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Growth and development in pregnancy

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Congratulations on your pregnancy.

It’s important to find a Lead maternity carer midwife (LMC) as soon as possible. Choosing a midwife has been made easier with the Find Your Midwife website.

The Find Your Midwife website helps you to find the right midwife for you. Women who are having a second or subsequent baby may already have decided to contact the midwife who cared for them before, but if this is not you then the Find Your Midwife site has regional information and information about each midwife including their availability.

Your baby will change a lot throughout a typical pregnancy. This time is divided into three stages, called trimesters. Each trimester is a set of about three months. Your midwife will probably talk to you about your baby’s development in terms of weeks. So, if you are three months pregnancy, you are about 12 weeks.

It may be easier to think about the baby’s growth and development in pregnancy by dividing pregnancy into three trimesters.

  • 1st trimester – Conception to 12-14 weeks
  • 2nd trimester – 14 weeks to 28 weeks
  • 3rd trimester – 28 weeks to 42 weeks

1st trimester – Conception to 12-14 weeks

Signs of pregnancy will be noticed by most women during this first trimester as there are many hormonal changes occurring. Symptoms can include tiredness, morning sickness, breast tenderness and the need to pass urine more often than usual. Missing a period can be the first sign of pregnancy, and if a pregnancy test is carried out after the period was due the results are likely to be accurate. Sometimes in early pregnancy a small amount of spotting or bleeding is experienced, this is usually normal and caused by the fertilised egg attaching to the lining of the uterus. If concerned, you can talk to your LMC midwife or gp.

This first three months of pregnancy start with the first day of the last menstrual period and include conception. Conception generally happens around fourteen days after the first day of the last period. In this time period the baby develops from a collection of cells, and implants as an embryo on the wall of the uterus. The embryo grows rapidly and receives oxygen, blood supply and nutrition from the developing afterbirth (placenta/whenua) and all this development takes place inside a watertight sac called the amniotic sac. The placenta is an essential organ that provides oxygen and nutrients to your developing baby. It also plays a significant role in the health of your pregnancy. The developing baby is attached to the placenta/whenua by the umbilical cord. In these early stages of pregnancy, although the baby is developing rapidly and is fully formed with all organs already developed by twelve weeks, it is still very small, so a baby bump may not be noticeable to most people until well after twelve weeks of pregnancy. Although changes are not so obvious on the outside, babies are busy developing inside. Babies make sucking movements and swallow the amniotic fluid (waters) that they are floating in, and also move about freely in the amniotic sac, but these movements are not usually felt by the mother just yet. The fingernails and toenails are also starting to develop.

It is not always possible to hear the baby’s heartbeat during this first trimester but midwives may try and listen to the baby’s heartbeat between the tenth and twelfth week of pregnancy using a handheld Doppler (ultrasound) device. This amplifies the baby’s heartbeat so it can be heard by parents. It can be difficult to hear the heartbeat at this stage because of the baby’s position, the baby moving around a lot and the mother’s uterus (womb) still being low in the pelvis.

During this trimester midwives plan midwifery care with the pregnant woman. This includes pregnancy, birth and postnatal care, and a full health assessment will also be carried out. Frequency of visits with the midwife during pregnancy and birth place options are discussed. The midwife can also provide information about the range of pregnancy and parenting education options available. The growth and development of the baby is usually a topic of discussion at these sessions.


Assessments, tests and screening

Keeping well  during pregnancy

2nd trimester – 14 weeks to 28 weeks

By this stage the majority of women will have stopped experiencing early pregnancy discomforts such as morning sickness and tiredness although it is not unusual for them to return occasionally. The baby bump is now noticeable and from about 20 – 22 weeks of pregnancy small flutters might be felt as the baby moves around in the amniotic sac. For some women who have had a baby before they might become aware of the baby’s movements as early as 16 weeks or so because they recognise the familiarity of them. Towards the end of this trimester the mother may also notice the baby gets hiccoughs quite regularly and she will feel these jerky movements.

