Pregnancy is when a female egg is fertilised by male sperm, creating an embryo or foetus which is then carried by the female inside her uterus, or womb. In any pregnancy, there can be more than one gestation, such as when a woman is having twins.
Pregnancy usually lasts for about 9 months between the time of the last menstrual period and childbirth which is roughly for a period of about 38 weeks from the moment the egg is fertilised.
The medical term for a pregnant woman is genetalian. The medical term for the growing baby in the early weeks of development is embryo.Later it is called a foetus, sometimes spelled fetus and finally at birth it is called a baby.
A woman who has never been pregnant is known as a gravida 0. The term used for a woman who is pregnant for the first time is primigravida or gravida 1.
Pregnancy is usually divided into three trimester periods. This is in order to make it easier to refer to the different stages of foetal development.The first trimester carries a high risk of miscarriage which is most usually a natural death of the embryo or foetus and it may lead to uncomfortable early pregnancy signs and cramping.
During the second trimester the growth of the foetus begins to be monitored. In the third trimester, the foetus is considered to have the ability to survive should it leave the womb prematurely, such as in an early birth.This is called the viability of the foetus.
Before pregnancy begins, a female oocyte, or egg, must be fertilized by a male spermatozoa.
Usually this will happen as a direct consequence of sexual intercourse, in which a man ejaculates inside a woman, releasing his sperm. A fertilized egg can also be implanted surgically or medically.Though pregnancy actually begins at the point of implantation, natural or otherwise, the start of the pregnancy is most often dated from the first day of a woman’s last menstruation. This is used to calculate the Estimated Date of Delivery or EDD. Pregnancy is calculated to last approximately 40 weeks from the last menstrual period. However, it can be anywhere between 37 and 43 weeks from the beginning of the last menstrual period. Babies born before 37 weeks are considered to be premature.
In fact less than 10% of births occur on the due date, while 50% tend to take place within a week of the due date, and almost 90% within two weeks. These are the averages. The actual length of a pregnancy that goes to full term depends on several factors. For example, the first pregnancy tends to last longer than any pregnancies after that. Knowing the exact date of fertilization is very useful, since it is used to calculate the results of various prenatal tests.
Cramping is normal in pregnancy, but towards the end of the term it may, of course, indicate that the baby is due to arrive. It may be decided to induce labour if a baby is thought to be overdue based on the calculated dates, so the more accurate these dates are the better. Due dates serve only as a rough estimate. The process of getting pregnancy dates correct is complicated by the fact that not all women have the same 28 day menstrual cycle. neither do they all ovulate on the 14th day following their last menstruation. In fact only about 3.5-4.5% of women actually deliver on the predicted due date.
The start of a pregnancy can be detected in various ways, such as pregnancy tests which work by detecting the hormonal changes generated by a newly-formed placenta. Urine tests or blood tests can also detect pregnancy soon after the egg has implanted, which can be as early as 1 week after fertilization. Home pregnancy tests work best after 2 weeks. Both clinical and home tests can tell if a woman is pregnant but cannot tell how long she has ben pregnant. After implantation, a hormone called human chorionic gonadotropin stimulates the woman’s ovary to continue producing progesterone. This helps to keep the lining of the uterus from shedding so that the embryo can continue to get nourishment.
It is at this time that the glands in the lining of the uterus start to swell and this is when some symptoms of cramping in early pregnancy may occur.
