Many expecting couples wait until the end of the first trimester — around week 13 — to tell friends and family about their pregnancy. And there are quite a few reasons behind it.

First, the risk of miscarriage. The first trimester is a tremendous time of development and change for the parents as well as their little one. With all that change comes some risk that the pregnancy might not carry to term.

Unfortunately, between 10 and 25 percent of known pregnancies end in miscarriage, and roughly 80 percent of them occur in the first trimester.

Most miscarriages are caused by factors beyond a mother's control. (In fact, that's why a lot of members of the medical community are against using this term.) About half are caused by chromosomal abnormalities, which means that the baby doesn't develop properly.

Other causes of first trimester miscarriage include:

• illness in mother;
• luteal phase defect (problem with a woman’s monthly cycle);
• hormone imbalances;
• adhesions (scar-like tissue) in uterus.

Age is another factor that contributes to the risks. Here are the chances of a miscarriage at different periods of a woman's life:

• Women ages 35 and under: 15 percent;
• Women ages 35 to 45: 20 to 35 percent;
• Women ages 45 and older: 50 percent.

If a developing baby lives to 7 weeks with a heartbeat, the risk of miscarriage drops to just 10 percent. In those beginning weeks when the risk is highest, women may not even know they're pregnant unless they've taken an early test.

After week 12, the risk of miscarriage falls to 5 percent for the rest of the pregnancy.

Given these numbers, it's understandable why so many parents wait until the risk of miscarriage drops before they announce about their pregnancy to the rest of the world. Having to tell people the sad news of a miscarriage shortly after announcing their pregnancy can be really difficult.

Another reason couples wait until the end of the first trimester has to do with prenatal checkups. Their first appointment may be around week 8 of pregnancy, or even later.

During the first visit, their provider will run tests to confirm the pregnancy, estimate the due date, screen for infections, and determine the general health of the mother and the baby.

For some couples, hearing that heartbeat for the first time or having an ultrasound to date the pregnancy is reassuring before announcing it to everyone.

If conceiving was problematic, the mother had a previous pregnancy loss, or had a stillbirth, couples may want to wait even longer than 12 weeks to share news of their pregnancy. And there's nothing wrong with it. (Something I can't say about most of the pictures in this list.) The decision is entirely up to them.

In these cases, they might share the news with some additional information:

• having an ultrasound that shows the baby is healthy;
• finding out the sex of the baby;
• reaching the halfway mark of pregnancy (week 20);
• reaching a personal milestone (e.g., when it starts showing).

Sometimes telling just one close friend or family member can be helpful. Especially if you're feeling anxious. But you may also want to tell your employer about your pregnancy right away if your job requires you to do something physical that might be dangerous. These hazards might include:

• bending repeatedly at your waist (more than 20 times per day);
• standing for long periods of time;
• lifting heavy things, like boxes, more than once every five minutes;
• being exposed to chemicals.

Nearly 3.7 million babies were born in the US in 2021; that's about 46,000 more than were born in 2020, but the 1% increase still put the number short of 2019 levels.

According to Beth Jarosz, a demographer and program director with the nonprofit Population Reference Bureau with a focus on child well-being, the drop in birth rates in 2020 was one of the largest in decades, and the slight rise in 2021 "doesn't necessarily mean that that declining trend is over." So whether we'll see more or less pregnancy announcements online is still unclear. Let's just hope that the ones that do cross our radars will be better than these!