Why does labor begin?

What starts labor is one of the great mysteries of medicine. "That's a Nobel prize-winning question," says Dr. Mark Taslimi, a professor of obstetrics and gynecology at Lucille Packard Children's Hospital in Palo Alto, California. One current theory is that stress hormones are released from the adrenal gland of the baby, which creates chemical changes in the placenta that cause the muscle of the uterus to develop involuntary contractions that turn into labor, he says. These regular, frequent contractions and the resulting opening of the cervix signal that labor has begun.

Still pregnant, plus more tests you may need

After months of anticipation, your due date rolls around, and you're still pregnant. It's a frustrating, but common, situation in which to find yourself. You may not be as late as you think, especially if you're relying solely on a due date calculated from the day of your last period because sometimes women ovulate later than expected. Even with reliable dating, some women have prolonged pregnancies for no apparent reason.

You still have a couple of weeks before you'll be considered "post-term." But to be sure your baby is still thriving; your practitioner will schedule you for testing to keep an eye on her if your pregnancy continues. You may have a biophysical profile (BPP), which consists of an ultrasound to look at your baby's overall movements, breathing movements (movement of her chest muscles and diaphragm), and muscle tone (whether she opens and closes her hand or extends and then flexes her limbs), as well as the amount of amniotic fluid that surrounds her (important because it's a reflection of how well the placenta is supporting your baby). Fetal heart rate monitoring (called a no stress test or NST) will generally be done as well — by itself or as part of the BPP. Or, you may have what's known as a modified BPP, which consists of an NST and an ultrasound to assess the amount of amniotic fluid. Whether you've started testing or not, it's important to keep track of your baby's movements and report any decrease in activity to your caregiver without delay.

40th Week Pregnancy

It's hard to say for sure how big your baby will be, but the average newborn weighs about 7 1/2 pounds (a small pumpkin) and is about 20 inches long. The biggest part of your baby's body is her head, but her still-pliable skull will give it the flexibility necessary to squeeze through the birth canal. Many parents are surprised by how long and sharp their newborn's nails are from the get-go.  Clipping them right away (ask a nurse for help) can prevent your baby from scratching her face.

Evening snacks that help you sleep

While it's true that gorging three hours or less before heading off to bed can cause heartburn and keep you up, a light bedtime snack can often help you get more shut-eye. What to try: foods that contain tryptophan — an amino acid with sleep-inducing properties — such as turkey, bananas, yogurt, eggs, meat, nuts, beans, fish, and cheese. "Warm beverages can also help get you ready for sleep and ease you into a relaxed state, provided they don't contain caffeine," says Nicole Britvan, a dietitian at Kaiser Permanente Outpatient Nutrition Clinic in San Francisco. Try warm milk (another food containing tryptophan) — a long-standing nighttime remedy.

Why do I feel a burst of energy?

Energetically scrubbing the bathroom, organizing the baby's room, or clearing away unwanted clutter in the house may be the modern manifestation of an evolutionary instinct to create a safe place for your baby to live, says Sherri Minelli, a childbirth educator in Encinitas, California. "The burst of energy before labor begins is a bit animalistic in nature," she says. "In today's world it translates to cleaning the house or making sure that your baby's room is finished.

While you're waiting plus how to handle anxiety about labor

At each of your now-weekly visits, your caregiver will do an abdominal exam to check your baby's growth and position. She might also do an internal exam to see whether your cervix has started ripening: softening, effacing (thinning out), and dilating (opening). But even armed with this information, there's still no way for your caregiver to predict exactly when your baby is coming. If you go past your due date, your caregiver will schedule you for fetal testing (usually a sonogram) after 40 weeks to ensure that it's safe to continue the pregnancy. If you don't go into labor on your own, most practitioners will induce labor when you're between one and two weeks overdue — or sooner if there's an indication that the risk of waiting is greater than the risks of delivering your baby without further delay.

39th Week Pregnancy

Your baby’s waiting to greet the world! He continues to build a layer of fat to help control his body temperature after birth, but it's likely he already measures about 20 inches and weighs a bit over 7 pounds, a mini watermelon. (Boys tend to be slightly heavier than girls.) The outer layers of his skin are sloughing off as new skin forms underneath.

What's the best way to prepare for life with a baby?

