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13 Weeks Pregnant: Your Baby’s Development

Now that your little one has developed all of the critical body structures, the organs are hard at work. The liver secretes bile, the pancreas produces insulin, and the kidneys form urine to carry waste away (into the amniotic fluid). Your little one’s intestines, which have partially resided in the umbilical cord, have moved back into the abdomen now that there’s enough room to accommodate them.

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What else is happening with your baby? Even though tiny coos and cries may be months in the future, little vocal cords are already starting to develop in preparation for communication with you after birth.

13 weeks pregnant is how many months? You’re correct if you’ve guessed “three!” This is the stage where your blood supply is fully linked to your baby’s placenta, which will continue to grow as your pregnancy progresses.

By the time you give birth, the placenta will weigh between one and two pounds all by itself.

If you’re 13 weeks pregnant with twins, then you can read more about your babies’ development in our weekly twin pregnancy overview.

How Big Is Your Baby at Thirteen Weeks?

Your fetus is about the size of a large plum or a small peach. The average fetus weighs just a little under one ounce, and measures between 2.6 to 4 inches long. The head is now approximately one-third the size of the body. When your baby is born, the head will be only a quarter of his or her length.

pregnancy week 13 fetus

Mom’s Body at 13 Weeks Pregnant

You’ve just about made it to your second trimester, which many women describe as the honeymoon period of pregnancy. The discomforts of the first trimester– fatigue, nausea [https://www.pampers.com/en-us/pregnancy/pregnancy-symptoms/article/morning-sickness-symptoms-remedies], and frequent urination – often ease up a bit and you finally start to enjoy being pregnant. Many women even feel a surge of energy during this trimester.

If you’re still feeling fatigued and nauseous, you’re not alone. These symptoms sometimes stick around through the fourth and fifth months of pregnancy. Breast tenderness will probably continue on and off, and other issues like constipation, bloating, and heartburn are normal too.

13 Weeks Pregnant: Your Symptoms

  • More Vaginal Discharge – A mild-smelling (or even odorless), clear to milky-colored discharge known as leukorrhea may increase at some point during your pregnancy. It’s caused by increased blood circulation and your old friends, hormones. You might be surprised to learn that this discharge has a unique purpose: it keeps your birth canal clear of harmful bacteria. Unfortunately, leukorrhea can get messy; panty liners can be a big help.

  • Changing Sex Drive – It's perfectly normal for a woman and her partner to feel an increase or a decrease in sexual desire at various times during pregnancy. Go with the flow! If both of you feel the urge, go ahead and enjoy intimacy. Don't worry about your bump – your baby will be safe! Talk to your healthcare provider if you’re worried or have questions about this or anything else. Note that you might have to abstain from sex if you have complications including a history of miscarriage or are at risk of early labor.

  • Hormones Contribute to Heartburn – Heartburn and indigestion can come and go throughout your pregnancy as your baby moves from one position to the next, and as pressure on your digestive system changes. Part of the issue is that the hormone relaxin causes the muscle located at the top of your stomach to relaxes during pregnancy; this allows stomach acid to travel up into the esophagus, particularly when you’re lying down or if you’ve eaten a large meal. You can reduce the pain by avoiding triggers such as chocolate, peppermint, caffeine, citrus, and fatty or spicy foods.

  • Constipation – Hormones strike again! Progesterone and estrogen play an important role in pregnancy, but right now they might be wreaking havoc on your insides, causing your GI tract to move waste slower than usual. This means that you may start to feel a bit backed up – and you might even feel abdominal pain as a result. Adding more fruits, vegetables, and whole-grain foods to your diet increases your fiber intake and helps keep things moving; drinking prune juice can help, and so can adequate hydration and regular exercise.

  • Colostrum Production Begins – You may start to notice the production of colostrum anytime now. Colostrum is the milk that appears for the first few days after your baby's birth; it sometimes shows up as a thin, sticky breast discharge during pregnancy, and is completely normal. Disposable or cotton breast pads (without plastic liners) can help absorb the leaking fluid.

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13 Weeks Pregnant: Things to Consider

  • Have you shared the good news with your family and friends? The beginning of your second trimester is a great time to do this if you haven’t already. Of course, the decision about when to start spreading the word is totally up to you!

  • It's wise to make a plan to let your boss know that you’re expecting, if you haven’t already. You’ll want to keep your employer and colleagues in the loop so they can make plans for accommodating your absence during your maternity leave.

  • Working out? If yes, keep it up! If no, consider talking to your healthcare provider about starting a basic fitness routine that includes things like walking, swimming, and maybe yoga, as long as your doctor gives you the go-ahead. Your muscles will thank you later – both during the last six months of your pregnancy, and during your new baby’s first few months, when increased fitness will help you deal with all the extra stress that’s placed on your body. If you are doing abdominal exercises that have you lying flat on your back, you may want to look for alternatives during pregnancy, since the weight from your uterus can cause less blood to return to your heart. This can reduce the amount of blood that returns to your heart, and it can cause your blood pressure to dip.

13 Weeks Pregnant: Ask Your Doctor

  • Should you have an ultrasound anytime soon? Whether you get a yes or a no, try to schedule your appointment for a time when dad can join you.

  • Cramping sensations are often caused by round ligament pains from your growing uterus. Talk about what’s normal and what isn’t, and if you ever have cramping accompanied by bleeding, get to the doctor right away.

  • Am I gaining the right amount of weight? Now that your first trimester is nearly over, it’s time to check your weight. It’s normal for the average woman to have gained between 1 1/2 and 4 1/2 pounds by this point; for example, if your weight was 140 pounds when you became pregnant, the scale should show something between 141 and 146 pounds now.

  • Call your doctor right away if you experience pain combined with bleeding, chills, or fever.

13 Weeks Pregnant: Your Checklist

Look for some comfortable, stylish clothes to accommodate your baby bump

Enjoy the beginning of your second trimester, when you may have more energy and less nausea

Think about sharing your big news with your wider circle of family and friends

Sign up for even more weekly pregnancy tips.

13 Weeks Pregnant: Your Checklist

Look for some comfortable, stylish clothes to accommodate your baby bump

Enjoy the beginning of your second trimester, when you may have more energy and less nausea

Think about sharing your big news with your wider circle of family and friends

Sign up to get weekly pregnancy tips