REF-1395 · Wowdzia et al., 2021 · Medicine & Science in Sports & Exercise · Paper · PubMed

Do elite athletes have worse pregnancies?

Not in 11 studies (2,256 women): no evidence of a difference in birth weight, preterm birth or delivery; less back pain, more excess weight gain. Low to very low certainty; abstract.

Main caveat: Read from the abstract only. How elite was defined, the sports, the included studies, risk of bias and the effect sizes of the outcomes without differences…
moderate evidenceMeasured on highly trained to world-class athletes

Wowdzia and colleagues asked whether women who competed at elite level immediately before conception have different fetal and maternal pregnancy outcomes from active or sedentary women.

They searched online databases to 24 March 2020 for studies of any design and language on pregnant women who "engaged in elite sport immediately before pregnancy", with outcomes from birth weight, low birth weight, macrosomia, preterm birth, fetal heart rate and pulsatility index, caesarean section, instrumental delivery, episiotomy, labour duration and perineal tears to pregnancy low back pain, pelvic girdle pain, urinary incontinence, miscarriage, prenatal weight gain and maternal depression or anxiety.

Eleven unique studies with 2,256 women were included. Elite athletes had lower odds of low back pain in pregnancy (248 women; OR 0.38, 95% CI 0.20-0.73; I² 0%; low certainty) and higher odds of excessive prenatal weight gain (1,763 women; OR 2.47, 95% CI 1.26-4.85; I² 0%; very low certainty).

Two studies with 7 women reported three episodes of fetal bradycardia after high-intensity exercise, which resolved within 10 min of stopping (low certainty). No study reported inadequate weight gain or maternal depression or anxiety. For all other outcomes there were no differences between elite athletes and controls.

The authors conclude that more research is needed before strong statements can be made on how elite sport before pregnancy affects outcomes.

Our reading: this is the only pooled comparison of elite athletes with other women in the base, and it finds no sign of worse birth or delivery outcomes; it says nothing about which training loads during pregnancy are safe, because the exposure is who the women were, not what they did while pregnant, and the certainty is low throughout.

Protocol

Design: systematic review and meta-analysis, PROSPERO CRD42020167382; studies of any design and language; online databases searched up to 24 March 2020.
Population: pregnant women; exposure: elite or competitive sport immediately before pregnancy ("elite athletes who had participated in competitive sport immediately before conception"); comparators: active or sedentary controls.
Outcomes searched: birth weight, low birth weight, macrosomia, preterm birth, fetal heart rate and pulsatility index, caesarean section, instrumental delivery, episiotomy, labour duration, perineal tears, pregnancy-induced low back pain, pelvic girdle pain, urinary incontinence, miscarriage, prenatal weight gain, inadequate or excessive prenatal weight gain, maternal depression or anxiety.
Included: n = 2256 women in 11 unique studies; numbers per outcome as below.
Certainty: graded low or very low for the findings the abstract reports (the grading system is not named in the abstract; the wording matches GRADE).
Not in the abstract: how elite status was defined, the sports, the study designs and dates, training in pregnancy, trimesters, the risk-of-bias tool, effect sizes and CIs for the outcomes without differences.
Funding and interests: not stated in the abstract or the PubMed record (PubMed lists "Research Support, Non-U.S. Gov't" without naming a funder); Crossref lists no funder. No device maker, federation or data platform is named. Mottola and Davenport are also authors of the 2019 Canadian pregnancy guideline (REF-568); that is an author overlap, not a declared conflict.

Key Results

Outcome, elite athletes vs active/sedentary controlsWomenEffect (95% CI)Certainty
Pregnancy low back pain248OR 0.38 (0.20-0.73), I² 0%low
Excessive prenatal weight gain1,763OR 2.47 (1.26-4.85), I² 0%very low
Fetal bradycardia after high-intensity exercise7 (2 studies)3 episodes, resolved within 10 min of stoppinglow
Birth weight, low birth weight, macrosomia, preterm birth, fetal heart rate and pulsatility index, caesarean, instrumental delivery, episiotomy, labour duration, perineal tears, pelvic girdle pain, urinary incontinence, miscarriagenot givenno differences (no effect sizes or CIs in the abstract)not given
Inadequate prenatal weight gain; maternal depression or anxiety—no study reported them—
Reading the nulls: for the outcomes with no differences the abstract gives neither effect sizes nor confidence intervals, so this is no evidence of a difference, of unknown precision; with 11 mostly small studies, a modest difference in an uncommon outcome such as preterm birth cannot be ruled out from the abstract.
The bradycardia line: three episodes in 7 women from two studies, after high-intensity exercise, all resolved within 10 min of stopping; the abstract does not name the studies, the intensity or how the fetal heart rate was recorded.

