Human pregnancy is the condition of carrying of one or more embryo(s) or fetus(es) within the female. Pregnancy can be multiple, with the records standing at eight ("octuplets"). However, in every case the majority of this babies, and sometimes all of them, Childbirth normally occurs about 38 weeks after fertilization, that is about 40 weeks from the beginning of the last menstruation. Thus, the usual "normal" pregnancy lasts about nine months. The first trimester
(first third) carries the highest risk of miscarriage. During the second trimester
, the development of the fetus can be more easily monitored and diagnosed. The beginning of the third trimester
often approximates the point of viability
, or the ability of the fetus to survive, with or without medical help, outside of the uterus.
The possibility of pregnancy occurs when the female The oocyte
(egg) is penetrated by the male spermatozoon
(sperm) which is termed fertilization
. The fusion of male and female gametes
(the generic name for egg and sperm) is designed by nature to occur through the act of sexual intercourse or, rarely, other non-penetrative sexual activity. The advent of artificial insemination has also made pregnancy possible without using natures design. Actual pregnancy begins at implantation
. Nevertheless, it is commonly dated from the first day of a woman's last menstrual period (LMP
), or from the date of conception if that date is known. Starting from one of these dates, the expected date of delivery (EDD
) can be calculated. Counting from the LMP, pregnancy usually lasts between 37 and 42 weeks, with the EDD at 40 weeks
, that is to say 38 weeks
after conception. 40 weeks is a little more than nine months and six days. Pregnancy is said to be at term when gestation
(the term used for the process which occurs after implantation) 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 pre-term
; from week 42 (294 days) events are considered post-term
. When a pregnancy exceeds 42 weeks (294 days), the risk of complications for mother and fetus increases significantly. In such a case, obstetricians usually prefer to induce labour, in an uncomplicated pregnancy, at some stage between 41 and 42 weeks. Though these are the averages, the actual length of pregnancy depends on various factors. The first pregnancy tends to last longer than subsequent pregnancies. Fewer than 10% of births occur on the due date; 50% of births are within a week of the due date, and almost 90% within two weeks.
- gravid - pregnant
- gravida - a pregnant female
- parity - the number of previous successful live births
- multigravida - a woman who has had more than one pregnancy
- multiparous - the condition of having had more than one pregnancy
- primigravida - a women in her first pregnancy
- nulliparous - never pregnant
...is used to identify the history of pregnancy, as follows in three examples:
- gravida 0, para 0 = nulliparous
- gravida 1, para 0 = during the first pregnancy
- gravida 3, para 2 = during the third pregnancy etc.
is in the first two months of development. At two months the embryo becomes a fetus
, which is to say that development in terms of organ formation is complete and now what is left is growth.
Signs of Pregnancy
- human chorionic gonadotropin (hCG) in the blood and urine
- missed menstrual period
- implantation bleeding that occurs at implantation of the embryo in the uterus during the third or fourth week after last menstrual period
- increased basal body temperature sustained for over two weeks after ovulation
- Chadwick's sign (darkening of the cervix, vagina, and vulva)
- Goodell's sign (softening of the vaginal portion of the cervix)
- Hegar's sign (softening of the Vaginal fornix), and Linea nigra, (darkening of the skin in a vertical line on the abdomen, caused by hyperpigmentation resulting from hormonal changes which usually appears around the middle of pregnancy).
Combinations of these signs are taken together to generate a suspicion of pregnancy. Actual diagnosis is achieved by pregnancy tests which detect hormones generated by the newly-formed placenta and found in the blood and urine as early as 6-8 days after fertilization. Home pregnancy tests are personal urine tests, which usually cannot detect a pregnancy until 12-15+ days after fertilization. Both clinical and home tests can only detect the state of pregnancy, but cannot define its length of duration. After implantation the blastocyst
(early embryonal stage) secretes human chorionic gonadotropin (hCG)
which stimulates the corpus luteum in the woman's ovary to continue producing progesterone. This acts to maintain the lining of the uterus so that the embryo will continue to be nourished. The glands in the lining of the uterus swell in response to the blastocyst, and capillaries are stimulated to grow in that region. This allows the blastocyst to receive vital nutrients from the mother. The hCG level typically rises to around 100,000 mIU/mL by 10 weeks of gestation. Another method of diagnosis is the sonogram can determine the age of the pregnancy fairly accurately.
