Your pregnancy: 18 weeks

How your baby's growing:


Head to rump, your baby is about 5 1/2 inches long (about the length of a bell pepper) and he weighs almost 7 ounces. He's busy flexing his arms and legs — movements that you'll start noticing more and more in the weeks ahead. His blood vessels are visible through his thin skin, and his ears are now in their final position, although they're still standing out from his head a bit. A protective covering of myelin is beginning to form around his nerves, a process that will continue for a year after he's born. If you're having a girl, her uterus and fallopian tubes are formed and in place. If you're having a boy, his genitals are noticeable now, but he may hide them from you during an ultrasound
 
How your life's changing:


Hungry? An increase in appetite is pretty common about now. Make it count by choosing meals and snacks that are rich in nutrients instead of empty calories (chips, French fries, candy, and other sweets). Bigger, more comfortable clothes are a must now as your appetite and waistline grow.

Your cardiovascular system is undergoing dramatic changes, and during this trimester your blood pressure will probably be lower than usual. Don't spring up too fast from a lying or sitting position or you might feel a little dizzy.

From now on, when you do lie down, it's best to lie on your side — or at least partly tilted to one side. (When you lie flat on your back, your uterus can compress a major vein, leading to decreased blood return to your heart.) Try placing a pillow behind you or under your hip or upper leg for comfort.

If you haven't already had a second-trimester ultrasound, you'll probably have one soon. This painless procedure helps your practitioner check how your baby's growing, screen for certain birth defects, check the placenta and umbilical cord, determine whether the due date you're working with is accurate, and see how many babies you're carrying. During the exam, you might see your baby moving around or sucking his thumb. Bring your partner along, and be sure to ask for a printout for your baby's first photo album!

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Pregnancy-2

Progression

Stages in prenatal development, with weeks and months numbered by gestation.

Initiation

Pregnancy occurs as the result of the female gamete or oocyte merging with the male gamete, spermatozoon, in a process referred to, in medicine, as "fertilization", or more commonly known as "conception". After the point of "fertilization", it is referred to as an egg. The fusion of male and female gametes usually occurs through the act of sexual intercourse, resulting in spontaneous pregnancy. However, the advent of artificial insemination and in vitro fertilisation have also made achieving pregnancy possible in cases where sexual intercourse does not result in fertilization (e.g., through choice or male/female infertility).

Perinatal period

Perinatal defines the period occurring "around the time of birth", specifically from 22 completed weeks (154 days) of gestation (the time when birth weight is normally 500 g) to 7 completed days after birth.

Legal regulations in different countries include gestation age beginning from 16 to 22 weeks (5 months) before birth.

Postnatal period

Main article: Postnatal

The postnatal period begins immediately after the birth of a child and then extends for about six weeks. During this period the mother's body returns to prepregnancy conditions as far as uterus size and hormone levels are concerned.

Duration

The expected date of delivery (EDD) is 40 weeks counting from the last menstrual period (LMP), and birth usually occurs between 37 and 42 weeks. The actual pregnancy duration is typically 38 weeks after conception. Though pregnancy begins at conception, it is more convenient to date from the first day of a woman's last menstrual period, or from the date of conception if known. Starting from one of these dates, the expected date of delivery can be calculated. Forty weeks is 9 months and 6 days, which forms the basis of Naegele's rule for estimating date of delivery. More accurate and sophisticated algorithms take into account other variables, such as whether this is the first or subsequent child (i.e., pregnant woman is a primip or a multip, respectively), ethnicity, parental age, length of menstrual cycle, and menstrual regularity.

Pregnancy is considered "at term" when gestation attains 37 complete weeks but is less than 42 (between 259 and 294 days since LMP). Events before completion of 37 weeks (259 days) are considered preterm; from week 42 (294 days) events are considered postterm. When a pregnancy exceeds 42 weeks (294 days), the risk of complications for woman and fetus increases significantly. As such, obstetricians usually prefer to induce labour, in an uncomplicated pregnancy, at some stage between 41 and 42 weeks.

Recent medical literature prefers the terminology preterm and postterm to premature and postmature. Preterm and postterm are unambiguously defined as above, whereas premature and postmature have historical meaning and relate more to the infant's size and state of development rather than to the stage of pregnancy.

Fewer than 5% of births occur on the due date; 50% of births are within a week of the due date, and almost 90% within 2 weeks. It is much more useful, therefore, to consider a range of due dates, rather than one specific day, with some online due date calculators providing this information.

Accurate dating of pregnancy is important, because it is used in calculating the results of various prenatal tests (for example, in the triple test). A decision may be made to induce labour if a fetus is perceived to be overdue. Furthermore, if LMP and ultrasound dating predict different respective due dates, with the latter being later, this might signify slowed fetal growth and therefore require closer review.

