Aged gametes, adverse pregnancy outcomes and natural family planning. An epidemiologic review.

Unconfirmed epidemiologic studies suggest a possible increased risk of birth defects associated with Natural Family Planning (NFP) use, and an increased incidence of spontaneous abortion or frequency of chromosomal abnormalities in abortuses associated with conceptions outside the most "fertile period". The risk is approximately two- to four-fold, but the evidence is by no means conclusive. The implication for NFP depends on the frequency of method failures in user populations, but is not likely to constitute a major hazard. Further research could utilize a data bank of NFP charts.

PIP: Unconfirmed epidemiologic studies of adverse pregnancy outcomes associated with aging gametes have found a significant increased risk of spontaneous abortion and polyploid chromosomal abnormalities among abortuses and a nonsignificant risk of chromosomal defects at birth. These risks are generally between 2 and 4-fold. These findings raise concern about method failures associated with natural family planning (NFP). Contraceptions due to intercourse before the fertile period could arise from aged sperm, and conception after the fertile period could occur with a postovulatory aged ovum. However, risk estimates derived from unconfirmed studies must be interpreted with caution due to the problem of ascertaining whether a conception arose from aged gametes. Epidemiologic studies of birth defects are further complicated by the diverse etiology of the anomalies, the timing of observation, the confounding effects of factors such as maternal age or other potential teratogenic exposures, and the potential for bias in maternal recall. The implications of these findings for NFP depend on the frequency of method failure, which does not appear to be high. Resolution of the question of whether NFP is associated with an increased risk could be obtained through a review of NFP conception charts in which conceptions due to method or user failure were identified and the pregnancy outcomes were ascertained. The large sample size required for such a study could be attained by international collaboration among NFP organizations and establishment of a data bank of contraception cycles.

PMID: 6509983 [PubMed - indexed for MEDLINE]