Pregnancy also is known as gestation, is the time during which one or more offspring develops inside a woman. A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse but can occur through assisted reproductive technology procedures. A pregnancy may end in a live birth, a spontaneous miscarriage, an induced abortion, or a stillbirth. Childbirth typically occurs around 40 weeks from the start of the last menstrual period (LMP). This is just over nine months – (gestational age) where each month averages 31 days.[rx][rx] When using fertilization age it is about 38 weeks.[rx] An embryo is the developing offspring during the first eight weeks following fertilization, (ten weeks gestational age) after which, the term fetus is used until birth.[rx]
Symptoms Of Pregnancy
Nausea and Vomiting
Nausea and vomiting may come as early as a week into the pregnancy. Many women experience illness in the morning (morning sickness), some in the afternoon or evening, others feel nausea throughout the entire day. There is no explanation as to why pregnant women feel this or even a solution as to how to prevent it – however, eating small frequent meals, and snacking on saltine crackers seems to give some kind of relief. Eating a protein/carbo-hydrate at bedtime (try an apple and a glass of milk) tends to lessen the nausea that occurs in the morning.
Breasts may be very tender, swollen and start to enlarge. Many times the veins within the breast will become more visible. Your nipples may start to darken in color, become more erect and be extremely sensitive. These symptoms are due to increasing amount of HCG hormone that begins at implantation.
Pregnancy causes the uterus to swell and it will start to enlarge for the growing fetus immediately. The uterus puts pressure on your bladder making you feel the need for more frequent urination. Many women start to feel this symptom within a week or two after pregnancy has occurred.
Feeling Tired / Sluggish
This one is pretty obvious. When pregnant your body is going through some major hormonal changes. HCG levels alone go from 0 – 250,000 mIU/ml in just twelve weeks. Your temperature is also higher due to the amount progesterone circulating through your body which will also make you feel a little sluggish.
Missed Period / Light Bleeding
Light bleeding (spotting) may occur approximately 8 – 10 days from ovulation. It usually happens around the same time you would have gotten your menstrual period. Some women assume they have started their period when in fact they are pregnant. The spotting is caused from implantation which is when the fertilized egg burrows into the endometrial lining.
Dizziness and/or Fainting
When standing in one place you may feel dizzy or even faint. The growing uterus compresses major arteries in your legs which causes your blood pressure to drop making you extremely lightheaded. Skipping meals or going too long without eating may cause you to feel dizzy or faint. When not eating frequently enough it causes low blood sugar. Blood sugar is the primary source of food for your baby so it will be depleted much more quickly.
Pregnancy hormones will slow down bowel functions to give maximum absorption time of vitamins and nutrients. Unfortunately, this symptom usually only gets worse as the pregnancy progresses.
Raging hormones are the cause of this…along with having to put up with all the other symptoms. This symptom should decrease soon into the second trimester but until then, a healthy diet, moderate exercise, and plenty of sleep should help the crabbiness somewhat.
The uterus is very swollen and starts to push upward as it grows. The increasing levels of HCG will also slow down digestion making your stomach not empty as fast which increases the stomach acid.
Common symptoms and discomforts of pregnancy include:
- Morning sickness
- Pelvic girdle pain
- Back pain
- Braxton Hicks contractions. Occasional, irregular, and often painless contractions that occur several times per day.
- Peripheral edema swelling of the lower limbs. A common complaint in advancing pregnancy. Can be caused by inferior vena cava syndrome resulting from compression of the inferior vena cava and pelvic veins by the uterus leading to increased hydrostatic pressure in lower extremities.
- Low blood pressure often caused by compression of both the inferior vena cava and the abdominal aorta (aortocaval compression syndrome).
- Increased urinary frequency. A common complaint, caused by increased intravascular volume, elevated glomerular filtration rate, and compression of the bladder by the expanding uterus.
- Urinary tract infection[rx]
- Varicose veins. Common complaints caused by relaxation of the venous smooth muscle and increased intravascular pressure.
- Hemorrhoids (piles). Swollen veins at or inside the anal area. Caused by impaired venous return, straining associated with constipation, or increased intra-abdominal pressure in later pregnancy.[rx]
- Regurgitation, heartburn, and nausea.
- Stretch marks
- Breast tenderness is common during the first trimester and is more common in women who are pregnant at a young age.
- Melasma, also known as the mask of pregnancy, is a discoloration, most often of the face. It usually begins to fade several months after giving birth.
Start of gestational age
The American Congress of Obstetricians and Gynecologists recommend the following methods to calculate gestational age
- Directly calculating the days since the beginning of the last menstrual period.
- Early obstetric ultrasound, comparing the size of an embryo or fetus to that of a reference group of pregnancies of known gestational age (such as calculated from last menstrual periods), and using the mean gestational age of other embryos or fetuses of the same size. If the gestational age as calculated from an early ultrasound is contradictory to the one calculated directly from the last menstrual period, it is still the one from the early ultrasound that is used for the rest of the pregnancy.[rx]
- In case of in vitro fertilization, calculating days since oocyte retrieval or co-incubation and adding 14 days.[rx]
Pregnancy is divided into three trimesters, each lasting for approximately 3 months.[rx] The exact length of each trimester can vary between sources.
