A woman holding a packet of birth control pills.
In a study published last month, Dutch researchers suggest that the use of birth control pills close to the time of conception may increase certain pregnancy risks.
Specifically, the use of oral contraceptives is associated with a modest increase in risk of preeclampsia, premature birth, and low birth weight. However, it’s suggested that the risks differ depending on the timing of discontinuation, and the amount of estrogen and progestin content in the birth control pill.
There’s a lack of systematic and comprehensive data on the peri-conceptional use of oral contraceptives and pregnancy complications and birth outcomes. Dutch researchers have partially filled that void. In a large prospective study, researchers in the Netherlands, at the Radboud University Medical Center in Nijmegen, examined data from nearly 7,000 pregnant women. About 1050 of them, or 15%, became pregnant within three months of stopping the pill. This group was compared with pregnant women who had not used the pill for a longer period of time. What the researchers observed was that in the first group preeclampsia and preterm birth (as well as low birth weight) occurred more than one and a half times as often as in the second group. High blood pressure and protein in the urine are key features of preeclampsia, while preterm birth indicates a birth that occurs before the 37th week of pregnancy.
The researchers emphasize that in absolute terms the complications were relatively rare, even in women who became pregnant shortly after stopping the pill. Specifically, about three percent of women experienced preeclampsia and six percent premature birth.
Nonetheless, the researchers recommend that women who have just stopped taking the pill to wait three months before becoming pregnant.
The study also shows that different variants of the pill are associated with complications. In particular, preeclampsia was more common when using the pill from the first and second generations, while preterm births were more common in the third generation. There wasn’t enough data to derive reliable conclusions from the fourth-generation pill.
Combined oral contraceptives contain two hormones, an estrogen, such as ethinylestradiol, and a progestin. Progesterone is the naturally occurring hormone in the body, while progestin is a synthetic hormone that mimics progesterone. The first generation progestin includes norethindrone and norethisterone; the second generation, levonorgestrel and norgestrel; the third generation, desogestrel, gestodene, and norgestodene; and the fourth generation progestin, drospirenone and dienogest.
Lead researcher Marleen van Gelder explains: “Different generations contain a different type of progestin. This may play a role in the development of the complications.” To illustrate, high estrogen doses were associated with enhanced pre-eclampsia risk, whereas low to moderate estrogen doses were associated with increased risk of adverse birth outcomes.
The newer generation combination pills are associated with far fewer side effects – nausea, bloating, weight gain – than the first generation oral contraceptive. Moreover, the pill has been used to prevent pregnancy relatively safely and effectively for many decades. Further, its usage doesn’t affect the ability to get pregnant. In other words, the body doesn’t need to time to “clear” birth control hormones. Once a woman stops taking the pill, the hormones will be out of the system in a matter of days and she can start ovulating and conceive almost immediately.
However, the new Dutch study does indicate a possible correlation between the use of birth control pills at or near the time of conception and certain pregnancy complications.
Previous studies looked separately at preeclampsia or preterm birth risks. For instance, a study from more than 40 years ago suggested that women who discontinued oral contraceptives as recently as two months before conception did not differ significantly with respect to incidence of preeclampsia at delivery than women last exposed three to 12 months before. And, a Norwegian study from 2015 showed a positive association between use of a combination oral contraceptive and preterm birth and low birth weight.
The Dutch study appears to confirm the Norwegian finding, in addition to suggesting a modestly enhanced risk of preeclampsia. In brief, the Dutch research demonstrated that any peri-conceptional use of oral contraceptives was associated with increased risks of pre-eclampsia, pre-term birth and low birth weight. Additionally, such associations were strongest when the pill was discontinued between zero and three months before conception.