The Age of Viability has been receding relentlessly as medical revolution continues to unfold. Whereas it used to be 28 weeks, it has been brought back to as early as 23, or even 22 weeks in some countries. Unfortunately, there has been a profound increase in morbidity and mortality associated with the increased survival to the extent it has led some to question the ethics and morality of resuscitating at the edge of viability.[citation needed]

Pregnancy Test

History

Jan Steen's The Doctor's Visit. Included in this 17th century painting is a depiction of a dubious pregnancy test: a ribbon dipped in the patient's urine and then burned. Records of attempts at pregnancy testing have been found as far back as the ancient Greek and ancient Egyptian cultures. The ancient Egyptians watered bags of wheat and barley with the urine of a possibly pregnant woman. Germination indicated pregnancy. The type of grain that sprouted was taken as an indicator of the fetus's sex. Hippocrates suggested that a woman who had missed her period should drink a solution of honey in water at bedtime: resulting abdominal distention and cramps would indicate the presence of a pregnancy. Avicenna and many physicians after him in the Middle Ages performed uroscopy, a nonscientific method to evaluate urine.

Selmar Aschheim and Bernhard Zondek introduced testing based on the presence of human chorionic gonadotropin (hCG) in 1928. Early studies of hCG had concluded that it was produced by the pituitary gland. In the 1930s, Georgeanna Jones discovered that hCG was produced not by the pituitary gland, but by the placenta. This discovery was important in relying on hCG as an early marker of pregnancy. In the Aschheim and Zondek test, an infantile female mouse was injected subcutaneously with urine of the person to be tested, and the mouse later was killed and dissected. Presence of ovulation indicated that the urine contained hCG and meant that the person was pregnant. A similar test was developed using immature rabbits. Here, too, killing the animal to check her ovaries was necessary. An improvement arrived with the frog test, introduced by Lancelot Hogben, which still was used in the 1950s and allowed the frog to remain alive and be used repeatedly: a female frog was injected with serum or urine of the patient; if the frog produced eggs within the next 24 hours, the test was positive. This was called the Bufo test, named after the toad genus Bufo, which was originally used for the test. Other species of toads and frogs have been used later on.

Direct measurement of antigens, such as hCG, was made possible with the invention of the radioimmunoassay in 1959, . Radioimmunoassays require sophisticated apparatus and special radiation precautions and are expensive. In the 1970s, the discovery of monoclonal antibodies led to the development of the relatively simple and cheap immunoassays, such as agglutination-inhibition-based assays and sandwich ELISA, used in modern home pregnancy tests.

Modern tests

The test for pregnancy which can give the quickest result after fertilisation is a rosette inhibition assay for early pregnancy factor (EPF). EPF can be detected in blood within 48 hours of fertilization. However, testing for EPF is expensive and time-consuming.

Most chemical tests for pregnancy look for the presence of the beta subunit of hCG or human chorionic gonadotropin in the blood or urine. hCG can be detected in urine or blood after implantation, which occurs six to twelve days after fertilization. Quantitative blood (serum beta) tests can detect hCG levels as low as 1 mIU/mL, while urine tests have published detection thresholds of 20 mIU/mL to 100 mIU/mL, depending on the brand. Qualitative blood tests generally have a threshold of 25 mIU/mL, and so are less sensitive than some available home pregnancy tests. Most home pregnancy tests are based on lateral-flow technology.

With obstetric ultrasonography the gestational sac sometimes can be visualized as early as four and a half weeks of gestation (approximately two and a half weeks after ovulation) and the yolk sac at about five weeks' gestation. The embryo can be observed and measured by about five and a half weeks. The heartbeat may be seen as early as six weeks, and is usually visible by seven weeks' gestation.

Accuracy

Negative pregnancy test, human subject.A systematic review published in 1998 showed that home pregnancy test kits, when used by experienced technicians, are almost as accurate as professional laboratory testing (97.4%). When used by consumers, however, the accuracy fell to 75%: the review authors noted that many users misunderstood or failed to follow the instructions included in the kits. Improper usage may cause both false negatives and false positives.

Timing of test

False negative readings can occur when testing is done too early. Quantitative blood tests and the most sensitive urine tests usually detect hCG shortly after implantation, which can occur anywhere from 6 to 12 days after ovulation. Less sensitive urine tests and qualitative blood tests may not detect pregnancy until three or four days after implantation. Menstruation occurs on average 14 days after ovulation, so the likelihood of a false negative is low once a menstrual period is late.

Ovulation may not occur at a predictable time in the menstrual cycle, however. A number of factors may cause an unexpectedly early or late ovulation, even for women with a history of regular menstrual cycles. Using ovulation predictor kits (OPKs), or charting the fertility signs of cervical mucus or basal body temperature give a more accurate idea of when to test than day-counting alone.

