4 Weeks Pregnant: Implantation

Reviewed by Dr. Elisa Ross in June 2010

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Implantation occurs normally around the time when you'd be expecting your period, typically around the 4th week of pregnancy. This early stage of pregnancy can cause cramping and some spotting, but many moms-to-be feel no change (yet!) in their bodies.

During week four of your pregnancy (about five days after conception), implantation occurs. Once the embryo, now called a blastocyst, reaches the uterus, it searches for a nice place to implant. Then it burrows beneath the surface of the uterus and its cells begin to divide into two groups: those that form the placenta and those that form the baby.

Pregnancy Week 4: All About You

Dealing with Nausea: Here Comes Morning Sickness!
Nausea, better known as morning sickness, is one of the earliest—and probably most notorious—signs of pregnancy. Some women experience slight queasiness or none at all, while other sufferers are reduced to a diet of saltines and ginger ale.

Who Gets Morning Sickness
"Fifty to 90 percent of women have some degree of [morning sickness]," explains Miriam A. Erick, a registered dietitian at Brigham and Women's Hospital in Boston and the author of Managing Morning Sickness: A Survival Guide for Pregnant Women. She estimates up to 3.6 million women annually grapple with pregnancy-induced nausea.

How Long Nausea Lasts
The popular wisdom is that morning sickness ends with the first trimester, but Erick cites studies as well as experience with patients that point to nausea hanging on more often a few weeks into your second trimester.

Origins of Morning Sickness
Interestingly, researchers are still stumped as to the causes of morning sickness. "You would think that after centuries of morning sickness, we'd have an absolute answer," says Erick, "Not so!" Researchers have several prevailing theories—including that high hormone levels disrupt your body to the point of queasiness. Erick points out pregnant women's sensitivity to smells may play a part too.

Combating Nausea
To accommodate your more sensitive sniffer, avoid strong smells. Garlic, onions, fried meats, and heavily seasoned foods may throw you into dry heaves. And it's not just foods, advises Erick. Laundry soap, shower gels, perfume, cologne, diapers, dirty laundry, garbage cans, work place chemicals, and gas stations, can also trigger nausea. But you can't avoid every smell. Erick has a solution that's been working for her patients for years—lemon therapy. "I look at sniffing a lemon as putting a fence around your nose," says Erick. The lemon shields your nose from offensive, nausea-causing odors and may even have the side benefit of offering you some stress-relieving aromatherapy. If you're not a lemon fan, consider dousing a handkerchief or small washcloth with another scent that calms your nerves—and stomach. Pack a soothing scented lotion in your purse and rub some on your hands and neck for relief when you're on the go.

For battling nausea, there are plenty of pregnancy staples like saltines or graham crackers. What works for you depends on your own tastes. For some women, a protein boost from cheese or nuts staves off the queasies.

Your environment may also unsettle your stomach. Erick reports her patients suffer more when it's hot and humid or when it's cold and clammy.

When to Be Concerned
For most women, nausea is simply an unfortunate symptom of pregnancy, but if you experience vomiting around the clock, you may have something called hyperemesis gravidarum. Be sure to let your doctor know if your morning sickness is impeding your everyday life and preventing you from eating or drinking. You'll need to visit your doctor and make sure you're not at risk for dehydration or nutrition deficiencies.

Along with nausea, you may be feeling soreness as your body adjusts to all of the changes taking place. Expect your breasts and abdomen to be tender. You may also be taking more trips to the bathroom this week.