Ask an Expert: Getting pregnant after…

Editor's note: We receive a lot of questions regarding safe timing for attempting to conceive after various medical interventions. Here is our expert's response to many recent questions.

Q: How long should I wait to get pregnant after…
  • Having a medical procedure involving anesthesia?
  • Taking prescription medications?
  • Getting travel immunizations?
  • Undergoing chemotherapy?
  • Having uterine fibroids removed?
Answers from Angela Keating, M.D., board-certified obstetrician/gynecologist with Providence Medical Group Columbia Women's Clinic: 

This kind of pre-pregnancy health planning is very wise. The early weeks of pregnancy have a profound effect on the health of the embryo, and it's great to give the baby as healthy a start as possible.

If you have concerns about a potential pregnancy, make an appointment for a preconception counseling discussion. That's a good time to check your overall health, review your family history and address specific concerns.

Pregnancy after medical procedures
Anesthesia does not present a danger to pregnancy. After all, many women receive anesthesia during labor and delivery. If you have a surgery that involves the abdominal area, ask the surgeon about healing time. When your surgeon says you are fully healed, it is then fine to get pregnant.

Pregnancy after taking medications
The short answer: Wait at least one month after taking medications that could harm the embryo.

The better approach: Make an appointment with your OB/gyn, nurse-midwife or nurse practitioner three months before you'd like to try conceiving. Bring a list of your over-the-counter and prescription medicines. Discuss each one with your provider. You may need to avoid some medications completely. Your doctor may want you to taper off a drug. Or, for an ongoing condition, you may be advised to switch temporarily to a different medication that is safer in pregnancy.

Drugs differ in their potential effects on the growing fetus, and the level of knowledge available on each drug varies, as well. The Food and Drug Administration has categorized drugs with one of five letter grades to rate their known safety during pregnancy:
  • An "A" designation means controlled human studies have demonstrated no risks to the fetus. Examples are prenatal vitamins (in recommended doses) and Synthroid, a thyroid medication.
  • "B" means the medication is presumed safe, based on animal studies. No well-controlled human studies are vailable. Examples are Tylenol and many asthma and allergy medicines.
  • "C" means that safety is uncertain. Data from human studies do not exist. Animal studies have shown some question of risk to the fetus. Pregnant women may take these medicines if they clearly need them. Most drugs, whether prescription or over-the-counter, are rated C.
  • "D" means we have evidence of the medication possibly causing birth defects or other problems, but a pregnant woman might still need to take it because of her own medical needs. In this category, the benefits are seen as outweighing the risks. An example is anti-seizure medicine.
  • "X" means that proven risks to the fetus outweigh any possible benefits to the mother. Examples are thalidomide (approved as a treatment for leprosy) and Accutane, an acne medicine.
There are exceptions to the one-month off rule, such as some medications delivered in shot form. Allergy shots are fine throughout  pregnancy. But Depo-Provera, a long-acting form of birth control, can linger in a woman's system for six to nine months, diminishing her ability to conceive. Depo-Provera does not pose a risk to the fetus, but if you are planning a pregnancy, switch to a more temporary form of birth control nine months beforehand. When taking regular birth control pills, you can start trying to conceive as soon as you finish your pack of pills.

Pregnancy after travel vaccinations
Travel vaccines often come in two versions: “activated” vaccines, meaning those that use a weakened, live form of a virus, bacterium or toxin, and “inactivated” vaccines. The Centers for Disease Control and Prevention recommends that, before trying to conceive, women generally wait at least a month after vaccination with an activated dose. No waiting period is necessary if you have an inactivated vaccine.

Ideally, we'd like you to avoid malaria zones if you intend to get pregnant. But if you must go, finish a full course of malaria pills and wait a month before trying to conceive. See CDC recommendations on specific vaccines.

Pregnancy after chemotherapy
Chemotherapy kills all fast-growing cells, good and bad. It also injures the ovaries; depending on your age, your ovaries may or may not recover from the assault. (The younger you are, the better your chance of regaining ovarian function.) Our recommendation to patients with cancer is to wait to consider pregnancy until after you've had at least three menstrual cycles, three months in a row, that are normal.

After chemo, regular periods won't return until your body is fairly back to normal functioning anyway. This is a subject to discuss with your oncologist, not just your obstetrician or midwife. Your oncologist can help you anticipate and prepare for the potential effects that your specific chemotherapy regimen may have (the effects differ depending on the type of chemotherapy and the type of cancer).

Your oncologist also may want you to wait a certain period of time before trying to conceive to make sure the cancer does not spread or recur. (If cancer does recur after a woman becomes pregnant, patients usually can undergo chemo during the second or third trimester.)

Pregnancy after fibroid surgery
The impact of fibroid surgery depends on how many fibroids you have, their size and where they are growing in the uterus. If the fibroids have enlarged the uterus only mildly, we generally would not recommend fibroid surgery before pregnancy – but it depends on the location of the fibroids.

If you do need fibroid surgery, we'd typically ask you to wait six to 12 months afterward before attempting to conceive. This gives the uterus time to heal to the fullest extent possible. That timeframe is based on studies related to uterine healing after Caesarian section and discussions with infertility experts.

Few studies have looked at fibroid surgeries and subsequent pregnancy. Besides that, it's hard to pool the data because women's cases vary so much. We strongly suggest you speak with your surgeon, before and after fibroid surgery, about your wish to become pregnant. 

Before surgery, ask for a full explanation of the risks related to pregnancy. After surgery, ask what the surgeon found and did (this can differ from what is expected). Ask about the timing of a potential pregnancy and any precautions you should take related to pregnancy or labor. Very importantly, ask the surgeon to make a note in your record as to whether you can or cannot go through labor.

Here's why: Uterine fibroids can grow singly or in clusters. They can range from as small as an orange seed to bigger than a grapefruit. They are nearly always non-cancerous. And they appear in three basic areas: the outer surface of the uterus; the inner surface of the uterus; within the uterine muscle – or any combination.

Fibroids that penetrate the layers of uterine muscle pose the greatest concern in terms of a future pregnancy, because removing them involves the biggest impact on the uterus.  The problem is not the fibroids, per se, but how much their removal might damage healthy uterine tissue.

Depending on the incision and the extent of the fibroids, a patient can be at higher risk of uterine rupture. Muscle that has been cut cannot heal to 100 percent of its pre-surgical strength. Uterine rupture can involve dangerous bleeding, no matter how much time has elapsed before pregnancy. Thus, we sometimes recommend that specific patients deliver only by Caesarian section to avoid having contractions that would stress the scarred uterine muscles during labor. 

On the other hand, “pedunculated” fibroids – tumors that hang loose on a stalk, either on the inner or outer surface of the uterus – may not disturb your plans for motherhood one bit. If your surgeon just needs to shave off a couple of these fibroids, you are at no increased risk for a complicated pregnancy or delivery.

September 2005

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