- The first trimester – begins with the start of gestational age as described above, that is, the beginning of week 1, or 0 weeks + 0 days of gestational age (GA). It ends at week 12 (11 weeks + 6 days of GA)[rx] or end of week 14 (13 weeks + 6 days of GA).[rx]
- The second trimester – is defined as starting, between the beginning of week 13 (12 weeks +0 days of GA)[rx] and the beginning of week 15 (14 weeks + 0 days of GA).[rx] It ends at the end of week 27 (26 weeks + 6 days of GA)[rx] or end of week 28 (27 weeks + 6 days of GA).[rx]
- The third trimester – is defined as starting, between the beginning of week 28 (27 weeks + 0 days of GA)[rx] or the beginning of week 29 (28 weeks + 0 days of GA).[rx] It lasts until childbirth.
Estimation of the due date
Due date estimation basically follows two steps:
- Determination of which time point is to be used as origin for gestational age, as described in the section above.
- Adding the estimated gestational age at childbirth to the above time point. Childbirth on average occurs at a gestational age of 280 days (40 weeks), which is therefore often used as a standard estimation for individual pregnancies.[rx] However, alternative durations as well as more individualized methods have also been suggested.
Naegele’s rule is a standard way of calculating the due date for a pregnancy when assuming a gestational age of 280 days at childbirth. The rule estimates the expected date of delivery (EDD) by adding a year, subtracting three months, and adding seven days to the origin of gestational age. Alternatively, there are mobile apps, which essentially always give consistent estimations compared
General Risk Factors of Pregnancy
Factors increasing the risk (to either the pregnant individual, the fetus/es, or both) of pregnancy complications beyond the normal level of risk may be present in the pregnant individual’s medical profile either before they become pregnant or during the pregnancy.[rx] These pre-existing factors may related to the individual’s genetics, physical or mental health, their environment and social issues, or a combination of those.[rx]
Some common biological risk factors include:
- Age of either parent
- Adolescent parents
- Older parents
- individuals are at an increased risk of complications during pregnancy and childbirth as they age. Complications for those 45 or older include increased risk of primary Caesarean delivery (i.e. C-section).
- Height – Pregnancy in individuals whose height is less than 1.5 meters (5 feet) correlates with higher incidences of preterm birth and underweight babies. Also, these individuals are more likely to have a small pelvis, which can result in such complications during childbirth as shoulder dystocia.[rx]
- Low weight: individuals whose pre-pregnancy weight is less than 45.5 kilograms (100 pounds) are more likely to have underweight babies.
- Obese individuals are more likely to have very large babies, potentially increasing difficulties in childbirth. Obesity also increases the chances of developing gestational diabetes, high blood pressure, preeclampsia, experiencing post-term pregnancy and requiring a cesarean delivery.[rx]
- Pre-existing disease in pregnancy, or an acquired disease – A disease and condition not necessarily directly caused by the pregnancy, such as diabetes mellitus in pregnancy, lupus in pregnancy or thyroid disease in pregnancy.
- Risks arising from previous pregnancies
- Complications experienced during a previous pregnancy are more likely to recur.[rx][rx]
- Many previous pregnancies: individuals who have had five previous pregnancies face increased risks of very rapid labor and excessive bleeding after delivery.
- Multiple previous fetuses: individuals who have had more than one fetus in a previous pregnancy face increased risk of the mislocated placenta.[rx]
- Multiple pregnancies – Having more than one fetus in a single pregnancy.
Some common environmental risk factors include:
- Exposure to environmental toxins in pregnancy
- Exposure to recreational drugs in pregnancy
- Ethanol during pregnancy can cause fetal alcohol syndrome and fetal alcohol spectrum disorder.
- Tobacco smoking and pregnancy, when combined, causes twice the risk of premature rupture of membranes, placental abruption and placenta previa.[rx] Also, it causes 30% higher odds of the baby being born prematurely.[rx]
- Prenatal cocaine exposure is associated with, for example, premature birth, birth defects and attention deficit disorder.
- Prenatal methamphetamine exposure can cause premature birth and congenital abnormalities.[rx] Other investigations have revealed short-term neonatal outcomes to include small deficits in infant neurobehavioral function and growth restriction when compared to control infants.[rx] Also, prenatal methamphetamine use is believed to have long-term effects in terms of brain development, which may last for many years.[rx]
- Cannabis in pregnancy is possibly associated with adverse effects on the child later in life.
- Ionizing radiation[rx]
- Social and socioeconomic factors – Generally speaking, unmarried individuals and those in lower socioeconomic groups experience an increased level of risk in pregnancy, due at least in part to lack of access to appropriate prenatal care.[rx]
- Unintended pregnancy – Unintended pregnancies preclude preconception care and delays prenatal care. They preclude other preventive care, may disrupt life plans and on average have worse health and psychological outcomes for the mother and, if birth occurs, the child.[rx][rx]
- Exposure to pharmaceutical drugs in pregnancy – [rx] Anti-depressants, for example, may increase risks of such outcomes as preterm delivery.[rx]
Some disorders and conditions can mean that pregnancy is considered high-risk (about 6-8% of pregnancies in the USA) and in extreme cases may be contraindicated. High-risk pregnancies are the main focus of doctors specialising in maternal-fetal medicine.
Serious pre-existing disorders which can reduce a woman’s physical ability to survive pregnancy include a range of congenital defects (that is, conditions with which the woman herself was born, for example, those of the heart or reproductive organs, some of which are listed above) and diseases acquired at any time during the woman’s life.