An egg can be fertilized for up to 24 hours after ovulation, and sperm can live for an average of 48 hours within the female reproductive tract. A woman with a 28-day menstrual cycle typically will ovulate on the 14th day of her cycle, give or take a day. However, cycles can be irregular and the exact time of ovulation usually is not known. Therefore, it is important to use contraception throughout the cycle if you are not planning on becoming pregnant.

About 5% of expectant mothers develop preeclampsia, also known as toxemia of pregnancy, which is marked by rising blood pressure, swelling of the hands and face, and protein in the urine. If you notice swelling or other signs of retaining fluid, such as weight gain, it is important to notify your doctor or midwife right away, but you shouldn't panic: Weight gain and some swelling of the feet and ankles are normal during pregnancy. Other symptoms of preeclampsia may include headache, nausea, abdominal pain and visual problems (blurred vision or seeing flashes of light like shooting stars). Preeclampsia can become a serious problem and can be associated with blood-clotting problems, liver dysfunction, and, in rare instances, the death of a mother or baby. Preeclampsia also can cause seizures or coma. If this happens, the condition is called eclampsia.

Twins may arise when ovulation and fertilization of two eggs occurs in one cycle, or when one fertilized egg splits into two embryos. In the former case, there will be two separate placentas (although if they grow next to one another, they may fuse and appear as one) and the twins will be fraternal (not identical). In the latter case, twins are identical and often the egg splits early enough that two placentas are formed; but sometimes, identical twins will share a placenta. In such cases there is a risk that the shared placenta will include connections between the circulations of the two twins and this can result in rare but serious complications (twin-to-twin transfusion syndrome). In the United States, the overall odds of having twins are one in 90, but the chance increases with age, or use of drugs to stimulate ovulation. Most twins that result from inducing ovulation or in vitro fertilization have separate placentas. Triplets occur in one of 7,500 pregnancies and quadruplets in one in 650,000 pregnancies.

While pregnancy is not a time to start a new strenuous sport, a brisk walk on a regular basis can be a good thing. The physical benefits of exercise can improve your stamina, flexibility and strength, and also make you look and feel better.

With advancing age, a mother's risk of Caesarean delivery increases. Factors contributing to this increase in older women include an increase of babies being in breech position (buttocks down), abnormalities in dilation of the cervix during labor, and more problems with the fetal heart rate (fetal distress) during labor. However, while the odds of having a Caesarean increase with age, older women still are more likely to have a vaginal delivery. In addition to an increased risk of Caesarean, age brings an increased risk of chromosomal problems (such as Down syndrome), medical complications of pregnancy (such as high blood pressure), twins, and other complications of labor and delivery (such as bleeding or placenta previa).

Another vitamin, folic acid, has been linked to the possible prevention of neural tube defects. It is recommended that all women planning pregnancy take a vitamin with 400 micrograms of folic acid. In special cases, a woman might need more amounts of this or other vitamins, as determined by her doctor. In fact, taking too much vitamin A (more than 10,000 units a day) can cause problems for a growing fetus.

While it is always a good thing to keep your skin well moisturized, neither cocoa butter nor any other cream actually will prevent stretch marks. Most women develop some stretch marks during pregnancy. Whether or not you will get stretch marks is determined by the genetically inherited resiliency of your skin. In other words, if your mother had stretch marks when she was pregnant, you are more likely to get them.

Only about 25 percent of women with asthma who become pregnant find that their symptoms get worse. About 25 percent actually report that their symptoms improve, while the other 50 percent report no change at all. Women with asthma usually can expect a normal pregnancy and delivery. Importantly, most medicines that are used to treat asthma are safe to use during pregnancy. In fact, there is greater risk to the baby of you not taking your asthma medications as directed by your doctor. Review all your medicines with your obstetrician or midwife at each visit.

Not any more. While this was true many years ago, today a woman with diabetes has excellent odds of a healthy outcome, both for herself and her baby. A visit with an obstetrician before getting pregnant provides an opportunity to address diabetes related issues prior to conception. This is especially true if the woman has uncontrolled blood sugars, high blood pressure or kidney problems.

The epidural block is an anesthesia that is injected through a catheter into the space between the dura matter (the sheath surrounding the spinal cord) and the bony vertebrae of your spine, numbing your body from the waist down. The medicine is injected next to the space containing the spinal fluid but not directly into the fluid itself. It is the spinal block that is anesthesia injected directly into the spinal fluid at the lower back.

About half of all women who experience bleeding during pregnancy go on to have normal deliveries and healthy babies. Bleeding happens in one of four pregnancies, typically during the first trimester. It is very important to report bleeding to your doctor immediately, for while it may turn out to be of no concern, it could be a sign of a serious problem such as an ectopic (tubal) pregnancy or a miscarriage.