Although all the organs were already formed by 12-14 weeks the baby continues to grow rapidly and the eyes (which will be opening by the end of this trimester), eyelashes and eyebrows are now forming along with the genitals. Babies can suck their thumbs, yawn and stretch and are covered in soft downy hair which is called lanugo. Babies are also covered in a creamy waxy whitish coating called vernix. This protects the developing skin underneath.

The midwife will be able to hear the baby’s heartbeat now through a hand held Pinard which looks like a small trumpet. One end goes on to the pregnancy bump and the other end to the midwife’s ear. A fetoscope may be used that looks a bit like the usual stethoscope. Midwives may also use a handheld Doppler (ultrasound) device which amplifies the baby’s heartbeat so it can be heard by parents as well.

The baby’s heart rate is usually between 110 beats and 160 beats per minute so it can sound very fast to parents, but this heart rate is normal.

Although those early pregnancy discomforts have all hopefully disappeared by now some women may continue to experience heartburn or nausea into the second trimester. Appetite may increase and weight gain is noticeable. Gaining weight during pregnancy is normal because of baby growth, the growth of the placenta/whenua and the amniotic fluid around the baby. There is no exact recommended healthy weight gain in pregnancy that applies to all women as some women may need to gain more weight and some women less. It’s a good idea to talk to the lead maternity carer midwife about foods to avoid and weight gain, and this is particularly important if there are any concerns or anxieties about weight gain and a healthy diet.


Assessments, tests and screening

Keeping well  during pregnancy

3rd trimester – 28 weeks to 42 weeks

The baby’s hearing is fully developed now and they will be able to hear the sound of their parent’s voices as well as other sounds from outside. The brain is developing rapidly and most of the baby’s internal systems are functioning. Lungs are not yet mature but the baby is practicing and making breathing movements now. Most of the lanugo (soft downy hair) is shed from around the 32nd pregnancy week and the remainder will be shed by the baby during the first week after birth. The vernix on the baby’s skin starts to increase around the 36th week of pregnancy. Some babies are born with very obvious vernix on their skin and it is recommended that this is left on the skin as a continued protection. It is absorbed within the first few days.

The baby is rapidly growing and gaining weight in this trimester and this means that fat stores are being built up ready for the birth. The development of sleep-wake patterns is also noticeable in this trimester and mothers get to know their baby’s patterns. In the third trimester as pregnancy advances it is normal to perceive increasingly strong movement, episodes of movements that are more vigorous than usual, fetal hiccups, and a daily pattern that may involve strong movements in the evening. Your knowledge of your baby’s movement patterns including busy and quiet times is important. There is increasing evidence emerging about what to expect of baby’s movements, changes in your baby’s movement patterns and expectations of when the quiet times ‘should’ be. If your baby usually gets busy at night, don’t be worried by this. If you’re concerned that your baby is moving less often, less strongly or not moving in the evening as they normally would, don’t wait until the next day for a check-up.

Because the baby is gaining weight and this is putting pressure on the mother’s internal organs, mothers may start to experience more heartburn, as well as backache and the need to pass urine more frequently. As the baby grows and crowds the abdominal cavity, you may have a hard time taking deep breaths or getting comfortable at night for sleep. The space for the growing baby to move around is also reducing and the baby will start to move into a position to prepare for labour and birth. If this is the first baby the baby will begin to move lower down into the mother’s pelvis from around 36 weeks and in most cases this is the head that moves down into the pelvis by 38-39 weeks. If it is not a first baby then the baby may stay out of or just at the brim of the pelvis until very close to labour.

By 36 weeks or so the baby’s lungs are more mature and getting the baby ready to be able to breathe easily once it is born. The last few weeks of the pregnancy support the baby to complete the growth and development needed to be ready for life outside the womb.

Visits with the midwife are more frequent during this trimester and the midwife will assess the growth of the baby in relation to its age and also the position the baby is in.