20 Weeks Pregnant - halfway there? A discussion on due dates

Weekly pregnancy updates from a childbirth educator, doula and mum to 2 little girls. Come and join me on my journey as I share how I’m feeling, how baby is developing, what I’m doing to prepare, and some favourite resources!

A common comment to hear at 20 weeks pregnant is, “Oh, so you're halfway there!” This is probably roughly true, but let’s talk about due dates! Firstly, have you ever wondered who decided that a pregnancy lasts 40 weeks, and how they came to that conclusion? And most of all, how on earth is it that 40 weeks has come to be seen as a deadline, as if the mother or baby are all of a sudden at high risk from one day to the next?

The truth is, lengths of gestation vary from mother to mother, and also significantly from ethnic background to ethnic background. For example, studies have shown that black mothers tend to go into spontaneous labour on average 5 days earlier than white mothers. We can’t pick a number out of the air and apply it to everyone! Different babies mature at different rates, and individuality should be respected.

Full-term Pregnancy according to the WHO

The World Health Organisation maintains that a “full-term pregnancy” is one that runs to between 37-42 weeks. This means that using terminology such as “overdue” before 42 weeks is quite out of line with global standards. So why are so many women pressured into an induction before 42 weeks just because of the number of weeks’ gestation? The reason given tends to be that after 41 weeks there is an increased risk of stillbirth — in fact, the rate of stillbirth doubles. This sounds so scary, right?! But before panicking, ask your provider what the absolute risk of stillbirth is? Studies show the risk increases from 1 in 1000 at 41 weeks, to 2 in 1000 at 42 weeks. No mother wants their baby to be one of those, but many mothers would prefer to monitor their baby’s wellbeing and wait for the baby to decide when he or she is ready to be born! Make sure you have all the facts, and then YOU make the decision which you feel is best for you and your baby!

Calculating the length of gestation

And back to the length of gestation... whose calculations are you going by anyway? If you know when you conceived, it seems reasonable to work with the dates that you know to be accurate -- remembering that the length of time it takes to reach maturity varies between babies. But if the doctors are basing your "due date" off your last menstrual period or off a scan, there is a lot of room for error! Ultrasounds calculate dates based on averages, while some adults (and their babies) are naturally bigger or smaller than average. Menstrual periods can be quite irregular, and unless you know for sure when you ovulated/conceived they should generally be taken with a grain of salt!

For the record, I went into spontaneous labour with my babies at 39+5 and 41 weeks respectively, but I know full well that longer or shorter pregnancies can be perfectly normal. My mother typically went to 42+ weeks and had spontaneous labours with healthy babies. I have heard many reports of women giving birth after 43 weeks, because they have respected their baby's need to spend more time in the womb. And again, who is to say their 43 weeks wasn't actually 40-42 weeks if based on faulty dating? On the other hand, I know women whose “normal” is spontaneous labour before 39 weeks. We are all individuals, all different, and pregnancy care should take this into account!

Reasons NOT to wait for spontaneous labour

I do just want to emphasise that there are absolutely good medical reasons NOT to wait for spontaneous labour, such as if the mother has pre-eclampsia, placenta praevia or if it’s clear that the baby has stopped growing (IUGR), to name a couple. But simply a calendar date isn't an evidence-based reason to induce! Check down below in the resource section for links to articles on the evidence behind planning inductions. As always, parents should be given evidence-based information around whatever their situation is, so that THEY can make the right decision for their family.

What symptoms am I feeling?

Back in week 14 we talked about changes to the skin in pregnancy, such as the linea nigra or skin tags. I can now confirm I have my usual pregnancy skin tags popping up! Once again, I am getting them around my eyes and on my neck. Another common skin change in pregnancy is stretch marks. Not everyone gets them, though some have a lot, and others anywhere in between. Although it’s important to stay hydrated so the skin stretches more effectively, it seems that whether or not you get stretch marks is mostly related to your skin type, and isn’t something you can control. I know not everyone will agree with me, but personally I see stretch marks as a badge of honour, reminding me of the amazing things my body is doing or has done in stretching and growing to accommodate and nurture a growing baby... and then a second, and a third!

How has baby been developing this week?

Baby is now somewhere around 26cm long and weighing around 330g. An exciting development this week is that their inner ear and nerve endings are sufficiently developed to be able to hear sounds, such as your heartbeat and breathing. It will probably be another few weeks till they can hear sounds outside the womb — for instance, your voice or the music you play.

Your belly is growing and the stretching skin may become itchy. Drink plenty of water to stay hydrated and use hydrating creams to massage your belly if that helps. The top of the uterus is now as high as your belly button!

What am I doing to prepare?

After six weeks mostly away from home, between our Italy trip and travel back here in Australia for family weddings, this week is about adjustment, resetting, and getting back to normal. “Normal” will include time for regular exercise with a focus on birth preparation, as well as time spent on mental preparation for birth.

A favourite resource:

Dr Sara Wickham “Are there good reasons to induce labour?”; “Post-term pregnancy and induction of labour resources”.

Dr Wickham also has two books on this topic: “In Your Own Time: how western medicine controls the start of labour and why this needs to stop” and “Inducing Labour: making informed decisions”.

And that’s it for this week! 🌿💛

[Image credit: photo by Jill Sauve on Unsplash]