Physiological Changes to Ensure a Proper Environment for the Fetus:
- Increases in blood sugar, breathing and cardiac output
- Progesterone and estrogens rise continually throughout pregnancy, stopping menstrual cycling
- The adrenal glands (cortisol and aldosterone) and ovaries of the mother and the placenta (which derives from the baby, not the mother) also produce many hormones
- Prolactin levels increase due to maternal pituitary gland enlargement by 50%, and brings about a change in the mammary gland presaging milk production
- Parathyroid hormone is increased and causes increased calcium uptake in the gut and decreased excretion of calcium by the kidney, thus supplying calcium needed to build the fetal skeleton
- Lactogen is produced by the placenta and stimulates lipolysis (breakdown of fat) and fatty acid metabolism by the mother (thus using lipds for energy in place of glucose), thus conserving blood glucose for use by the fetus. Lactogen also decreases maternal tissue sensitivity to insulin, and can lead to gestational diabetes
- 12-15 kilograms are gained during pregnancy due to fat deposition, growth of the reproductive organs and fetal tissues
- Blood volume increases by 40% in the first two trimesters
- Red blood cell numbers increase due to increased erythropoietin levels
- Heart rate increases as does stroke volume (aAfter pregnancy the change in stroke volume is not reversed)
- Cardiac output rises from 4 to 7 litres in the 2nd trimester
- Blood pressure fluctuates
- Renal plasma flow increases
Prenatal medical care is of recognized value throughout the developed world. Folic acid supplementation is the only type of supplementation of proven efficacy, although probably every vitamin is of benefit. After all, the very name "vitamin" indicates that it is required for life. A balanced, nutritious diet is an important aspect of a healthy pregnancy. Adequate periconceptional folic acid (also called folate or Vitamin B6) intake has been proven to limit fetal neural tube defects, preventing spina bifida, a very serious birth defect. Neural tube development occurs during the first 28 days of pregnancy and thus the necessity to guarantee adequate periconceptional folate intake. Folates (from folia, leaf) are abundant in spinach (fresh, frozen or canned), and are also found in green vegetables, salads, melon, hummus, and eggs. In the United States and Canada, most wheat products (flour, noodles) are fortified with folic acid. In my view, all females in child-bearing years should supplement with vitamin B6. In developed countries, such as Western Europe and the United States, Vitamin D and calcium, required for bone development, may require supplementation. Long-chain omega-3 (n-3) fatty acids have an effect on the developing fetus, and while further research is needed, to be on the safe side, this should also be supplemented in pregnancy but only in recommended amounts.
Careful washing of fruits and raw vegetables may remove listeria and tosoplasmosis, as may thoroughly cooking leftovers and meat. Soft cheeses may contain listeria, if milk is raw the risk may increase. Thus, avoid soft cheeses. Cat feces pose a particular risk of toxoplasmosis. Pregnant women are also more prone to catching salmonella infection from eggs and poultry, which therefore should be thoroughly cooked. Good hygiene in the kitchen can reduce these risks.
Proper Attitude Toward Weight Gain During Pregnancy
Caloric intake must be increased during pregnancy, to ensure proper development of the fetus, and therefore should not be cause for alarm. The amount of weight gained during pregnancy varies between women. Overall weight gain during the 9 month period for women who start pregnancy with normal weight should be 10 to 12 kilograms (22–26 lb). Insufficient weight gain can compromise the health of the fetus. Women with fears of weight gain or with eating disorders may choose to work with a therapist, to ensure that pregnancy does not trigger disordered eating. On the other hand, excessive weight gain can pose risks to the woman and the fetus. Women prone to being overweight may choose to plan a healthy diet and exercise plan to help moderate the amount of weight gained.
Preeclampsia occurs only during pregnancy and the postpartum period and affects both the mother and the unborn baby. It affects at least 5-8% of all pregnancies, is a rapidly progressive, and is characterized by high blood pressure and the presence of protein in the urine. Swelling, sudden weight gain, headaches and changes in vision are important symptoms, although some women with rapidly advancing disease report few symptoms. Preeclampsia tends to occur after 20 weeks gestation. Preeclampsia and other hypertensive disorders of pregnancy are a leading cause of maternal and infant illness and death. By conservative estimates, these disorders are responsible for 76,000 deaths world-wide each year.
Research on the immunological basis for pre-eclampsia indicates that continued exposure to a partner's semen has a strong protective effect against pre-eclampsia, largely due to the absorption of several immune modulating factors present in seminal fluid. This seems to be true for genital sex, and even more so for oral sex performed by the mother. Also, other studies have since investigated the strongly decreased incidence of pre-eclampsia in women who had received blood transfusions from their partner, The induction of allogeneic tolerance to the paternal HLA molecules of the fetus is apparently crucial. It is believed that pre-eclampsia is frequently caused by a failure of the mother's immune system to accept the fetus and placenta, which both contain "foreign" proteins from paternal genes. Regular exposure to the father's semen causes her immune system to develop tolerance to the paternal antigens.
Sexuality During Pregnancy
Most pregnant women can enjoy sexual intercourse throughout pregnancy. Most research suggests that, during pregnancy, both sexual desire and frequency of sexual relations decrease. Some studies indicate a second-trimester increase, preceding a decrease. However, these decreases are not universal: a significant number of women report greater sexual satisfaction throughout their pregnancies. Until the mid 20th century, it was commonly considered a taboo for pregnant women to engage in sexual activities.
Psychological research studies in the 1980s and '90s contend that it is useful for pregnant women to continue to have sexual activity, specifically noting that overall sexual satisfaction was correlated with feeling happy about being pregnant, feeling more attractive in late pregnancy than before pregnancy and experiencing orgasm. Despite common fears, during pregnancy, the baby is protected from the thrusting of sex by the amniotic fluid in the womb and by the woman's abdomen.