Pregnancy Trimesters: What to Expect

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Milestones During Pregnancy First Trimester Second Trimester Third Trimester Post Pregnancy

Milestones During Pregnancy

For obstetricians, three is certainly a magic number. We tend to think of pregnancy in trimesters, each composed of about 13 weeks. A lot happens in each trimester, and here I’ll outline what is occurring and what you might notice, during each of these phases.

First Trimester

During the first three months of pregnancy, the baby's basic organ system starts to develop. During this time, some women experience nausea, which usually subsides at the end of the first trimester. Don't be afraid to speak with your midwife or doctor about remedy options that might be a fit for you. Starting around three weeks into pregnancy, many women feel tired (as I tell my patients, some folks talk about eating for two – I talk about sleeping for two), but this fatigue should start to fade around weeks seven or eight. You'll be hitting the bathroom more often, which is normal, as the pregnant uterus will be pressing on your bladder. Alas, many pregnant women do experience some constipation from normal pregnancy hormones, so drink lots of fluids and do incorporate more fiber into your diet on a regular basis.

Second Trimester

By the beginning of the second trimester, most women feel more energetic and their nausea begins to subside. The bad news: some women experience headaches. It's important to stay hydrated — acetaminophen usually helps. Lots of organ development is occurring in the fetus at this time and you can start seeing the external genitalia. If you have an ultrasound at this point, decide in advance whether or not you want to know the sex of the baby! On a physiology level, your circulating blood volume will rise 50% over your non-pregnant baseline, so you may become more aware of your heart beating, and you may become a bit more short of breath climbing up stairs (but do keep taking the stairs as long as you're healthy – it’s great exercise).

By the end of the second trimester, the major organ systems have developed their basic architecture, but the brain is constantly developing. You will most likely feel pretty good (no nausea or headaches); you'll just feel big. Do try to stay active, which will help minimize your "physically large feelings".

Third Trimester

Most women feel some tightening of their uterus during the last trimester called Braxton-Hicks contractions, which help the uterus practice for labor. If they start coming regularly or become painful, and you're several weeks away from delivery, call your obstetrician or midwife.

During your last trimester, your healthcare provider will ask you to come in for more frequent checkups to help avoid any end of pregnancy complications. They will take your blood pressure, look for any swelling and check for any protein in your urine. The great news is that most of the time, all will be well. There is very little that cannot be cured by delivery of the baby.

Post Pregnancy

Some women refer to the post-partum timeframe as the "fourth trimester". During this time, it's important to continue taking care of yourself – you'll most likely be thinking mostly about that baby. Do not hesitate to take kind offers from friends and family to help with the baby, so that you can take a nap. And don’t worry what your house looks like – your friends want to see the baby, they've seen your house before! You may need to wait about six weeks or so for the baby to smile at you, but once they do it will all be amazingly worthwhile!

Mary Jane Minkin, M.D.

Mary Jane Minkin, M.D., is a board-certified obstetrician/gynecologist in private practice in New Haven, Connecticut, and a Clinical Professor of Obstetrics and Gynecology at Yale University School of Medicine. She is a lead author or co-author of articles in numerous peer-reviewed journals, including Obstetrics and Gynecology and Journal of Reproductive Medicine, as well as coauthor of A Woman's guide to Sexual Health (Yale University Press, 2005).

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