Pregnancy is the carrying of one or more embryos or fetuses by female mammals, including humans, inside their bodies. In a pregnancy, there can be multiple gestations (for example, in the case of twins, or triplets). Human pregnancy is the most studied of all mammalian pregnancies.
Human pregnancy lasts approximately 9 months between the time of the last menstrual cycle and childbirth (38 weeks from fertilisation). The medical term for a pregnant woman is genetalian, just as the medical term for the potential baby is embryo (early weeks) and then fetus (until birth).
A woman who is pregnant for the first time is known as a primigravida or gravida 1: a woman who has never been pregnant is known as a gravida 0; similarly, the terms para 0, para 1 and so on are used for the number of times a woman has given birth.
In many societies medical and legal definitions, human pregnancy is somewhat arbitrarily divided into three trimester periods, as a means to simplify reference to the different stages of fetal development.
The first trimester period carries the highest risk of miscarriage (natural death of embryo or fetus). During the second trimester the development of the fetus can start to be monitored and diagnosed. The third trimester marks the beginning of viability, which means the fetus might survive if an early birth occurs.
Before pregnancy begins, a female oocyte (egg) must join, by male spermatozoon in a process referred to in medicine as “fertilisation”, or commonly (though perhaps inaccurately) as “conception.”
In most cases, this occurs through the act of sexual intercourse, in which a man ejaculates inside a woman, thus releasing his sperm. Though pregnancy begins at implantation, it is often convenient to date from the first day of a woman’s last menstrual period. This is used to calculate the Estimated Date of Delivery (EDD).
Traditionally (according to Naegele’s rule, which is used to calculate the estimated date of delivery, or EDD), a human pregnancy is considered to last approximately 40 weeks (280 days) from the last menstrual period (LMP), or 37 weeks (259 days) from the date of fertilization. However, a pregnancy is considered to have reached term between 37 and 43 weeks from the beginning of the last menstruation.
Babies born before the 37 week mark are considered premature, while babies born after the 43 week mark are considered postmature.
According to Merck, the norm for human pregnancy is that it lasts 266 days from the date of fertilization. This is 38 weeks, or approximately 8 Gregorian months and 22.5 days, or 9.0 lunar months). Counting from the beginning of the woman’s last menstrual cycle, the norm is 40 weeks (the basis for Naegele’s rule).
According to the same reference, less 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. But it is not clear whether this refers to the due date calculated from an early sonograph or from the last menstruation (see further down).
Though these are the averages, the actual length pregnancy depends on various factors. For example, the first pregnancy tends to last longer than subsequent pregnancies.
An accurate date of fertilization 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 baby is perceived to be overdue. Due dates are only a rough estimate, and the process of accurately dating a pregnancy is complicated by the fact that not all women have 28 day menstrual cycles, or ovulate on the 14th day following their last menstrual period. Approximately 3.6% of all women deliver on the due date predicted by LMP, and 4.7% give birth on the day predicted by ultrasound.
The beginning of pregnancy may be detected in a number of ways, including various pregnancy tests which detect hormones generated by the newly-formed placenta. Clinical blood and urine tests can detect pregnancy soon after implantation, which is as early as 6-8 days after fertilization. Home pregnancy tests are personal urine tests, which normally cannot detect a pregnancy until at least 12-15 days after fertilization. Both clinical and home tests can only detect the state of pregnancy, and cannot detect its age.
In the post-implantation phase, the blastocyst secretes a hormone named human chorionic gonadotropin which in turn, 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 will swell in response to the blastocyst, and capillaries will be stimulated to grow in that region. This allows the blastocyst to receive vital nutrients from the woman. Pregnancy tests detect the presence of human chorionic gonadotropin.
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Prematurity is the most common cause of sickness and death among newborns. Babies born before the 37th week of pregnancy are often called preterm or “premature”, babies born before the 32nd week are considered very premature, babies born before the 28th week are considered extremely premature. Generally, babies born after the 25th week of pregnancy have a survival rate of between 50-60% (although they will stay an extended period of time in intensive care), which increases dramatically to over 90% after the 28th week.
Good advice is hard to come by as what’s considered good advice today may not be considered good years later. Take for example, Teflon, the biggest craze in the 70’s due to the non-sticking nature of the coating, replaced most all coating . Today, Teflon is looked down upon by some who say it is linked to cancer, thyroid disease, ulcerative colitis, and high cholesterol. That wonderful product that was raved about is now something to stay away from. That said, we’ve gathered a few things on a list for the expectant mom that are considered good tips for 2014!
Exercise is good in pregnancy and can lower the risk of miscarriage, so that’s really good news. It is said to reduce complications when in labor and even reduce the time of your labor, but don’t overdo it.
Start taking prenatal vitamins before you’re pregnant. Prenatal vitamins help nail and hair health even when not pregnant. I take them and I’m not expecting. In fact, some recommend prenatal vitamins after cancer treatments to help hair return faster and healthier. There you have it! I get mine from 
When cleaning around the house, opt for organic or natural cleaners instead of harsh ones or those full of chemicals and toxic ingredients. If you must use a chemical cleaner, be sure to wear rubber gloves as the toxins can penetrate your skin and enter the bloodstream and reach your baby. We found a great natural cleaner tips at 
If you have a cat, don’t change your cat litter. Have someone else do it for you. Coming into contact with the feces or urine of a cat may infect you with toxoplasmosis. One more chore off your list! From Wikipedia, “Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii.[1] The parasite infects most genera of warm-blooded animals, including humans, but the primary host is the felid (cat) family. ”
Do leg and foot stretches before heading to bed. I still remember the pain of waking up in the middle of the night with a horrible foot cramp that my husband could only fix if he grabbed my foot and pulled it up toward me. I didn’t know that you’re supposed to stretch before bedtime.
Lastly, be prepared to order a dinner while out and by the time the plate comes out from the kitchen, you’ve decided you want your husband’s meal instead. The funny thing is, I could never get away with this when not pregnant. But when pregnant, my husband would gladly give in knowing there was absolutely no rhyme or reason to it, nor could I change that craving.