I think the key thing is to be flexible. Don't get caught up in a plan for how your life will be after the baby comes. In my experience, babies are very good at challenging the inner control freak in all of us. Develop a good social network and connect with other parents, both with kids the same age and with older kids since they've likely been through what you'll go through. I'd really encourage you to go on dates with your partner or friends. It's restorative to have some adult time and also to get some time for yourself. Find some friends, family, or sitters whom you trust with your child so you can have a few hours out. Besides that, put dimmer switches in the baby's room and God help you if you don't have a washing machine nearby.

The best preparation for life with a child is learning from your pregnancy that you're not always in control of every aspect of your life. Learn to be flexible and listen to your instincts. Babies don't expect us to know everything all at once. They grow up over time so we can learn as we go. Do enjoy the moments with your baby — they go so quickly. With my first child I was so scared all the time that I wasn't perfect, but I learned that perfection is not what our kids want from us. It's much more important to just be there to hold them, laugh with them, cry with them. They grow so quickly, but those moments are the ones you'll both remember for a lifetime.

Treat yourself

Use these last weeks (days?) before your baby arrives to do some things for yourself:

• Get a pedicure. It's too hard to cut your own toenails now anyway.

• Read a novel or go to the movies — these are two things you won't have time for after your baby's born.
• Go out for a leisurely dinner with your honey. Chances are you'll be eating take-out and quick home-cooked meals for a while after your baby's born.

The waiting game and why your water breaks

The next couple of weeks are a waiting game. Use this time to prepare your baby's nursery or to take care of tasks you may not get around to for a while after your baby's born. Take naps and catch up on your reading while you can.
Some swelling in your feed and ankles is normal in these last weeks, but call your practitioner without delay if you notice excessive or sudden swelling of your feet or ankles, more than slight swelling of your hands, any swelling in your face or puffiness around your eyes, or have a sudden weight gain. Also let her know immediately if you have severe or persistent headaches; visual changes (such as double or blurred vision, seeing spots or flashing lights, light sensitivity, or a temporary loss of vision), intense upper abdominal pain or tenderness, or nausea and vomiting because these are symptoms of a serious condition called preeclampsia.

38th Week Pregnancy

Your baby has really plumped up. She weighs between 6 and 7 1/2 pounds (boys tend to be slightly heavier than girls), and she's nearly 20 inches long. She has a firm grasp, which you'll soon be able to test when you hold her hand for the first time! Her organs have matured and are ready for life outside the womb. Wondering what color your baby's eyes will be? If she's born with brown eyes, they'll likely stay brown. If she's born with steel gray or dark blue eyes, they may stay gray or blue or turn green, hazel, or brown by the time she's 9 months old.

Expert Advice: Is it safe to have sex in the third trimester?

Yes, with a few exceptions. It's not safe if you're bleeding or have a placenta that's in front of the baby's head — they call this placenta previa. With placenta previa, if the penis comes in contact with the cervix or you have contractions as a result of orgasm, it can traumatize the placenta and cause significant enough bleeding that you lose the pregnancy. Also you shouldn't have sex if your membranes are ruptured (water breaks) because then the baby is no longer protected against any possible infection. It's also risky to have sex if it's early in your third trimester and you're having premature labor or you have a short cervix, because an orgasm can stimulate contractions. But if you're having a healthy normal pregnancy there's no risk, though as you get larger, it may be uncomfortable, requiring you to be creative about your position.

More Braxton Hicks contractions and increased vaginal discharge

It may be harder than ever to get comfortable enough to sleep well at night. Studies show that the quality of sleep in the third trimester is worse than any time before. (Once your baby is born, however, you may look back on this period rather fondly.)

Braxton Hicks contractions may be coming more frequently now and may last longer and be more uncomfortable. You might also notice an increase in vaginal discharge. If you see some "bloody show" (mucus tinged with a tiny amount of blood) in the toilet or in your undies, labor is probably a few days away — or less. (If you have heavier spotting or bleeding, call your caregiver immediately.)

In the last month of pregnancy, there's a higher probability of developing a serious condition called preeclampsia, which is one reason why your caregiver wants to see you more frequently now. She'll take your blood pressure to make sure it isn't too high and check your urine for excess protein — two key signs of preeclampsia. She'll also look for swelling — especially in your face and hands — and ask you about symptoms like headaches, upper abdominal pain, and vision changes. Another reason for weekly visits is to keep closer tabs on your baby to make sure he's doing okay. (If there are any concerns, you'll have a nonstress test or a biophysical profile.) The placenta slowly ages over the course of pregnancy and generally by 42 weeks it no longer efficiently eliminates wastes or delivers glucose to your baby, says Dr. Margaret Pfeifer, an obstetrician and gynecologist at the Mayo Clinic in Minnesota. If your caregiver feels your baby's at risk, she may recommend inducing labor.

