Expecting a Baby? (One Born Every Minute)
Your baby continues to grow fast, from a small fetus at the start of the trimester to a fully formed baby at the end of Week 26. You will start to feel your baby move at around the middle of the trimester and, as the baby increases in size and strength, these movements will become more vigorous and defined.
The second trimester is the time in pregnancy when most women feel at their best. The unpleasant early symptoms, such as tiredness and morning sickness, have usually disappeared; you are starting to look pregnant, but your bump is not so large that it hinders you; and you feel optimistic that your pregnancy is now ‘safe’, because the placenta rather than just the maternal hormones is now fully supporting the pregnancy.
Reflex muscular activity is occurring, although you will not yet feel your baby moving. The external genitalia have differentiated into male or female, allowing the sex of the fetus to be determined by ultrasound scan. The fetus starts to produce its own blood cells, rather than using only those supplied by the placenta. The heart still beats at around 110–160 beats per minute (compared to an adult’s average of 70 bpm), but this slows down gradually as the pregnancy progresses. (A child’s heart rate only reaches that of an adult at about ten years of age.)
Downy, colourless hair, called lanugo, starts to develop and now breaks through the skin on the eyebrows and upper lip. The lower limbs are fully formed and growing fast, and
all limbs are more in proportion with the rest of the body. The arms are now long enough for the hands to meet in front of the chest. The central nervous system continues to develop during these early weeks of the second trimester, allowing
supporting your pregnancy
By the start of the second trimester, the structure of the placenta is developed and it is fully functioning, ensuring that the pregnancy continues to thrive. It provides all the oxygen and nutrients, via the umbilical cord, that the fetus requires for continued growth. The placenta also acts as a barrier against many (though not all) infections, as well as reducing the harmful effects of medication, drugs, alcohol and tobacco – although it cannot eliminate them entirely.
The placenta has now taken over the production of the four main hormones: oestrogen, progesterone, human placental lactogen and BhCG. While production of BhCG peaked at Weeks 10–12 and then declined sharply (see p.91), the levels of the other three continue to rise throughout this trimester. These hormones are essential for fetal growth and for enabling your body to adapt during pregnancy and to prepare for it birth and breastfeeding.
or an increasingly wide range of movements. These include reflex facial movements, which can be seen on an ultrasound scan, so that it looks as if the fetus is frowning or grinning. Indeed, the face looks more human now, because the eyes are positioned at the front. Although the eyelids are still closed, the retina at the back of the eyes is sensitive to light. The fetus measures 80 mm crown to rump and weighs 45 g.
Many women experience a heightened sex drive in pregnancy, and especially in the second trimester when they are feeling at their best. This is possibly due to increased levels of hormones flooding through your body and the greater blood flow to the pelvic region. As your pregnancy progresses, your changing shape will mean that you may need to find alternative positions for sex. See Box on p.96 for more information about sex in pregnancy.