The accuracy of a pregnancy test is most closely related to the day of ovulation, not of the act of intercourse or insemination that caused the pregnancy. It is normal for sperm to live up to five days[11] in the fallopian tubes, waiting for ovulation to occur.[12] It could take up to twelve further days for implantation to occur, meaning even the most sensitive pregnancy tests may give false negatives up to seventeen days after the act that caused the pregnancy. Because some home pregnancy tests have high hCG detection thresholds (up to 100 mIU/mL), it may take an additional three or four days for hCG to rise to levels detectable by these tests — meaning false negatives may occur up to three weeks after the act of intercourse or insemination that causes pregnancy.

False positives

False positive test results may occur for several reasons. These include: errors of test application, use of drugs containing the assay molecule, and non-pregnant production of the assay molecule.

Spurious evaporation lines may appear on many home pregnancy tests if read after the suggested 3–5 minute window or reaction time, independent of an actual pregnancy. False positives may also appear on tests used past their expiration date.

A woman who has been given an hCG injection as part of infertility treatment will test positive on pregnancy tests that assay hCG, regardless of her actual pregnancy status. However, some infertility drugs (e.g., clomid) do not contain the hCG hormone.[13]

Some diseases of the liver, cancers, and other medical conditions may produce elevated hCG and thus cause a false positive pregnancy test. These include choriocarcinoma and other germ cell tumors, IgA deficiencies, heterophile antibodies, enterocystoplasties, gestational trophoblastic diseases (GTD), and gestational trophoblastic neoplasms (GTN).

Viability

Pregnancy tests may be used to determine the viability of a pregnancy. Serial quantitative blood tests may be done, usually 2–3 days apart. Below an hCG level of 1,200 mIU/ml the hCG usually doubles every 48–72 hours, though a rise of 50–60% is still considered normal. Between 1,200 and 6,000 mIU/ml serum the hCG usually takes 72–96 hours to double, and above 6,000 mIU/ml, the hCG often takes more than four days to double. Failure to increase normally may indicate an increased risk of miscarriage or a possible ectopic pregnancy.

Ultrasound is also a common tool for determining viability. A lower than expected heart rate or missed development milestones may indicate a problem with the pregnancy.[9] Diagnosis should not be made from a single ultrasound, however. Inaccurate estimations of fetal age and inaccuracies inherent in ultrasonic examination may cause a scan to be interpreted negatively. If results from the first ultrasound scan indicate a problem, repeating the scan 7–10 days later is reasonable practice.

Get ready for the big time

Pre-pregnancy nutritional status has a very close relationship with the health of the newborn. Good pre-pregnancy health condition brings healthy and lively newborns, with very few perinatal illness, and even has positive impact on babies’ intelligence development.

During pregnancy, baby lives in the mother's womb for about 40 weeks. The fertilized egg grows and develops finally into a handsome lovely baby who has independent organs and weights about 3200 grams.

Fetus stage is the fastest growing and developing period in a people’s whole life. Of course, this stage needs a lot of nutrients which directly come from the mother. In order to ensure fetus's healthy growth, new mommies must ensure that the uterus, placenta, amniotic fluid and breast areas are all healthy and ready for the new arrivals. Therefore, pregnant women, from preparation of pregnancy, you need to add extra nutrition. If the nutritional intake of pregnant women is inadequate, fetus won’t have adequate nutrition as well.

If you want to get pregnant, according to your personal physical situation, you need to have pre-pregnancy diet as soon as possible. Don’t wait until it is too late to all. Everyone is different. Therefore, before you take any supplements, do consult your GP or nutrition consultants. Choose the best method and have the appropriate dose based on your own condition.

In general, ordinary women need to start special diet and have supplements 3 months to half a year before pregnancy. Their daily meal need to content quality protein, vitamins, minerals, trace elements and certain amount of fat. These nutrients are the material basis of fetal growth and development.

High quality protein is easily digested and absorbed, such as chickens, ducks, fish, lean meat, shrimp, eggs, tofu, soy products, etc. Vitamin with A, D, C, B are essential. Fresh vegetables and fruits are rich in vitamins, minerals and trace elements, including calcium, iron, phosphorus, zinc, iodine. Calcium and phosphorus are the keys of fetal bone and teeth developing. Iron is important on hematopoietic function. Zinc and iodine are good for mental development and prevention of fetal malformations. Milk, eggs, bones, animal liver, dried small shrimps, aquatic product and nuts contain such substances. Moderate intake of fat can help the absorption and utilization of soluble vitamins.

For those who are in frail physique and poor nutritional status. The pre-pregnancy diet is extremely important. The diet preferably is started a year before pregnancy. In addition to intake adequate nutrition, they should also know that nutrition must be comprehensive, not partial eclipse. Do not be picky eaters, balance your food. But remember all these should be gradual and don’t be too ambitious.

For those who are in good nutritional status and have appropriate amount of body fat, in general, no need to increase in nutrition. However, have high-quality protein, vitamins, minerals, trace elements intake is still essential. Remember, consume less foods that are high in fat and sugar.