37th Week Pregnancy

Congratulations! Your baby is full-term! This means that if your baby arrives now, his lungs should be fully mature and ready to adjust to life outside the womb, even though your due date is still three weeks away. He weighs a little over 6 pounds and measures between 19 and 20 inches. Many babies have a full head of hair at birth, with locks from 1/2 inch to 1 1/2 inches long.

Exercise to reduce back pain

Low back pain known as lumbar pain is common in late pregnancy. You feel it around your spine approximately at the level of, or a little above, your waist. Sitting or standing for long periods of time and lifting usually make it worse, and it tends to be more intense at the end of the day. To ease this kind of pain, try doing pelvic tilts, which stretch your muscles and, over time, strengthen them as well. Here's how:

• Get down on your hands and knees, arms shoulder-width apart and knees hip-width apart, keeping your arms straight.

• Tighten your abdominal muscles; tuck your buttocks under, and round your back, breathing in.

• Relax your back into a neutral position and breathe out.
• Repeat at your own pace.

Why do I suffer from heartburn?

During pregnancy, the placenta produces large amounts of the hormone progesterone, which relaxes the uterus. It has a similar effect on other smooth muscles, such as the intestines and the valve that usually keeps stomach acids out of the esophagus. Relaxation of this valve allows those acids to then make their way back up the digestive tract, resulting in the unpleasant burning sensation known as heartburn. As your baby and uterus get bigger, they push against your stomach, which can compound the problem. If you suffer from heartburn, you may not be able to eliminate it entirely, but there are steps you can take to minimize your discomfort.

What it feels like when your baby drops

You may have less heartburn and have easier time breathing when your baby starts to "drop" down into your pelvis. This process — called lightening — often happens a few weeks before labor if this is your first baby. (If you've given birth before, it probably won't happen before labor starts.) If your baby drops, you may also feel increased pressure in your lower abdomen, which may make walking increasingly uncomfortable, and you'll probably find that you have to urinate even more often than before. If your baby is very low, you may feel lots of vaginal pressure and discomfort as well. Some women say it feels as though they're carrying a bowling ball between their legs!

Feeling absent-minded? Forgetfulness is normal during the last trimester. You may be overwhelmed or just plain distracted by the huge life changes you're about to experience, as well as exhausted if you're having trouble getting a good night's sleep.

You might also notice that your Braxton Hicks contractions are more frequent now. Be sure to review the signs of labor with your practitioner and find out when she wants to hear from you. If you're full term, your pregnancy is uncomplicated, and your water hasn't broken, she'll probably have you wait to come in until you've been having contractions that last for about a minute each, coming every five minutes for an hour. Of course, you'll want to call right away if you notice a decrease in your baby's activity or think you're leaking amniotic fluid, or if you have any vaginal bleeding, fever, a severe or persistent headache, constant abdominal pain, or vision changes.

36th Week Pregnancy

Your baby is gaining about an ounce a day. She now weighs almost 6 pounds she now weighs almost 6 pounds and is a little under 19 inches long. She's shedding most of the downy hair that covered her body, as well as the vernix caseosa, the waxy substance that protected her skin during her nine-month amniotic bath. Next week, your baby will be considered full-term. Most likely she's in a head-down position, but if she isn't, your practitioner may suggest scheduling an external cephalic version, where she'll try to turn your baby by manipulating her from the outside of your belly.

Why do I feel like I'm waddling?

As you get closer to your due date, the cartilage and ligaments that join your pelvic bones increasingly soften and relax, causing an expansion that allows your baby to pass through the birth canal more easily. These changes cause some pregnant women to waddle, says Carolyn Sampselle, a professor of nursing at the University of Michigan. Lightening, when your baby descends lower into your pelvis prior to birth, can also cause the telltale waddle. Some women experience lightening several weeks before their babies arrive.

35th Week Pregnancy

Your baby doesn’t have much room to maneuver now that he's over 18 inches long and tips the scales at 5 pounds plus. Because it's so snug in your womb, he isn't likely to be doing somersaults anymore, but the number of times he kicks should remain about the same. His kidneys are fully developed now, and his liver can process some waste products. Most of his basic physical development is now complete — he'll spend the next few weeks putting on weight.