Pregnancy

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Wikipedia:Pregnancy




3D Ultrasound of a baby at 22 weeks

Pregnancy is the condition of a reproductive female having a developing embryo or fetus in the body, after the fertilization of an ovum by a sperm (1). Ultimately, pregnancy ends in labour.

Obstetrical visits

On the initial visit, women are asked to carry out the antenatal record, which constitutes a history and physical. Lab tests are also carried out, including the CBC, rubella vaccine, HIV test, pap smear, and a urine test.

On subsequent visits, the dates should be rechecked each visit. Symphysis-fundal height (SFH; in cm) should equal gestational age (GA) after 20 wks. Growth should also be plotted on a curve during the antenatal visits. The third Leopold maneuver is also used to determine the position of the baby. Blood pressure should also be monitored, and may be up to 140/90.

Fetal screening is also used to help assess the viability of the fetus.

Complications

Several complications can arise throughout pregnancy. In the first trimester, the two major potential problems are abortion and ectopic pregnancy.

Later in pregnancy, complications include gestational trophoblastic disease (GTD) and gestational choriocarcinoma.

First trimester bleeding

First trimester vaginal bleeding during the first 20 weeks occurs in nearly 25% of clinical pregnancies. It can be the result of a spontaneous abortion, molar pregnancy, or gestational choriocarcinoma. All patients experiencing bleeding in pregnancy whether or not it proceeds to abortion should receive RH immunoglobulin if the patient is RH negative.


Imaging

The purpose of first trimester imaging is to predict problems with the mother, confirm that a pregnancy is present inside the uterus, guess the gestational age, determine the number of fetuses and placentae, evaluate for an ectopic pregnancy and first trimester bleeding, and assess for early signs of anomalies.

Computerized tomography (CT) and X-rays are not used in first trimester imaging due to the ionizing radiation, which has teratogenic effects on the fetus. Instead, ultrasound is the imaging method of choice in the first trimester and throughout the pregnancy, since it emits no radiation, is portable, and allows for real-time imaging.

A normal gestation would reveal a gestational sac, yolk sac, and fetal pole. The gestational age can be assessed by evaluating the mean gestation sac diameter (MGD) before week 6, and the crown-rump length after week 6. Multiple gestation would be checked for by evaluating the number of placentae and amnionic sacs.

Anomalies are also sought in the first trimester by assessing nuchal translucency, nasal bone and anencephaly.

Maternal changes

During pregnancy, the mother undergoes many physiologic changes, be they cardiovascular, renal, hematologic, metabolic or respiratory, changes that become very important in the event of complications.

The mother is the sole provider of nourishment for her unborn baby, and so her plasma and blood volume increase by 40-50% to accomodate the changes. This results in overall vasodialation, increased heartrate (15 bpm), stroke volume, and cardiac output, ultimately increacing cardiac capacity by 70-80mL. Diastolic blood pressure consequently decreases between 12-26 weeks, and increases again to prepregnancy levels by 36 wks, beyond which physicians should look for preeclampsia.

Hematologically, the increase in plasma volume causes an increase in red blood cell mass. The mother also becomes hypercoagulable due to increased liver production of coagulation factors.

Pregnant women often have the sensation of shortness of breath. However, pregnant women oxygenate well, and maintain a total lung capacity comparable to non-pregnant women, with an increase in tidal, but a decrease in residual volume. Preggos breathe faster, and so have compensated respiratory alkylosis.

The increase in plasma volume results in increased levels of ACTH, ADH, aldosterone, and cortisol in the kidneys, ultimately increasing the glomerular filtration rate (GFR) by 50%, a change that subsides around 20 weeks postpartum. Pregnant women may also show more proteinuria (300mg/24 hrs) than non-pregnant women (150mg/24 hrs). While this is normal, if the number rises beyond the 300mg/24 hours threshold, this would suggest renal impairment.

Fully half of pregnant women will show signs of glucosuria, which is normal. If the glucosuria is persistant, gestational diabetes should be suspected.

Metabolism

During pregnancy, both protein metabolism and carbohydrate metabolism are affected. 1 kg of extra protein deposited, with half going to the fetus and placenta, and another half going to uterine contractile proteins, breast glandular tissue, plasma protein, and hemoglobin.

Carbohydrate metabolism also goes wonky. Pregnant women have lower fasting blood glucose, and progressive insulin resistance, mostly due to Human Placental Lactogen (HPL), which interferes with endogenous insulin use and peaks at 24-28 weeks.

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