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Pregnancy Timeline

May 26, 2020

Getting the news that you are pregnant can be thrilling, shocking or both.

The Pregnancy Timeline was developed as a week by week guide to pregnancy which takes in how the baby develops and changes to the mother’s body.

1 – 4 Fertilization occurs and a ball of quickly multiplying cells embeds itself in the lining of the uterus.
5 The mass of cells is developing fast and becomes an embryo.  For many women the first sign of pregnancy is a missed period.
6 The embryo officially becomes a fetus.  It is about the size of a baked bean and its spine and nervous system begin to form.
7 The baby’s heart is beginning to develop.  Morning sickness and other side effects of early pregnancy may occur.
8 It is quite common to have a first scan at this stage if the woman has had a previous miscarriage or bleeding.
9 The fetus is about 5 cm long with its head tucked onto its chest.  It has most of  its major organs and eyes and ears are developing.
10 A scan at 10-13 weeks is recommended to determine and confirm the date of the pregnancy.
11 The umbilical cord is fully formed providing nourishment and removing waste products.  The fetus looks fully human now.
12 By this week the threat of miscarriage is much reduced.  Many women announce their pregnancy to friends and colleagues.
13 The woman’s uterus is becoming larger and is starting to rise out of the pelvis.  The fetus can move its head quite easily.
14 Third of the way through.  The average pregnancy lasts 266 days or 280 days from the first day of last period.
15 Screening for Downs syndrome is offered about now.  A simple blood test is carried out first, then further tests may be offered.
16 The fetus now has toes and fingers, nails, eyebrows and eyelashes.  It is also covered with downy hair.
17 The fetus can hear noises from the outside world.  By this stage the mother is visibly pregnant and the uterus is rising.
18 By this stage the fetus is about 11 cm long and is moving around a lot probably enough to be felt.
19 By the end of this week the fetus is 20 cm long and weighs about 300g.  Milk teeth have formed in the gums.
20 Half way through pregnancy, now all mothers are offered a scan.  The fetus develops a waxy coating called vernix.
21 The mother may feel short of breath as her uterus pushes against her diaphragm leaving less space for the lungs.
22 Senses develop taste buds have started to form on the tongue and the fetus starts to feel touch.
23 The skeleton continues to develop and bones that form the skull begin to harden but not fully.
24 Antenatal checkup and scan to check the baby’s position.  A baby born this early does sometimes survive.
25 All organs are now in place and the rest of the pregnancy is for growth. Preeclampsia is a risk from here onwards.
26 The fetus skin is gradually becoming more opaque than transparent.
27 The fetus measures about 34cm and weighs about 800g.
28 Routine checkup to test for preeclampsia.  Women with Rhesus negative blood will also be tested for antibodies.
29 Some women develop restless leg syndrome in their third trimester.
30 Braxton Hicks contractions may begin around now.  They are practice contractions which don’t usually hurt.
31 The fetus can see now and can tell light from dark.
32 Another antenatal appointment.  The fetus is about 42 cm and weighs 2.2 kg.  A baby born now has a good chance of survival.
33 From now the baby should become settled in a head downwards position.
34 The mother may find it more difficult to eat full meals as the expanded uterus presses on her stomach.
35 If the mother has been told she may need a planned caesarean, now is a good time to discuss it further.
36 The baby’s head may engage in the pelvis any time now.
37 The baby’s lungs are practically mature now and it can survive unaided.  The final weeks in the womb are to put on weight.
38 Babies born from this week onward are not considered early.
39 Another antenatal appointment.  The mother has reached her full size and weight by now.
40 In theory the baby should be born this week.  The mother’s cervix prepares for the birth by softening.
41 First babies are often up to a week late but if there are signs of distress to mother or child the birth will be induced.