The second phase of the glorious 9-month journey, the second trimester comes with a new set of body changes for you while your baby continues developing in the womb. He is almost as big as a lemon at the start of this trimester , growing about the size of a zucchini by the time you enter the next stage . Another good news is that the risk of miscarriage has now dropped considerably, as over 80% pregnancy loss occurs within the first 13 weeks .
When does the second trimester begin
Second trimester weeks
|Month of Pregnancy||Week by Week|
|Fourth month||14, 15, 16, 17|
|Fifth month||18, 19, 20, 21|
|Sixth month||22, 23, 24, 25, 26|
Baby development during the second trimester
These thirteen weeks see major developments in the growing fetus as the skeleton and other bony structures begin to mature, followed by the fat layer under his translucent skin . Other milestones include your baby learning to swallow and suck on his tiny thumbs .
By the end of the trimester, his hearing skills  are developed enough for him to respond to your voice. Some women are lucky enough to even feel their baby’s first movements (quickening) during this period [8, 9].
Second trimester symptoms and body changes
These 13 weeks are often considered the best in the 40-week journey as most of the unpleasant symptoms from the first trimester begin to subside around this time, while it is still too early for the late pregnancy symptoms to come. The hCG hormone levels gradually decrease, with the better balance of estrogen and progesterone levels contributing to reduced symptoms of fatigue and morning sickness . However, constipation, heartburn, indigestion and frequent urination are some of the symptoms that are likely to remain .
You will probably start to feel some of the pregnancy aches as the growing uterus leads to back pain and round ligament pain . Many women, especially those in their second or subsequent pregnancy, start getting Braxton Hicks contractions or the false contractions usually after the 20th week .
Weight gain during the second trimester
Since the nausea and vomiting takes a back seat around this time, your appetite is likely to get better while you may be having certain food cravings as well . However, it is crucial to keep in mind that eating for two does not mean having two portions of every food on the table (although you could easily eat that much if given a chance). You need no more than 300-500 extra calories per day, as the ideal weekly weight gain level during these three months is around 1/2 to 1 pound .
Second trimester: tests and ultrasound
An ultrasound scan is performed halfway through the pregnancy, between the 18th and 20th weeks (the anomaly scan), to evaluate the size and physical features of your baby . Your sonographer measures the baby’s head circumference to ensure proper skull and brain development .
The fetal skeleton is visible through the transparent skin  during early second trimester while an ultrasound also allows you to find out your baby’s sex after week 18 .
Second trimester screening
Maternal serum alpha-fetoprotein and multiple marker screening are both optional screening blood tests offered routinely during the second trimester. Depending on the medical history of the mother, one of these tests is performed to assess the risk of certain genetic disorders and neural tube defects such as Down syndrome, trisomy 18 and spina bifida [18, 19].
Things to keep in mind
- Warning signs: While occasional mild headaches are quite normal, make sure to contact your health care provider in case of sudden shooting headaches as they may indicate high blood pressure or even preeclampsia . Other possible warning signs at this stage include severe back or stomach cramps, bleeding, watery discharge or leaking amniotic fluid and diarrhea lasting for days .
- Fetal nutrition: The umbilical cord continues growing thicker to carry more nutrients to the developing fetus. But at the same time, harmful substances are also more likely to reach the baby through the cord. So, make sure to avoid tobacco, alcohol and other similar substances .
- Exercise: Working out throughout pregnancy is the best way to keep your weight gain in check, with swimming being a suitable exercise as the water helps you relax by supporting your growing belly. It is also about time you considered joining a prenatal yoga class .
Once you have taken care of your diet and lifestyle to keep your baby healthy, you can move on to the fun part. Short-listing the names you like for your coming baby, taking a babymoon, shopping for maternity clothes and decorating the nursery are just a few of the things you can do. But, don’t forget to be on a lookout for any abnormal signs.[ref]
- http://www.aafp.org/afp/2007/1101/p1341.html [/ref]