Mechanisms

Measured (in the pooled studies): fewer reports of pregnancy low back pain and more excessive weight gain in women who were elite athletes before conception; transient fetal bradycardia after high-intensity exercise in a handful of women.
Authors' interpretation: the evidence is too weak to say how elite sport before pregnancy affects maternal and fetal outcomes; more research is needed.
Inference: less low back pain fits better trunk and hip conditioning carried into pregnancy, and more excessive weight gain fits a sharp fall in training energy expenditure without a matching fall in intake; the abstract tests neither explanation.The 7 women are most likely REF-1400's six Olympic athletes plus a 1991 single-athlete case report (both are in this review's reference list, Europe PMC; the abstract does not name the two studies), so REF-1400 is probably part of this finding, not independent support for it.

Practical Application

Do elite athletes have worse pregnancies? Not in 11 studies (2,256 women): no evidence of a difference in birth weight, preterm birth or delivery; less back pain, more excess weight gain. Low to very low certainty; abstract.
Being an elite athlete before conception did not go with worse birth or delivery outcomes (B+, from the abstract; observational, low to very low certainty). It does not show that any particular training load in pregnancy is safe: what the women trained while pregnant is not in the abstract.For the general pregnant population, vigorous exercise into the third trimester showed no difference in birth weight or small babies (REF-1396, A-), and governing-body guidance allows previously vigorous exercisers to continue (REF-567).
Very hard efforts were followed by brief fetal bradycardia in a few women: three episodes in 7 women, all resolved within 10 min of stopping (low certainty).Where the stay-under-90%-of-maximum-heart-rate idea comes from, and what it rests on: REF-1400 (6 Olympic athletes, an observation, not a tested limit) and REF-1401 (15 women, 1-min reps peaking near 96% HRmax, no bradycardia before or right after).Not from this paper; the base's own practice: let perceived effort and the talk test govern intensity, and use any limit the obstetric team sets.
Weight gain is worth watching after a sharp drop in training (from this review's very low-certainty finding): elite athletes had higher odds of excessive prenatal weight gain. Not from this paper; the base's own practice: this is a conversation for the obstetric team, never a reason to under-eat in pregnancy.
What it is good for as a source: the only pooled comparison of elite athletes' pregnancy outcomes with other women's. What it does not show: a safe intensity, volume or heart rate in pregnancy; effects by trimester or sport; outcomes in recreational athletes; anything with high certainty.

Limitations

Read from the abstract only. How elite was defined, the sports, the included studies, risk of bias and the effect sizes of the outcomes without differences could not be checked.
Low to very low certainty on every graded finding; the pooled studies are observational comparisons in which elite athletes differ from controls in many ways besides training.
Exposure is status, not dose. Training during pregnancy (volume, intensity, trimester) is not described in the abstract, so no dose-response can be read from it.
Small numbers for rare events. Three bradycardia episodes in 7 women; preterm birth and low birth weight are uncommon, and the abstract gives no CIs for them.
Funding and interests: not stated in the abstract or the PubMed record; Crossref lists no funder.
How this entry was checked and changed
Why this level

(from the abstract) — the design is a registered systematic review with meta-analysis, which the rubric would place at A- for mostly small studies; held at B+ because the pooled studies are observational comparisons of athletes with non-athletes, every pooled finding the abstract grades is low or very low certainty, the bradycardia finding rests on 7 women, and the no-difference findings for the other outcomes come without effect sizes or confidence intervals in the abstract. Read from the abstract (closed access; Europe PMC holds no full text and OpenAlex lists no open copy)