This woman could be experiencing pre-term labor. A 20 week pregnancy is not considered viable. She should be seen immediately to determine if there is a cause such as cervical insufficiency (premature dilation of the cervix). 

Abruptio placentae is a serious condition where the placenta inappropriately and prematurely detaches from the uterus. Women with obstetric complications such as abruptio placentae can quickly develop disseminated intravascular coagulation (DIC). DIC is a clotting disorder in which the blood inappropriately clots. Severe bleeding can also occur as clotting proteins become scarce. Symptoms of DIC include blood clots, and bleeding into the tissues such as the skin and oral mucosa. A decreasing blood pressure is concerning due to the severe bleeding caused by the combination of DIC and abruptio placentae. Shortness of breath could indicate a the presence of a blood clot. Although uterine tenderness is of concern, it is common with abruptio placentae and does not indicate an immediately life-threatening condition.

The normal cervical canal is 2cm in length. Effacement is the thinning of the cervix as the body prepares for delivery. Thus, a 2cm cervix is 0% effaced and a 0cm cervix is 100% effaced.

If the placenta is not whole upon delivery, a piece may still be present in the uterus. This inhibits the ability of the uterus to shrink in size and may cause hemorrhage. The missing piece needs to be located immediately.

Marked fetal heart rate baseline variability of 25 beats per minute or more may be cause for concern. Similar findings may indicate that there is poor oxygenation of the fetus. Turn the mother to her left side (to increase perfusion) and notify the physician. Note that this is still in the normal range for fetal heart rate for a laboring patient (about 130 beats per minute), and that the low end of this spectrum is of slightly more concern.

Asian ethnicity is not considered a risk factor. Hispanic, Native American and African American ethnicities are considered risk factors for gestational diabetes. Others include maternal obesity, previous pregnancies with gestational diabetes, delivery of a very large baby, and a family history of diabetes.

The woman is experiencing the first stage labor and the second phase. The first stage of labor exists when the woman's cervix is dilating from 0-10cm. The second phase of the first stage occurs during dilation from 4-7cm and when the cervix is 40-80% effaced. The second stage of labor is when the cervix is dilated 10cm until the delivery of the baby. The third stage of labor is the delivery of the placenta. The first phase of labor is the onset of labor until the cervix is dilated 3cm. The third phase of labor is when the cervix fully dilates from 7cm to 10cm. 

During the third phase of the first stage of labor, the cervix dilates from 8-10 cm and effacement reaches 80-100%. The woman will be less able to focus on other things and may require more support from support persons. Labor may progress quickly and the nurse should be preparing for the second stage of labor, in which the cervix is fully dilated at 10cm. 

Polyphagia (excessive hunger), polydipsia (excessive thirst) and polyuria (excessive urination) are three hallmark signs that point to diabetes. While increased fatigue is common in pregnancy, combined with the other two symptoms, it may be concerning. Pre-eclampsia involves elevated blood pressure, swelling of the hands and feet, and protein in the urine. Toxoplasmosis results from infection by a parasite and can effect fetal development. A amniocentesis is performed to diagnose the infection of the fetus. Depending on the suspected duration of infection and the gestational age, drugs may be administered to decrease the chance of the parasite from infecting the fetus. Anemia, and parvovirus B19 are unlikely to cause all three of these symptoms occurring together.

All those listed may be asthma triggers with the exception of moist air. Typically, cold air may trigger asthma exacerbation. Additional triggers include exercise, respiratory illness, smoke, and mold.