important too. It may be that the male of the species can carry a gene which makes his daughter release more than one egg at a time when she ovulates.

The lining of the uterus, when fertilization occurs, becomes secretory to nourish an embryo. The lining prepares itself in the same way, no matter how many embryos implant. 

THE LOST TWIN 

Twin conceptions may be more common than they appear. Without knowing it, some women miscarry one twin in early pregnancy. It is sometimes possible to have symptoms of a miscarriage, yet, confusingly, the pregnancy then appears to continue until term, culminating in the birth of a completely normal singleton baby. 

Nobody is quite sure how often this happens, or why. While one in every 31 births in the US today is a twin birth, research using scans in very early pregnancy suggests that at conception the figure is much higher. Some experts believe that 15 percent of all births may start off as twins. Their loss could simply be nature’s way of dealing with imperfections. 

AS A MATTER OF FACT 

The odds of having identical twins are about 3.5 in 1000.

Some estimate that the chances of having twins after fertility-enhancing treatment is as high as 1 in 38.

YOU ARE 2 WEEKS AND 6 DAYS 
260 days to go...

WHAT’S HAPPENING INSIDE?

The blastocyst prepares to embed itself in the lining of the uterus—the endometrium. Once it is completely implanted—usually around seven days after fertilization— the pregnancy wlll become established.

Your reproductive organs undergo complex processes that will enable your body to maintain the pregnancy.  

 If you have conceived, the ball of cells known as the blastocyst that ` will eventually form the fetus will now be preparing to embed in the lining of your uterus, and the placenta will be starting to form.

 Before this happens, however, there is another important change going on. After you ovulate, the empty ovarian follicle develops into a structure called the corpus luteum (which means, literally, “yellow body”). This small, fluid-filled sac becomes increasingly “vascular,” developing blood vessels and beginning to produce the hormone progesterone. This is required to create mucus to allow your fertilized egg to survive, and build up the lining of your uterus, in which the blastocyst will soon imbed (see opposite). 

The corpus luteum also produces a little estrogen. By about 8–12 weeks of pregnancy, your placenta will take over the production of progesterone, but the corpus luteum continues to play a small role in hormone production until about six months, when it usually shrinks away.

THE MIRACLE OF CONCEPTION 

When you consider the multitude of events that have to fall neatly into place before a baby is conceived, it’s hard to believe that anyone can become pregnant. No wonder they talk about the miracle of life! 

To become pregnant the following have to happen: 

• Your hormone balance must be correct for the egg to develop. 
• Ovulation must take place: if you don’t release an egg, there is no way for fertilization to occur. 
• You need to have sex at the right time in your menstrual cycle; sperm can last about three days in healthy cervical mucus, but if your timing is off, egg and sperm are unlikely to meet. In some cases there may be only two or three days each month when you can conceive. 
• Your partner needs to produce plenty of good, healthy sperm that can penetrate your cervical mucus to reach the egg. 
• When the egg has been fertilized, the blastocyst has to implant securely in the lining of the uterus.
• The right levels of the hormone progesterone must be produced by the corpus luteum to maintain the pregnancy.

ASK A... DOCTOR

Should I stop taking medication in case I’ve conceived? Many medicines are safe to take, but some are not, or have not been fully evaluated. This last group includes many antihistamines for allergies, over-the-counter sleeping pills, and many analgesics. 

If you’ve accidentally taken an over-the-counter remedy that’s not considered appropriate for use in pregnancy, you’re unlikely to have done any harm with just one dose. However, seek medical advice if you’re concerned. 

If you need to continue using a medicine in pregnancy, ask if it’s safe to do so. While pharmacists are well-informed on all medicines, your doctor is the best person to consult on prescription-only drugs. 

YOU ARE 3 WEEKS EXACTLY 
259 days to go...

WHAT’S HAPPENING INSIDE? 

The blastocyst is firmly embedded in the lining of the uterus. Once this has happened, the placenta (the temporary organ that supplies the growing embryo with oxygen and nutrients) will begin to develop.

It’s a week since the egg was fertilized and it now implants in your uterus, where it will soon develop into an embryo.

Around seven days after fertilization, the blastocyst implants in the lining of the uterus. The outer cell layer, no longer protected, is able to attach to the lining of the uterus. The lining is now more receptive and has undergone changes that make it more “sticky” to aid attachment. The blastocyst erodes cells to sink beneath the surface. 

What was originally a single outer layer of cells now transforms into two layers. The outermost layer of cells creates space by eroding the lining, and it secretes hormones. These hormones inform your body that you’re pregnant and stimulate the uterus to support the pregnancy rather than shed its lining in what would normally be your period. The innermost cell layer will become the placenta and the amniotic sac that encloses the embryo. Within the blastocyst there is an inner cell mass that will form the embryo. 

STRETCH AND UNWIND 

It can help to relax in this interim period, before you do a pregnancy test. Fill some time by getting in shape with these simple stretches. Getting into the habit of doing these exercises now will help your body deal with the increased demands once you know you’re pregnant. Stretch before and after exercising to prevent muscle strain.

 

 

GO to The Fourth Week of Pregnancy from here